| Message ID | 20220721152314.RFC.1.Ie333b3e4aff6e4a5b58c4aa805e030e561be8773@changeid (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RFC] drm/edid: Make 144 Hz not preferred on Sharp LQ140M1JW46 | expand |
+ sankeerth Hi Doug On 7/21/2022 3:23 PM, Douglas Anderson wrote: > The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > mode is listed first and thus is marked preferred. The EDID decode I > ran says: > > First detailed timing includes the native pixel format and preferred > refresh rate. > > ... > > Detailed Timing Descriptors: > DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > Hfront 48 Hsync 32 Hback 80 Hpol N > Vfront 3 Vsync 5 Vback 69 Vpol N > DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > Hfront 48 Hsync 32 Hback 80 Hpol N > Vfront 3 Vsync 5 Vback 69 Vpol N > > I'm proposing here that the above is actually a bug and that the 60 Hz > mode really should be considered preferred by Linux. > > The argument here is that this is a laptop panel and on a laptop we > know power will always be a concern. Presumably even if someone using > this panel wanted to use 144 Hz for some use cases they would only do > so dynamically and would still want the default to be 60 Hz. > > Let's change the default to 60 Hz using a standard quirk. > > Signed-off-by: Douglas Anderson <dianders@chromium.org> Yes, we were aware that 144Hz was getting picked. We found that while debugging the screen corruption issue. Well, yes power would be less with 60Hz but so will be the performance. The test teams have been validating with 144Hz so far so we are checking internally with the team whether its OKAY to goto 60Hz now since that kind of invalidates the testing they have been doing. Will update this thread once we finalize. > --- > > drivers/gpu/drm/drm_edid.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c > index bbc25e3b7220..06ff8ba216af 100644 > --- a/drivers/gpu/drm/drm_edid.c > +++ b/drivers/gpu/drm/drm_edid.c > @@ -160,6 +160,9 @@ static const struct edid_quirk { > EDID_QUIRK('S', 'A', 'M', 596, EDID_QUIRK_PREFER_LARGE_60), > EDID_QUIRK('S', 'A', 'M', 638, EDID_QUIRK_PREFER_LARGE_60), > > + /* 144 Hz should only be used when needed; it wastes power */ > + EDID_QUIRK('S', 'H', 'P', 0x1523, EDID_QUIRK_PREFER_LARGE_60), > + > /* Sony PVM-2541A does up to 12 bpc, but only reports max 8 bpc */ > EDID_QUIRK('S', 'N', 'Y', 0x2541, EDID_QUIRK_FORCE_12BPC), >
Hi, On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > + sankeerth > > Hi Doug > > On 7/21/2022 3:23 PM, Douglas Anderson wrote: > > The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > > board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > > mode is listed first and thus is marked preferred. The EDID decode I > > ran says: > > > > First detailed timing includes the native pixel format and preferred > > refresh rate. > > > > ... > > > > Detailed Timing Descriptors: > > DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > > Hfront 48 Hsync 32 Hback 80 Hpol N > > Vfront 3 Vsync 5 Vback 69 Vpol N > > DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > > Hfront 48 Hsync 32 Hback 80 Hpol N > > Vfront 3 Vsync 5 Vback 69 Vpol N > > > > I'm proposing here that the above is actually a bug and that the 60 Hz > > mode really should be considered preferred by Linux. > > > > The argument here is that this is a laptop panel and on a laptop we > > know power will always be a concern. Presumably even if someone using > > this panel wanted to use 144 Hz for some use cases they would only do > > so dynamically and would still want the default to be 60 Hz. > > > > Let's change the default to 60 Hz using a standard quirk. > > > > Signed-off-by: Douglas Anderson <dianders@chromium.org> > > Yes, we were aware that 144Hz was getting picked. We found that while > debugging the screen corruption issue. > > Well, yes power would be less with 60Hz but so will be the performance. What performance specifically will be less with 60 Hz? In general the sc7280 CPU is a bit memory-bandwidth constrained and the LCD refresh from memory is a non-trivial part of that. Reducing to 60 Hz will relieve some of the memory bandwidth pressure and will actually allow tasks on the CPU to run _faster_. I guess the downside is that some animations might be a little less smooth... > The test teams have been validating with 144Hz so far so we are checking > internally with the team whether its OKAY to goto 60Hz now since that > kind of invalidates the testing they have been doing. You're worried that the panel itself won't work well at 60 Hz, or something else about the system won't? The whole system in general needs to work well with 60 Hz displays and I expect them to be much more common than 144 Hz displays. Quite honestly if switching to 60 Hz uncovers a problem that would be a huge benefit of landing this patch because it would mean we'd find it now rather than down the road when someone hooks up a different panel. -Doug
On Fri, Jul 22, 2022 at 9:48 AM Doug Anderson <dianders@chromium.org> wrote: > > Hi, > > On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > > > + sankeerth > > > > Hi Doug > > > > On 7/21/2022 3:23 PM, Douglas Anderson wrote: > > > The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > > > board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > > > mode is listed first and thus is marked preferred. The EDID decode I > > > ran says: > > > > > > First detailed timing includes the native pixel format and preferred > > > refresh rate. > > > > > > ... > > > > > > Detailed Timing Descriptors: > > > DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > > > Hfront 48 Hsync 32 Hback 80 Hpol N > > > Vfront 3 Vsync 5 Vback 69 Vpol N > > > DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > > > Hfront 48 Hsync 32 Hback 80 Hpol N > > > Vfront 3 Vsync 5 Vback 69 Vpol N > > > > > > I'm proposing here that the above is actually a bug and that the 60 Hz > > > mode really should be considered preferred by Linux. > > > > > > The argument here is that this is a laptop panel and on a laptop we > > > know power will always be a concern. Presumably even if someone using > > > this panel wanted to use 144 Hz for some use cases they would only do > > > so dynamically and would still want the default to be 60 Hz. > > > > > > Let's change the default to 60 Hz using a standard quirk. > > > > > > Signed-off-by: Douglas Anderson <dianders@chromium.org> > > > > Yes, we were aware that 144Hz was getting picked. We found that while > > debugging the screen corruption issue. > > > > Well, yes power would be less with 60Hz but so will be the performance. > > What performance specifically will be less with 60 Hz? In general the > sc7280 CPU is a bit memory-bandwidth constrained and the LCD refresh > from memory is a non-trivial part of that. Reducing to 60 Hz will > relieve some of the memory bandwidth pressure and will actually allow > tasks on the CPU to run _faster_. I guess the downside is that some > animations might be a little less smooth... I guess he is referring to something that is vblank sync'd running faster than 60fps. but OTOH it is a bit of a waste for fbcon to be using 144Hz. And there are enough android games that limit themselves to 30fps to save your "phone" battery. So it seems a lot more sane to default to 60Hz and let userspace that knows it wants more pick the 144Hz rate when needed. BR, -R > > > > The test teams have been validating with 144Hz so far so we are checking > > internally with the team whether its OKAY to goto 60Hz now since that > > kind of invalidates the testing they have been doing. > > You're worried that the panel itself won't work well at 60 Hz, or > something else about the system won't? The whole system in general > needs to work well with 60 Hz displays and I expect them to be much > more common than 144 Hz displays. Quite honestly if switching to 60 Hz > uncovers a problem that would be a huge benefit of landing this patch > because it would mean we'd find it now rather than down the road when > someone hooks up a different panel. > > -Doug
Hi Rob and Doug On 7/22/2022 10:36 AM, Rob Clark wrote: > On Fri, Jul 22, 2022 at 9:48 AM Doug Anderson <dianders@chromium.org> wrote: >> >> Hi, >> >> On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: >>> >>> + sankeerth >>> >>> Hi Doug >>> >>> On 7/21/2022 3:23 PM, Douglas Anderson wrote: >>>> The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference >>>> board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz >>>> mode is listed first and thus is marked preferred. The EDID decode I >>>> ran says: >>>> >>>> First detailed timing includes the native pixel format and preferred >>>> refresh rate. >>>> >>>> ... >>>> >>>> Detailed Timing Descriptors: >>>> DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz >>>> Hfront 48 Hsync 32 Hback 80 Hpol N >>>> Vfront 3 Vsync 5 Vback 69 Vpol N >>>> DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz >>>> Hfront 48 Hsync 32 Hback 80 Hpol N >>>> Vfront 3 Vsync 5 Vback 69 Vpol N >>>> >>>> I'm proposing here that the above is actually a bug and that the 60 Hz >>>> mode really should be considered preferred by Linux. Its a bit tricky to say that this is a bug but I think we can certainly add here that for an internal display we would have ideally had the lower resolution first to indicate it as default. >>>> >>>> The argument here is that this is a laptop panel and on a laptop we >>>> know power will always be a concern. Presumably even if someone using >>>> this panel wanted to use 144 Hz for some use cases they would only do >>>> so dynamically and would still want the default to be 60 Hz. >>>> >>>> Let's change the default to 60 Hz using a standard quirk. >>>> >>>> Signed-off-by: Douglas Anderson <dianders@chromium.org> >>> >>> Yes, we were aware that 144Hz was getting picked. We found that while >>> debugging the screen corruption issue. >>> >>> Well, yes power would be less with 60Hz but so will be the performance. >> >> What performance specifically will be less with 60 Hz? In general the >> sc7280 CPU is a bit memory-bandwidth constrained and the LCD refresh >> from memory is a non-trivial part of that. Reducing to 60 Hz will >> relieve some of the memory bandwidth pressure and will actually allow >> tasks on the CPU to run _faster_. I guess the downside is that some >> animations might be a little less smooth... > > I guess he is referring to something that is vblank sync'd running > faster than 60fps. > > but OTOH it is a bit of a waste for fbcon to be using 144Hz. And > there are enough android games that limit themselves to 30fps to save > your "phone" battery. So it seems a lot more sane to default to 60Hz > and let userspace that knows it wants more pick the 144Hz rate when > needed. > > BR, > -R Yes i was referring to vblank synced apps. > >> >> >>> The test teams have been validating with 144Hz so far so we are checking >>> internally with the team whether its OKAY to goto 60Hz now since that >>> kind of invalidates the testing they have been doing. >> >> You're worried that the panel itself won't work well at 60 Hz, or >> something else about the system won't? The whole system in general >> needs to work well with 60 Hz displays and I expect them to be much >> more common than 144 Hz displays. Quite honestly if switching to 60 Hz >> uncovers a problem that would be a huge benefit of landing this patch >> because it would mean we'd find it now rather than down the road when >> someone hooks up a different panel. I was worried that it will invalidate the testing they did so far but since you have confirmed that you would prefer 60Hz to be more thoroughly tested than 144Hz, I have informed the internal teams of this change and given the heads up. You can have my R-b for this change, Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com> I would also wait to see if others have different thought about this. >> >> -Doug
Hi, On Thu, Jul 28, 2022 at 10:34 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > Hi Rob and Doug > > On 7/22/2022 10:36 AM, Rob Clark wrote: > > On Fri, Jul 22, 2022 at 9:48 AM Doug Anderson <dianders@chromium.org> wrote: > >> > >> Hi, > >> > >> On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > >>> > >>> + sankeerth > >>> > >>> Hi Doug > >>> > >>> On 7/21/2022 3:23 PM, Douglas Anderson wrote: > >>>> The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > >>>> board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > >>>> mode is listed first and thus is marked preferred. The EDID decode I > >>>> ran says: > >>>> > >>>> First detailed timing includes the native pixel format and preferred > >>>> refresh rate. > >>>> > >>>> ... > >>>> > >>>> Detailed Timing Descriptors: > >>>> DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > >>>> DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > >>>> > >>>> I'm proposing here that the above is actually a bug and that the 60 Hz > >>>> mode really should be considered preferred by Linux. > > Its a bit tricky to say that this is a bug but I think we can certainly > add here that for an internal display we would have ideally had the > lower resolution first to indicate it as default. Yeah, it gets into the vagueness of the EDID spec in general. As far as I can find it's really up to the monitor to decide by what means it chooses the "preferred" refresh rate if the monitor can support many. Some displays may decide that the normal rate is "preferred" and some may decide that the high refresh rate is "preferred". Neither display is "wrong" per say, but it's nice to have some consistency here and to make it so that otherwise "dumb" userspace will get something reasonable by default. I'll change it to say: While the EDID spec appears to allow a display to use any criteria for picking which refresh mode is "preferred" or "optimal", that vagueness is a bit annoying. From Linux's point of view let's choose the 60 Hz one as the default. > >>>> The argument here is that this is a laptop panel and on a laptop we > >>>> know power will always be a concern. Presumably even if someone using > >>>> this panel wanted to use 144 Hz for some use cases they would only do > >>>> so dynamically and would still want the default to be 60 Hz. > >>>> > >>>> Let's change the default to 60 Hz using a standard quirk. > >>>> > >>>> Signed-off-by: Douglas Anderson <dianders@chromium.org> > >>> > >>> Yes, we were aware that 144Hz was getting picked. We found that while > >>> debugging the screen corruption issue. > >>> > >>> Well, yes power would be less with 60Hz but so will be the performance. > >> > >> What performance specifically will be less with 60 Hz? In general the > >> sc7280 CPU is a bit memory-bandwidth constrained and the LCD refresh > >> from memory is a non-trivial part of that. Reducing to 60 Hz will > >> relieve some of the memory bandwidth pressure and will actually allow > >> tasks on the CPU to run _faster_. I guess the downside is that some > >> animations might be a little less smooth... > > > > I guess he is referring to something that is vblank sync'd running > > faster than 60fps. > > > > but OTOH it is a bit of a waste for fbcon to be using 144Hz. And > > there are enough android games that limit themselves to 30fps to save > > your "phone" battery. So it seems a lot more sane to default to 60Hz > > and let userspace that knows it wants more pick the 144Hz rate when > > needed. > > > > BR, > > -R > > Yes i was referring to vblank synced apps. > > > > >> > >> > >>> The test teams have been validating with 144Hz so far so we are checking > >>> internally with the team whether its OKAY to goto 60Hz now since that > >>> kind of invalidates the testing they have been doing. > >> > >> You're worried that the panel itself won't work well at 60 Hz, or > >> something else about the system won't? The whole system in general > >> needs to work well with 60 Hz displays and I expect them to be much > >> more common than 144 Hz displays. Quite honestly if switching to 60 Hz > >> uncovers a problem that would be a huge benefit of landing this patch > >> because it would mean we'd find it now rather than down the road when > >> someone hooks up a different panel. > > I was worried that it will invalidate the testing they did so far but > since you have confirmed that you would prefer 60Hz to be more > thoroughly tested than 144Hz, I have informed the internal teams of this > change and given the heads up. > > You can have my R-b for this change, > > Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com> > > I would also wait to see if others have different thought about this. Thanks! I'll probably wait another week or so then I'll land in drm-misc-next with your tag. -Doug
On Thu, Jul 28, 2022 at 02:18:38PM -0700, Doug Anderson wrote: > Hi, > > On Thu, Jul 28, 2022 at 10:34 AM Abhinav Kumar > <quic_abhinavk@quicinc.com> wrote: > > > > Hi Rob and Doug > > > > On 7/22/2022 10:36 AM, Rob Clark wrote: > > > On Fri, Jul 22, 2022 at 9:48 AM Doug Anderson <dianders@chromium.org> wrote: > > >> > > >> Hi, > > >> > > >> On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > >>> > > >>> + sankeerth > > >>> > > >>> Hi Doug > > >>> > > >>> On 7/21/2022 3:23 PM, Douglas Anderson wrote: > > >>>> The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > > >>>> board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > > >>>> mode is listed first and thus is marked preferred. The EDID decode I > > >>>> ran says: > > >>>> > > >>>> First detailed timing includes the native pixel format and preferred > > >>>> refresh rate. > > >>>> > > >>>> ... > > >>>> > > >>>> Detailed Timing Descriptors: > > >>>> DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > >>>> DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > >>>> > > >>>> I'm proposing here that the above is actually a bug and that the 60 Hz > > >>>> mode really should be considered preferred by Linux. > > > > Its a bit tricky to say that this is a bug but I think we can certainly > > add here that for an internal display we would have ideally had the > > lower resolution first to indicate it as default. > > Yeah, it gets into the vagueness of the EDID spec in general. As far > as I can find it's really up to the monitor to decide by what means it > chooses the "preferred" refresh rate if the monitor can support many. > Some displays may decide that the normal rate is "preferred" and some > may decide that the high refresh rate is "preferred". Neither display > is "wrong" per say, but it's nice to have some consistency here and to > make it so that otherwise "dumb" userspace will get something > reasonable by default. I'll change it to say: > > While the EDID spec appears to allow a display to use any criteria for > picking which refresh mode is "preferred" or "optimal", that vagueness > is a bit annoying. From Linux's point of view let's choose the 60 Hz > one as the default. And if we start making that decision, it should be for all panels with a similar constraint, so most likely handled by the core, and the new policy properly documented. Doing that just for a single panel is weird. Maxime
Hi, On Fri, Jul 29, 2022 at 12:51 AM Maxime Ripard <maxime@cerno.tech> wrote: > > On Thu, Jul 28, 2022 at 02:18:38PM -0700, Doug Anderson wrote: > > Hi, > > > > On Thu, Jul 28, 2022 at 10:34 AM Abhinav Kumar > > <quic_abhinavk@quicinc.com> wrote: > > > > > > Hi Rob and Doug > > > > > > On 7/22/2022 10:36 AM, Rob Clark wrote: > > > > On Fri, Jul 22, 2022 at 9:48 AM Doug Anderson <dianders@chromium.org> wrote: > > > >> > > > >> Hi, > > > >> > > > >> On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > > >>> > > > >>> + sankeerth > > > >>> > > > >>> Hi Doug > > > >>> > > > >>> On 7/21/2022 3:23 PM, Douglas Anderson wrote: > > > >>>> The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > > > >>>> board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > > > >>>> mode is listed first and thus is marked preferred. The EDID decode I > > > >>>> ran says: > > > >>>> > > > >>>> First detailed timing includes the native pixel format and preferred > > > >>>> refresh rate. > > > >>>> > > > >>>> ... > > > >>>> > > > >>>> Detailed Timing Descriptors: > > > >>>> DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > > >>>> DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > > >>>> > > > >>>> I'm proposing here that the above is actually a bug and that the 60 Hz > > > >>>> mode really should be considered preferred by Linux. > > > > > > Its a bit tricky to say that this is a bug but I think we can certainly > > > add here that for an internal display we would have ideally had the > > > lower resolution first to indicate it as default. > > > > Yeah, it gets into the vagueness of the EDID spec in general. As far > > as I can find it's really up to the monitor to decide by what means it > > chooses the "preferred" refresh rate if the monitor can support many. > > Some displays may decide that the normal rate is "preferred" and some > > may decide that the high refresh rate is "preferred". Neither display > > is "wrong" per say, but it's nice to have some consistency here and to > > make it so that otherwise "dumb" userspace will get something > > reasonable by default. I'll change it to say: > > > > While the EDID spec appears to allow a display to use any criteria for > > picking which refresh mode is "preferred" or "optimal", that vagueness > > is a bit annoying. From Linux's point of view let's choose the 60 Hz > > one as the default. > > And if we start making that decision, it should be for all panels with a > similar constraint, so most likely handled by the core, and the new > policy properly documented. > > Doing that just for a single panel is weird. Yeah, though having a "general policy" in the core can be problematic. In general I think panel EDIDs are only trustworthy as far as you can throw them. They are notorious for having wrong and incorrect information, which is why the EDID quirk list exists to begin with. Trying to change how we're going to interpret all EDIDs, even all EDIDs for eDP panels, seems like it will break someone somewhere. Maybe there are EDIDs out there that were only ever validated at the higher refresh rate and they don't work / flicker / cause digitizer noise at the lower refresh rate. Heck, we've seen eDP panel vendors that can't even get their checksum correct, so I'm not sure I want to make a global assertion that all panels validated their "secondary" display mode. In this particular case, we have validated that this particular Sharp panel works fine at the lower refresh rate. I would also note that, as far as I understand it, ODMs actually can request different EDIDs from the panel vendors. In the past we have been able to get panel vendors to change EDIDs. Thus for most panels I'd expect that we would discover this early, change the EDID default, and be done with it. The case here is a little unusual in that by the time we got involved and started digging into this panel too many were created and nobody wants to throw away those old panels. This is why I'm treating it as a quirk/bug. Really: we should have updated the EDID of the panel but we're unable to in this case. -Doug
On Fri, Jul 29, 2022 at 07:50:20AM -0700, Doug Anderson wrote: > On Fri, Jul 29, 2022 at 12:51 AM Maxime Ripard <maxime@cerno.tech> wrote: > > > > On Thu, Jul 28, 2022 at 02:18:38PM -0700, Doug Anderson wrote: > > > Hi, > > > > > > On Thu, Jul 28, 2022 at 10:34 AM Abhinav Kumar > > > <quic_abhinavk@quicinc.com> wrote: > > > > > > > > Hi Rob and Doug > > > > > > > > On 7/22/2022 10:36 AM, Rob Clark wrote: > > > > > On Fri, Jul 22, 2022 at 9:48 AM Doug Anderson <dianders@chromium.org> wrote: > > > > >> > > > > >> Hi, > > > > >> > > > > >> On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > > > >>> > > > > >>> + sankeerth > > > > >>> > > > > >>> Hi Doug > > > > >>> > > > > >>> On 7/21/2022 3:23 PM, Douglas Anderson wrote: > > > > >>>> The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > > > > >>>> board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > > > > >>>> mode is listed first and thus is marked preferred. The EDID decode I > > > > >>>> ran says: > > > > >>>> > > > > >>>> First detailed timing includes the native pixel format and preferred > > > > >>>> refresh rate. > > > > >>>> > > > > >>>> ... > > > > >>>> > > > > >>>> Detailed Timing Descriptors: > > > > >>>> DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > > > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > > > >>>> DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > > > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > > > >>>> > > > > >>>> I'm proposing here that the above is actually a bug and that the 60 Hz > > > > >>>> mode really should be considered preferred by Linux. > > > > > > > > Its a bit tricky to say that this is a bug but I think we can certainly > > > > add here that for an internal display we would have ideally had the > > > > lower resolution first to indicate it as default. > > > > > > Yeah, it gets into the vagueness of the EDID spec in general. As far > > > as I can find it's really up to the monitor to decide by what means it > > > chooses the "preferred" refresh rate if the monitor can support many. > > > Some displays may decide that the normal rate is "preferred" and some > > > may decide that the high refresh rate is "preferred". Neither display > > > is "wrong" per say, but it's nice to have some consistency here and to > > > make it so that otherwise "dumb" userspace will get something > > > reasonable by default. I'll change it to say: > > > > > > While the EDID spec appears to allow a display to use any criteria for > > > picking which refresh mode is "preferred" or "optimal", that vagueness > > > is a bit annoying. From Linux's point of view let's choose the 60 Hz > > > one as the default. > > > > And if we start making that decision, it should be for all panels with a > > similar constraint, so most likely handled by the core, and the new > > policy properly documented. > > > > Doing that just for a single panel is weird. > > Yeah, though having a "general policy" in the core can be problematic. > > In general I think panel EDIDs are only trustworthy as far as you can > throw them. They are notorious for having wrong and incorrect > information, which is why the EDID quirk list exists to begin with. > Trying to change how we're going to interpret all EDIDs, even all > EDIDs for eDP panels, seems like it will break someone somewhere. > Maybe there are EDIDs out there that were only ever validated at the > higher refresh rate and they don't work / flicker / cause digitizer > noise at the lower refresh rate. Heck, we've seen eDP panel vendors > that can't even get their checksum correct, so I'm not sure I want to > make a global assertion that all panels validated their "secondary" > display mode. > > In this particular case, we have validated that this particular Sharp > panel works fine at the lower refresh rate. > > I would also note that, as far as I understand it, ODMs actually can > request different EDIDs from the panel vendors. In the past we have > been able to get panel vendors to change EDIDs. Thus for most panels > I'd expect that we would discover this early, change the EDID default, > and be done with it. The case here is a little unusual in that by the > time we got involved and started digging into this panel too many were > created and nobody wants to throw away those old panels. This is why > I'm treating it as a quirk/bug. Really: we should have updated the > EDID of the panel but we're unable to in this case. You raise some good points, but most of the discussion around that patch were mostly around performances, power consumption and so on. This is very much a policy decision, and if there is some panel where the EDID reports 60Hz but is broken, then that panel should be the exception to the policy But doing it for a single panel is just odd Maxime
Hi, On Fri, Jul 29, 2022 at 9:41 AM Maxime Ripard <maxime@cerno.tech> wrote: > > On Fri, Jul 29, 2022 at 07:50:20AM -0700, Doug Anderson wrote: > > On Fri, Jul 29, 2022 at 12:51 AM Maxime Ripard <maxime@cerno.tech> wrote: > > > > > > On Thu, Jul 28, 2022 at 02:18:38PM -0700, Doug Anderson wrote: > > > > Hi, > > > > > > > > On Thu, Jul 28, 2022 at 10:34 AM Abhinav Kumar > > > > <quic_abhinavk@quicinc.com> wrote: > > > > > > > > > > Hi Rob and Doug > > > > > > > > > > On 7/22/2022 10:36 AM, Rob Clark wrote: > > > > > > On Fri, Jul 22, 2022 at 9:48 AM Doug Anderson <dianders@chromium.org> wrote: > > > > > >> > > > > > >> Hi, > > > > > >> > > > > > >> On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > > > > >>> > > > > > >>> + sankeerth > > > > > >>> > > > > > >>> Hi Doug > > > > > >>> > > > > > >>> On 7/21/2022 3:23 PM, Douglas Anderson wrote: > > > > > >>>> The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > > > > > >>>> board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > > > > > >>>> mode is listed first and thus is marked preferred. The EDID decode I > > > > > >>>> ran says: > > > > > >>>> > > > > > >>>> First detailed timing includes the native pixel format and preferred > > > > > >>>> refresh rate. > > > > > >>>> > > > > > >>>> ... > > > > > >>>> > > > > > >>>> Detailed Timing Descriptors: > > > > > >>>> DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > > > > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > > > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > > > > >>>> DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > > > > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > > > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > > > > >>>> > > > > > >>>> I'm proposing here that the above is actually a bug and that the 60 Hz > > > > > >>>> mode really should be considered preferred by Linux. > > > > > > > > > > Its a bit tricky to say that this is a bug but I think we can certainly > > > > > add here that for an internal display we would have ideally had the > > > > > lower resolution first to indicate it as default. > > > > > > > > Yeah, it gets into the vagueness of the EDID spec in general. As far > > > > as I can find it's really up to the monitor to decide by what means it > > > > chooses the "preferred" refresh rate if the monitor can support many. > > > > Some displays may decide that the normal rate is "preferred" and some > > > > may decide that the high refresh rate is "preferred". Neither display > > > > is "wrong" per say, but it's nice to have some consistency here and to > > > > make it so that otherwise "dumb" userspace will get something > > > > reasonable by default. I'll change it to say: > > > > > > > > While the EDID spec appears to allow a display to use any criteria for > > > > picking which refresh mode is "preferred" or "optimal", that vagueness > > > > is a bit annoying. From Linux's point of view let's choose the 60 Hz > > > > one as the default. > > > > > > And if we start making that decision, it should be for all panels with a > > > similar constraint, so most likely handled by the core, and the new > > > policy properly documented. > > > > > > Doing that just for a single panel is weird. > > > > Yeah, though having a "general policy" in the core can be problematic. > > > > In general I think panel EDIDs are only trustworthy as far as you can > > throw them. They are notorious for having wrong and incorrect > > information, which is why the EDID quirk list exists to begin with. > > Trying to change how we're going to interpret all EDIDs, even all > > EDIDs for eDP panels, seems like it will break someone somewhere. > > Maybe there are EDIDs out there that were only ever validated at the > > higher refresh rate and they don't work / flicker / cause digitizer > > noise at the lower refresh rate. Heck, we've seen eDP panel vendors > > that can't even get their checksum correct, so I'm not sure I want to > > make a global assertion that all panels validated their "secondary" > > display mode. > > > > In this particular case, we have validated that this particular Sharp > > panel works fine at the lower refresh rate. > > > > I would also note that, as far as I understand it, ODMs actually can > > request different EDIDs from the panel vendors. In the past we have > > been able to get panel vendors to change EDIDs. Thus for most panels > > I'd expect that we would discover this early, change the EDID default, > > and be done with it. The case here is a little unusual in that by the > > time we got involved and started digging into this panel too many were > > created and nobody wants to throw away those old panels. This is why > > I'm treating it as a quirk/bug. Really: we should have updated the > > EDID of the panel but we're unable to in this case. > > You raise some good points, but most of the discussion around that patch > were mostly around performances, power consumption and so on. > > This is very much a policy decision, and if there is some panel where > the EDID reports 60Hz but is broken, then that panel should be the > exception to the policy > > But doing it for a single panel is just odd OK, fair enough. I'll abandon this patch at least as far as mainline is concerned, then. -Doug
On Fri, Jul 29, 2022 at 12:57:40PM -0700, Doug Anderson wrote: > Hi, > > On Fri, Jul 29, 2022 at 9:41 AM Maxime Ripard <maxime@cerno.tech> wrote: > > > > On Fri, Jul 29, 2022 at 07:50:20AM -0700, Doug Anderson wrote: > > > On Fri, Jul 29, 2022 at 12:51 AM Maxime Ripard <maxime@cerno.tech> wrote: > > > > > > > > On Thu, Jul 28, 2022 at 02:18:38PM -0700, Doug Anderson wrote: > > > > > Hi, > > > > > > > > > > On Thu, Jul 28, 2022 at 10:34 AM Abhinav Kumar > > > > > <quic_abhinavk@quicinc.com> wrote: > > > > > > > > > > > > Hi Rob and Doug > > > > > > > > > > > > On 7/22/2022 10:36 AM, Rob Clark wrote: > > > > > > > On Fri, Jul 22, 2022 at 9:48 AM Doug Anderson <dianders@chromium.org> wrote: > > > > > > >> > > > > > > >> Hi, > > > > > > >> > > > > > > >> On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > > > > > >>> > > > > > > >>> + sankeerth > > > > > > >>> > > > > > > >>> Hi Doug > > > > > > >>> > > > > > > >>> On 7/21/2022 3:23 PM, Douglas Anderson wrote: > > > > > > >>>> The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > > > > > > >>>> board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > > > > > > >>>> mode is listed first and thus is marked preferred. The EDID decode I > > > > > > >>>> ran says: > > > > > > >>>> > > > > > > >>>> First detailed timing includes the native pixel format and preferred > > > > > > >>>> refresh rate. > > > > > > >>>> > > > > > > >>>> ... > > > > > > >>>> > > > > > > >>>> Detailed Timing Descriptors: > > > > > > >>>> DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > > > > > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > > > > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > > > > > >>>> DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > > > > > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > > > > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > > > > > >>>> > > > > > > >>>> I'm proposing here that the above is actually a bug and that the 60 Hz > > > > > > >>>> mode really should be considered preferred by Linux. > > > > > > > > > > > > Its a bit tricky to say that this is a bug but I think we can certainly > > > > > > add here that for an internal display we would have ideally had the > > > > > > lower resolution first to indicate it as default. > > > > > > > > > > Yeah, it gets into the vagueness of the EDID spec in general. As far > > > > > as I can find it's really up to the monitor to decide by what means it > > > > > chooses the "preferred" refresh rate if the monitor can support many. > > > > > Some displays may decide that the normal rate is "preferred" and some > > > > > may decide that the high refresh rate is "preferred". Neither display > > > > > is "wrong" per say, but it's nice to have some consistency here and to > > > > > make it so that otherwise "dumb" userspace will get something > > > > > reasonable by default. I'll change it to say: > > > > > > > > > > While the EDID spec appears to allow a display to use any criteria for > > > > > picking which refresh mode is "preferred" or "optimal", that vagueness > > > > > is a bit annoying. From Linux's point of view let's choose the 60 Hz > > > > > one as the default. > > > > > > > > And if we start making that decision, it should be for all panels with a > > > > similar constraint, so most likely handled by the core, and the new > > > > policy properly documented. > > > > > > > > Doing that just for a single panel is weird. > > > > > > Yeah, though having a "general policy" in the core can be problematic. > > > > > > In general I think panel EDIDs are only trustworthy as far as you can > > > throw them. They are notorious for having wrong and incorrect > > > information, which is why the EDID quirk list exists to begin with. > > > Trying to change how we're going to interpret all EDIDs, even all > > > EDIDs for eDP panels, seems like it will break someone somewhere. > > > Maybe there are EDIDs out there that were only ever validated at the > > > higher refresh rate and they don't work / flicker / cause digitizer > > > noise at the lower refresh rate. Heck, we've seen eDP panel vendors > > > that can't even get their checksum correct, so I'm not sure I want to > > > make a global assertion that all panels validated their "secondary" > > > display mode. > > > > > > In this particular case, we have validated that this particular Sharp > > > panel works fine at the lower refresh rate. > > > > > > I would also note that, as far as I understand it, ODMs actually can > > > request different EDIDs from the panel vendors. In the past we have > > > been able to get panel vendors to change EDIDs. Thus for most panels > > > I'd expect that we would discover this early, change the EDID default, > > > and be done with it. The case here is a little unusual in that by the > > > time we got involved and started digging into this panel too many were > > > created and nobody wants to throw away those old panels. This is why > > > I'm treating it as a quirk/bug. Really: we should have updated the > > > EDID of the panel but we're unable to in this case. > > > > You raise some good points, but most of the discussion around that patch > > were mostly around performances, power consumption and so on. > > > > This is very much a policy decision, and if there is some panel where > > the EDID reports 60Hz but is broken, then that panel should be the > > exception to the policy > > > > But doing it for a single panel is just odd > > OK, fair enough. I'll abandon this patch at least as far as mainline > is concerned, then. That wasn't really my point though :) If you think that this change is needed, then we should totally discuss it and I'm not opposed to it. What I don't really like about this patch is that it's about a single panel: if we're doing it we should do it for all the panels. Where we do it can also be discussed, but we should remain consistent there. Maxime
Hi, On Sun, Aug 14, 2022 at 11:46 PM Maxime Ripard <maxime@cerno.tech> wrote: > > On Fri, Jul 29, 2022 at 12:57:40PM -0700, Doug Anderson wrote: > > Hi, > > > > On Fri, Jul 29, 2022 at 9:41 AM Maxime Ripard <maxime@cerno.tech> wrote: > > > > > > On Fri, Jul 29, 2022 at 07:50:20AM -0700, Doug Anderson wrote: > > > > On Fri, Jul 29, 2022 at 12:51 AM Maxime Ripard <maxime@cerno.tech> wrote: > > > > > > > > > > On Thu, Jul 28, 2022 at 02:18:38PM -0700, Doug Anderson wrote: > > > > > > Hi, > > > > > > > > > > > > On Thu, Jul 28, 2022 at 10:34 AM Abhinav Kumar > > > > > > <quic_abhinavk@quicinc.com> wrote: > > > > > > > > > > > > > > Hi Rob and Doug > > > > > > > > > > > > > > On 7/22/2022 10:36 AM, Rob Clark wrote: > > > > > > > > On Fri, Jul 22, 2022 at 9:48 AM Doug Anderson <dianders@chromium.org> wrote: > > > > > > > >> > > > > > > > >> Hi, > > > > > > > >> > > > > > > > >> On Fri, Jul 22, 2022 at 9:37 AM Abhinav Kumar <quic_abhinavk@quicinc.com> wrote: > > > > > > > >>> > > > > > > > >>> + sankeerth > > > > > > > >>> > > > > > > > >>> Hi Doug > > > > > > > >>> > > > > > > > >>> On 7/21/2022 3:23 PM, Douglas Anderson wrote: > > > > > > > >>>> The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference > > > > > > > >>>> board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz > > > > > > > >>>> mode is listed first and thus is marked preferred. The EDID decode I > > > > > > > >>>> ran says: > > > > > > > >>>> > > > > > > > >>>> First detailed timing includes the native pixel format and preferred > > > > > > > >>>> refresh rate. > > > > > > > >>>> > > > > > > > >>>> ... > > > > > > > >>>> > > > > > > > >>>> Detailed Timing Descriptors: > > > > > > > >>>> DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz > > > > > > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > > > > > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > > > > > > >>>> DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz > > > > > > > >>>> Hfront 48 Hsync 32 Hback 80 Hpol N > > > > > > > >>>> Vfront 3 Vsync 5 Vback 69 Vpol N > > > > > > > >>>> > > > > > > > >>>> I'm proposing here that the above is actually a bug and that the 60 Hz > > > > > > > >>>> mode really should be considered preferred by Linux. > > > > > > > > > > > > > > Its a bit tricky to say that this is a bug but I think we can certainly > > > > > > > add here that for an internal display we would have ideally had the > > > > > > > lower resolution first to indicate it as default. > > > > > > > > > > > > Yeah, it gets into the vagueness of the EDID spec in general. As far > > > > > > as I can find it's really up to the monitor to decide by what means it > > > > > > chooses the "preferred" refresh rate if the monitor can support many. > > > > > > Some displays may decide that the normal rate is "preferred" and some > > > > > > may decide that the high refresh rate is "preferred". Neither display > > > > > > is "wrong" per say, but it's nice to have some consistency here and to > > > > > > make it so that otherwise "dumb" userspace will get something > > > > > > reasonable by default. I'll change it to say: > > > > > > > > > > > > While the EDID spec appears to allow a display to use any criteria for > > > > > > picking which refresh mode is "preferred" or "optimal", that vagueness > > > > > > is a bit annoying. From Linux's point of view let's choose the 60 Hz > > > > > > one as the default. > > > > > > > > > > And if we start making that decision, it should be for all panels with a > > > > > similar constraint, so most likely handled by the core, and the new > > > > > policy properly documented. > > > > > > > > > > Doing that just for a single panel is weird. > > > > > > > > Yeah, though having a "general policy" in the core can be problematic. > > > > > > > > In general I think panel EDIDs are only trustworthy as far as you can > > > > throw them. They are notorious for having wrong and incorrect > > > > information, which is why the EDID quirk list exists to begin with. > > > > Trying to change how we're going to interpret all EDIDs, even all > > > > EDIDs for eDP panels, seems like it will break someone somewhere. > > > > Maybe there are EDIDs out there that were only ever validated at the > > > > higher refresh rate and they don't work / flicker / cause digitizer > > > > noise at the lower refresh rate. Heck, we've seen eDP panel vendors > > > > that can't even get their checksum correct, so I'm not sure I want to > > > > make a global assertion that all panels validated their "secondary" > > > > display mode. > > > > > > > > In this particular case, we have validated that this particular Sharp > > > > panel works fine at the lower refresh rate. > > > > > > > > I would also note that, as far as I understand it, ODMs actually can > > > > request different EDIDs from the panel vendors. In the past we have > > > > been able to get panel vendors to change EDIDs. Thus for most panels > > > > I'd expect that we would discover this early, change the EDID default, > > > > and be done with it. The case here is a little unusual in that by the > > > > time we got involved and started digging into this panel too many were > > > > created and nobody wants to throw away those old panels. This is why > > > > I'm treating it as a quirk/bug. Really: we should have updated the > > > > EDID of the panel but we're unable to in this case. > > > > > > You raise some good points, but most of the discussion around that patch > > > were mostly around performances, power consumption and so on. > > > > > > This is very much a policy decision, and if there is some panel where > > > the EDID reports 60Hz but is broken, then that panel should be the > > > exception to the policy > > > > > > But doing it for a single panel is just odd > > > > OK, fair enough. I'll abandon this patch at least as far as mainline > > is concerned, then. > > That wasn't really my point though :) > > If you think that this change is needed, then we should totally discuss > it and I'm not opposed to it. > > What I don't really like about this patch is that it's about a single > panel: if we're doing it we should do it for all the panels. > > Where we do it can also be discussed, but we should remain consistent > there. I was never massively confident about it, which is why I added the "RFC" tag to begin with. ;-) In general I suspect that either change will make people upset. In other words, if we programmatically always try to put the "high refresh rate" first for all displays then people will be upset and if we programmatically always try to put the "60 Hz rate" first then people will be upset. Unless someone wants to stand up and say that one side or the other is wrong, I think we're going to simply leave this up to the whim of individual panels. Someone could stand up and demand that it go one way or the other, but I certainly don't have that clout. The spec, as far as I can tell, says that it's up to the panel vendor to use whatever means they want to decide on the "preferred" refresh rate. Thus, as far as the spec is concerned this decision is made on an individual panel basis. ;-) This was really the justification for why my patch was just on one panel. In any case, as I said I'm OK w/ dropping this. We'll find other ways to work around the issue. -Doug
On Wed, 17 Aug 2022, Doug Anderson <dianders@chromium.org> wrote: > Hi, > > On Sun, Aug 14, 2022 at 11:46 PM Maxime Ripard <maxime@cerno.tech> wrote: >> >> On Fri, Jul 29, 2022 at 12:57:40PM -0700, Doug Anderson wrote: >> > Hi, >> > >> > On Fri, Jul 29, 2022 at 9:41 AM Maxime Ripard <maxime@cerno.tech> wrote: >> > > You raise some good points, but most of the discussion around that patch >> > > were mostly around performances, power consumption and so on. >> > > >> > > This is very much a policy decision, and if there is some panel where >> > > the EDID reports 60Hz but is broken, then that panel should be the >> > > exception to the policy >> > > >> > > But doing it for a single panel is just odd >> > >> > OK, fair enough. I'll abandon this patch at least as far as mainline >> > is concerned, then. >> >> That wasn't really my point though :) >> >> If you think that this change is needed, then we should totally discuss >> it and I'm not opposed to it. >> >> What I don't really like about this patch is that it's about a single >> panel: if we're doing it we should do it for all the panels. >> >> Where we do it can also be discussed, but we should remain consistent >> there. > > I was never massively confident about it, which is why I added the > "RFC" tag to begin with. ;-) In general I suspect that either change > will make people upset. In other words, if we programmatically always > try to put the "high refresh rate" first for all displays then people > will be upset and if we programmatically always try to put the "60 Hz > rate" first then people will be upset. Unless someone wants to stand > up and say that one side or the other is wrong, I think we're going to > simply leave this up to the whim of individual panels. Someone could > stand up and demand that it go one way or the other, but I certainly > don't have that clout. > > The spec, as far as I can tell, says that it's up to the panel vendor > to use whatever means they want to decide on the "preferred" refresh > rate. Thus, as far as the spec is concerned this decision is made on > an individual panel basis. ;-) This was really the justification for > why my patch was just on one panel. > > In any case, as I said I'm OK w/ dropping this. We'll find other ways > to work around the issue. FWIW, if the EDID reported preferred mode works, I also think that's what we should prefer. BR, Jani.
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index bbc25e3b7220..06ff8ba216af 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -160,6 +160,9 @@ static const struct edid_quirk { EDID_QUIRK('S', 'A', 'M', 596, EDID_QUIRK_PREFER_LARGE_60), EDID_QUIRK('S', 'A', 'M', 638, EDID_QUIRK_PREFER_LARGE_60), + /* 144 Hz should only be used when needed; it wastes power */ + EDID_QUIRK('S', 'H', 'P', 0x1523, EDID_QUIRK_PREFER_LARGE_60), + /* Sony PVM-2541A does up to 12 bpc, but only reports max 8 bpc */ EDID_QUIRK('S', 'N', 'Y', 0x2541, EDID_QUIRK_FORCE_12BPC),
The Sharp LQ140M1JW46 panel is on the Qualcomm sc7280 CRD reference board. This panel supports 144 Hz and 60 Hz. In the EDID, the 144 Hz mode is listed first and thus is marked preferred. The EDID decode I ran says: First detailed timing includes the native pixel format and preferred refresh rate. ... Detailed Timing Descriptors: DTD 1: 1920x1080 143.981 Hz 16:9 166.587 kHz 346.500 MHz Hfront 48 Hsync 32 Hback 80 Hpol N Vfront 3 Vsync 5 Vback 69 Vpol N DTD 2: 1920x1080 59.990 Hz 16:9 69.409 kHz 144.370 MHz Hfront 48 Hsync 32 Hback 80 Hpol N Vfront 3 Vsync 5 Vback 69 Vpol N I'm proposing here that the above is actually a bug and that the 60 Hz mode really should be considered preferred by Linux. The argument here is that this is a laptop panel and on a laptop we know power will always be a concern. Presumably even if someone using this panel wanted to use 144 Hz for some use cases they would only do so dynamically and would still want the default to be 60 Hz. Let's change the default to 60 Hz using a standard quirk. Signed-off-by: Douglas Anderson <dianders@chromium.org> --- drivers/gpu/drm/drm_edid.c | 3 +++ 1 file changed, 3 insertions(+)