| Message ID | 20220721000658.29537-1-william.zhang@broadcom.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: bcmbca: Move BCM4908 SoC support under ARCH_BCMBCA | expand |
On 2022-07-21 02:06, William Zhang wrote: > Append "brcm,bcmbca" to BCM4908 chip family compatible strings. Add > generic 4908 board entry. > > Signed-off-by: William Zhang <william.zhang@broadcom.com> Acked-by: Rafał Miłecki <rafal@milecki.pl> (with one minor comment below) > --- > > Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git > a/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml > b/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml > index 6a64afa95918..4494a2c58c7f 100644 > --- a/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml > +++ b/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml > @@ -36,18 +36,22 @@ properties: > - tplink,archer-c2300-v1 > - const: brcm,bcm4906 > - const: brcm,bcm4908 > + - const: brcm,bcmbca > > - description: BCM4908 based boards > items: > - enum: > - asus,gt-ac5300 > - netgear,raxe500 > + - brcm,bcm94908 I think it would be nice to keep enum entries sorted > - const: brcm,bcm4908 > + - const: brcm,bcmbca > > - description: BCM49408 based boards > items: > - const: brcm,bcm49408 > - const: brcm,bcm4908 > + - const: brcm,bcmbca > > - description: BCM4912 based boards > items:
On 21/07/2022 02:06, William Zhang wrote: > Append "brcm,bcmbca" to BCM4908 chip family compatible strings. Add > generic 4908 board entry. This does not explain at all why you are doing it. Improve your commit messages. The explanation you gave here: https://lore.kernel.org/all/b8eda882-6838-ab7d-6e2e-131e3125b16f@broadcom.com/ is also not really sufficient (and is not in commit msg). Moving things around in Linux Kconfig does not justify adding some new compatibles. To be - clear - this is not a review, so you cannot add Rb tag. If you insist on a tag, then it as counted as NAK. Best regards, Krzysztof
On 2022-07-21 08:44, Krzysztof Kozlowski wrote: > On 21/07/2022 02:06, William Zhang wrote: >> Append "brcm,bcmbca" to BCM4908 chip family compatible strings. Add >> generic 4908 board entry. > > This does not explain at all why you are doing it. Improve your commit > messages. To clarify it from my side (and maybe help a bit): 1. As I understand it BCMBCA is a one big family of SoCs. 2. BCM4908 is a subset of that family (a subfamily?) designed for a specific group of devices. If that's correct I think William it's what you should describe in your commit message. That would make binding more accurate and should be a good argument for your change (I believe).
On 21/07/2022 08:51, Rafał Miłecki wrote: > On 2022-07-21 08:44, Krzysztof Kozlowski wrote: >> On 21/07/2022 02:06, William Zhang wrote: >>> Append "brcm,bcmbca" to BCM4908 chip family compatible strings. Add >>> generic 4908 board entry. >> >> This does not explain at all why you are doing it. Improve your commit >> messages. > > To clarify it from my side (and maybe help a bit): > > 1. As I understand it BCMBCA is a one big family of SoCs. > 2. BCM4908 is a subset of that family (a subfamily?) designed for a > specific group of devices. > > If that's correct I think William it's what you should describe in your > commit message. That would make binding more accurate and should be a > good argument for your change (I believe). That's better argument. But what's the benefit of adding generic compatible? Devices cannot bind to it (it is too generic). Does it describe the device anyhow? Imagine someone adding compatible "brcm,all-soc-of-broadcom" - does it make any sense? Best regards, Krzysztof
On 2022-07-21 09:01, Krzysztof Kozlowski wrote: > On 21/07/2022 08:51, Rafał Miłecki wrote: >> On 2022-07-21 08:44, Krzysztof Kozlowski wrote: >>> On 21/07/2022 02:06, William Zhang wrote: >>>> Append "brcm,bcmbca" to BCM4908 chip family compatible strings. Add >>>> generic 4908 board entry. >>> >>> This does not explain at all why you are doing it. Improve your >>> commit >>> messages. >> >> To clarify it from my side (and maybe help a bit): >> >> 1. As I understand it BCMBCA is a one big family of SoCs. >> 2. BCM4908 is a subset of that family (a subfamily?) designed for a >> specific group of devices. >> >> If that's correct I think William it's what you should describe in >> your >> commit message. That would make binding more accurate and should be a >> good argument for your change (I believe). > > That's better argument. But what's the benefit of adding generic > compatible? Devices cannot bind to it (it is too generic). Does it > describe the device anyhow? Imagine someone adding compatible > "brcm,all-soc-of-broadcom" - does it make any sense? OK, I see it now. I can't think of any case of handling all devices covered with suc a wide brcm,bcmbca binding. This leads me to another question if we should actually totally drop brcm,bcmbca from other SoCs bindings, see linux-next's Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml
On 21/07/2022 09:13, Rafał Miłecki wrote: >> That's better argument. But what's the benefit of adding generic >> compatible? Devices cannot bind to it (it is too generic). Does it >> describe the device anyhow? Imagine someone adding compatible >> "brcm,all-soc-of-broadcom" - does it make any sense? > > OK, I see it now. I can't think of any case of handling all devices > covered with suc a wide brcm,bcmbca binding. Maybe there is some common part of a SoC which that generic compatible would express? Most archs don't use soc-wide generic compatible, because of reasons I mentioned - no actual benefits for anyone from such compatible. But there are exceptions. I fouun socfpga and apple. The apple sounds as mistake to me, because the generic "apple,arm-platform" compatible looks like covering all possible Apple ARM platforms. I think Apple ARM designs in 20 years will not be compatible at all with current design, so such broad compatible is not useful... but that's only my opinion. > > This leads me to another question if we should actually totally drop > brcm,bcmbca from other SoCs bindings, see linux-next's > Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml This would be tricky as it was already accepted, unless all sit in linux-next and did not make to v5.19-rc1. Best regards, Krzysztof
On 2022-07-21 09:36, Krzysztof Kozlowski wrote: > On 21/07/2022 09:13, Rafał Miłecki wrote: >>> That's better argument. But what's the benefit of adding generic >>> compatible? Devices cannot bind to it (it is too generic). Does it >>> describe the device anyhow? Imagine someone adding compatible >>> "brcm,all-soc-of-broadcom" - does it make any sense? >> >> OK, I see it now. I can't think of any case of handling all devices >> covered with suc a wide brcm,bcmbca binding. > > Maybe there is some common part of a SoC which that generic compatible > would express? > > Most archs don't use soc-wide generic compatible, because of reasons I > mentioned - no actual benefits for anyone from such compatible. > > But there are exceptions. I fouun socfpga and apple. The apple sounds > as > mistake to me, because the generic "apple,arm-platform" compatible > looks > like covering all possible Apple ARM platforms. I think Apple ARM > designs in 20 years will not be compatible at all with current design, > so such broad compatible is not useful... but that's only my opinion. Let's see if William / Broadcom guys can provide a valid argument for the brcm,bcmbca. >> This leads me to another question if we should actually totally drop >> brcm,bcmbca from other SoCs bindings, see linux-next's >> Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml > > This would be tricky as it was already accepted, unless all sit in > linux-next and did not make to v5.19-rc1. 5.19-rc7 has only 1 case with brcm,bcmbca, see ff6992735ade7 ("Linux 5.19-rc7"): https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml?id=ff6992735ade75aae3e35d16b17da1008d753d28 So we can still clean it up for the 5.20-rc1 or 5.20-rc2.
On 7/21/22 00:50, Rafał Miłecki wrote: > On 2022-07-21 09:36, Krzysztof Kozlowski wrote: >> On 21/07/2022 09:13, Rafał Miłecki wrote: >>>> That's better argument. But what's the benefit of adding generic >>>> compatible? Devices cannot bind to it (it is too generic). Does it >>>> describe the device anyhow? Imagine someone adding compatible >>>> "brcm,all-soc-of-broadcom" - does it make any sense? >>> >>> OK, I see it now. I can't think of any case of handling all devices >>> covered with suc a wide brcm,bcmbca binding. >> >> Maybe there is some common part of a SoC which that generic compatible >> would express? >> >> Most archs don't use soc-wide generic compatible, because of reasons I >> mentioned - no actual benefits for anyone from such compatible. >> >> But there are exceptions. I fouun socfpga and apple. The apple sounds as >> mistake to me, because the generic "apple,arm-platform" compatible looks >> like covering all possible Apple ARM platforms. I think Apple ARM >> designs in 20 years will not be compatible at all with current design, >> so such broad compatible is not useful... but that's only my opinion. > > Let's see if William / Broadcom guys can provide a valid argument for > the brcm,bcmbca. It is common practice to provide a generic fallback compatible string for a given chip family/architecture and all of our existing in-tree (and out of tree for that matter) DTSes for Broadcom SoCs do that: - Documentation/devicetree/bindings/arm/bcm/brcm,brcmstb.txt - Documentation/devicetree/bindings/arm/bcm/brcm,ns2.yaml - Documentation/devicetree/bindings/arm/bcm/brcm,nsp.yaml - Documentation/devicetree/bindings/arm/bcm/brcm,cygnus.yaml list goes on and on, of course the counter examples are bcm2835, bcm4708 etc. although those are both chip and families technically, so I suppose the conflation is appropriate in that case. So the pattern is simple: - outside of Broadcom contributors used convention - inside of Broadcom contributors used another so if nothing else, we ought to be consistent within ourselves as Broadcom insiders, which we are doing here. While the generic fallback may not be in use, it still serves a purpose: - Broadcom likes to create a gazillion of part numbers that are hard to untangle from their original SoC architecture unless you happen to work there so it serves as documentation for others to identify what family they belong to, and what to expect from that - you never know when you might want to be matching on just the generic compatible string of a family and putting it in there costs nothing at all The point of William's patch series is to right a number of wrongs on Broadcom's side: - lack of appropriate involvements at the time Rafal submitted the 4908 support as a "standalone" family, I am to take the blame for suggesting that name in the first place, though I did not know at the time that William and others would ever be contributing upstream - avoid the proliferation of "sub" families within a larger family (BCMBCA) since that serves no purpose other than to make it harder on users to select what they should be selecting in their kernel *and* it makes us inconsistent with arch/arm64/Kconfig.platforms that attempts to reduce those I would conclude by asking you: why is this such a big issue? What *actual* problem does it causes, except maybe setting a precedent that you do not like, but for which you practically should have no reason to care as long as the binding is enforced. > > >>> This leads me to another question if we should actually totally drop >>> brcm,bcmbca from other SoCs bindings, see linux-next's >>> Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml >> >> This would be tricky as it was already accepted, unless all sit in >> linux-next and did not make to v5.19-rc1. > > 5.19-rc7 has only 1 case with brcm,bcmbca, see ff6992735ade7 > ("Linux 5.19-rc7"): > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml?id=ff6992735ade75aae3e35d16b17da1008d753d28 > > So we can still clean it up for the 5.20-rc1 or 5.20-rc2. Not so fast.
On 07/21/2022 09:43 AM, Florian Fainelli wrote: > On 7/21/22 00:50, Rafał Miłecki wrote: >> On 2022-07-21 09:36, Krzysztof Kozlowski wrote: >>> On 21/07/2022 09:13, Rafał Miłecki wrote: >>>>> That's better argument. But what's the benefit of adding generic >>>>> compatible? Devices cannot bind to it (it is too generic). Does it >>>>> describe the device anyhow? Imagine someone adding compatible >>>>> "brcm,all-soc-of-broadcom" - does it make any sense? >>>> >>>> OK, I see it now. I can't think of any case of handling all devices >>>> covered with suc a wide brcm,bcmbca binding. >>> >>> Maybe there is some common part of a SoC which that generic compatible >>> would express? >>> >>> Most archs don't use soc-wide generic compatible, because of reasons I >>> mentioned - no actual benefits for anyone from such compatible. >>> >>> But there are exceptions. I fouun socfpga and apple. The apple sounds as >>> mistake to me, because the generic "apple,arm-platform" compatible looks >>> like covering all possible Apple ARM platforms. I think Apple ARM >>> designs in 20 years will not be compatible at all with current design, >>> so such broad compatible is not useful... but that's only my opinion. >> >> Let's see if William / Broadcom guys can provide a valid argument for >> the brcm,bcmbca. > > It is common practice to provide a generic fallback compatible string for a given chip family/architecture and all of our existing in-tree (and out of tree for that matter) DTSes for Broadcom SoCs do that: > > - Documentation/devicetree/bindings/arm/bcm/brcm,brcmstb.txt > - Documentation/devicetree/bindings/arm/bcm/brcm,ns2.yaml > - Documentation/devicetree/bindings/arm/bcm/brcm,nsp.yaml > - Documentation/devicetree/bindings/arm/bcm/brcm,cygnus.yaml > > list goes on and on, of course the counter examples are bcm2835, bcm4708 etc. although those are both chip and families technically, so I suppose the conflation is appropriate in that case. So the pattern is simple: > > - outside of Broadcom contributors used convention > - inside of Broadcom contributors used another > > so if nothing else, we ought to be consistent within ourselves as Broadcom insiders, which we are doing here. > > While the generic fallback may not be in use, it still serves a purpose: > > - Broadcom likes to create a gazillion of part numbers that are hard to untangle from their original SoC architecture unless you happen to work there so it serves as documentation for others to identify what family they belong to, and what to expect from that > > - you never know when you might want to be matching on just the generic compatible string of a family and putting it in there costs nothing at all > > The point of William's patch series is to right a number of wrongs on Broadcom's side: > > - lack of appropriate involvements at the time Rafal submitted the 4908 support as a "standalone" family, I am to take the blame for suggesting that name in the first place, though I did not know at the time that William and others would ever be contributing upstream > > - avoid the proliferation of "sub" families within a larger family (BCMBCA) since that serves no purpose other than to make it harder on users to select what they should be selecting in their kernel *and* it makes us inconsistent with arch/arm64/Kconfig.platforms that attempts to reduce those > > I would conclude by asking you: why is this such a big issue? What *actual* problem does it causes, except maybe setting a precedent that you do not like, but for which you practically should have no reason to care as long as the binding is enforced. > Totally agreed. Just want to emphasize that the main reason of this change to merge all the bcmbca family chips into the same group for better organization and reduce the clutter to the kernel source. Think about 18 bcmbca devices with different changes to yaml, kconfig, makefile, sub-directory while they actually share many common blocks, drivers and dts entries. While nobody would bind a device to brcm,bcmbca (and it can not be binded because bcmbca,yaml require to prefix with a specific chip), it is a great way to make it easy for people to understand what device they are working and look for the bcmbca common driver and other support code as well. Wouldn't this be good thing to have? And don't forget we introduced bcmbca awhile back with first SoC 47622 and have set a clear goal for the purpose we are discussing here today: Please see this patch series: http://lists.infradead.org/pipermail/linux-arm-kernel/2022-April/732867.html "This change introduces Broadcom's ARCH_BCMBCA architecture for armv7 and armv8 based Broadband SoCs. We expect to send additional patches for each SoC in the near future." And Krzysztof acked that yaml for brcm,bcabca here : http://lists.infradead.org/pipermail/linux-arm-kernel/2022-April/732867.html >> >> >>>> This leads me to another question if we should actually totally drop >>>> brcm,bcmbca from other SoCs bindings, see linux-next's >>>> Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml >>> >>> This would be tricky as it was already accepted, unless all sit in >>> linux-next and did not make to v5.19-rc1. >> >> 5.19-rc7 has only 1 case with brcm,bcmbca, see ff6992735ade7 >> ("Linux 5.19-rc7"): >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml?id=ff6992735ade75aae3e35d16b17da1008d753d28 >> >> So we can still clean it up for the 5.20-rc1 or 5.20-rc2. > > Not so fast. >
On 07/21/2022 12:01 AM, Krzysztof Kozlowski wrote: > On 21/07/2022 08:51, Rafał Miłecki wrote: >> On 2022-07-21 08:44, Krzysztof Kozlowski wrote: >>> On 21/07/2022 02:06, William Zhang wrote: >>>> Append "brcm,bcmbca" to BCM4908 chip family compatible strings. Add >>>> generic 4908 board entry. >>> >>> This does not explain at all why you are doing it. Improve your commit >>> messages. >> >> To clarify it from my side (and maybe help a bit): >> >> 1. As I understand it BCMBCA is a one big family of SoCs. >> 2. BCM4908 is a subset of that family (a subfamily?) designed for a >> specific group of devices. >> >> If that's correct I think William it's what you should describe in your >> commit message. That would make binding more accurate and should be a >> good argument for your change (I believe). > > That's better argument. But what's the benefit of adding generic > compatible? Devices cannot bind to it (it is too generic). Does it > describe the device anyhow? Imagine someone adding compatible > "brcm,all-soc-of-broadcom" - does it make any sense? > In case you were also referring the generic 4908 board compatible string brcm,bcm94908, this is for a bare bone 4908 board dts that only enables ARM cpu subsystem, memory and uart. It can be used on all 4908 based Broadcom reference boards and customer board. It is especially useful for initial board bring up and one can load this generic board and start work and debug from the console. Also would be helpful to do a quick verification of new kernel version when there is cpu subsystem related change. I guess my mindset already assume people are now familiar with this model of bcmbca binding addition for a new SoC since we introduced the bcmbca arch with first soc 47622 and 10+ other socs late. But sure I agree and I will update the commit message with more details in addition to what the cover letter says. > Best regards, > Krzysztof >
On 21/07/2022 21:35, William Zhang wrote: > > > On 07/21/2022 09:43 AM, Florian Fainelli wrote: >> On 7/21/22 00:50, Rafał Miłecki wrote: >>> On 2022-07-21 09:36, Krzysztof Kozlowski wrote: >>>> On 21/07/2022 09:13, Rafał Miłecki wrote: >>>>>> That's better argument. But what's the benefit of adding generic >>>>>> compatible? Devices cannot bind to it (it is too generic). Does it >>>>>> describe the device anyhow? Imagine someone adding compatible >>>>>> "brcm,all-soc-of-broadcom" - does it make any sense? > > >>>>> >>>>> OK, I see it now. I can't think of any case of handling all devices >>>>> covered with suc a wide brcm,bcmbca binding. >>>> >>>> Maybe there is some common part of a SoC which that generic compatible >>>> would express? >>>> >>>> Most archs don't use soc-wide generic compatible, because of reasons I >>>> mentioned - no actual benefits for anyone from such compatible. >>>> >>>> But there are exceptions. I fouun socfpga and apple. The apple sounds as >>>> mistake to me, because the generic "apple,arm-platform" compatible looks >>>> like covering all possible Apple ARM platforms. I think Apple ARM >>>> designs in 20 years will not be compatible at all with current design, >>>> so such broad compatible is not useful... but that's only my opinion. >>> >>> Let's see if William / Broadcom guys can provide a valid argument for >>> the brcm,bcmbca. >> >> It is common practice to provide a generic fallback compatible string for a given chip family/architecture and all of our existing in-tree (and out of tree for that matter) DTSes for Broadcom SoCs do that: >> >> - Documentation/devicetree/bindings/arm/bcm/brcm,brcmstb.txt >> - Documentation/devicetree/bindings/arm/bcm/brcm,ns2.yaml >> - Documentation/devicetree/bindings/arm/bcm/brcm,nsp.yaml >> - Documentation/devicetree/bindings/arm/bcm/brcm,cygnus.yaml >> >> list goes on and on, of course the counter examples are bcm2835, bcm4708 etc. although those are both chip and families technically, so I suppose the conflation is appropriate in that case. So the pattern is simple: >> >> - outside of Broadcom contributors used convention >> - inside of Broadcom contributors used another >> >> so if nothing else, we ought to be consistent within ourselves as Broadcom insiders, which we are doing here. >> >> While the generic fallback may not be in use, it still serves a purpose: >> >> - Broadcom likes to create a gazillion of part numbers that are hard to untangle from their original SoC architecture unless you happen to work there so it serves as documentation for others to identify what family they belong to, and what to expect from that >> >> - you never know when you might want to be matching on just the generic compatible string of a family and putting it in there costs nothing at all >> >> The point of William's patch series is to right a number of wrongs on Broadcom's side: >> >> - lack of appropriate involvements at the time Rafal submitted the 4908 support as a "standalone" family, I am to take the blame for suggesting that name in the first place, though I did not know at the time that William and others would ever be contributing upstream >> >> - avoid the proliferation of "sub" families within a larger family (BCMBCA) since that serves no purpose other than to make it harder on users to select what they should be selecting in their kernel *and* it makes us inconsistent with arch/arm64/Kconfig.platforms that attempts to reduce those >> >> I would conclude by asking you: why is this such a big issue? What *actual* problem does it causes, except maybe setting a precedent that you do not like, but for which you practically should have no reason to care as long as the binding is enforced. >> > Totally agreed. Just want to emphasize that the main reason of this > change to merge all the bcmbca family chips into the same group for > better organization and reduce the clutter to the kernel source. Think > about 18 bcmbca devices with different changes to yaml, kconfig, > makefile, sub-directory while they actually share many common blocks, > drivers and dts entries. Your commit does not explain why you are doing it at all. We have all this discussion, you put so many arguments, but why none of it is in the commit description? > > While nobody would bind a device to brcm,bcmbca (and it can not be > binded because bcmbca,yaml require to prefix with a specific chip), it > is a great way to make it easy for people to understand what device they > are working and look for the bcmbca common driver and other support code > as well. Wouldn't this be good thing to have? > > And don't forget we introduced bcmbca awhile back with first SoC 47622 > and have set a clear goal for the purpose we are discussing here today: > Please see this patch series: > http://lists.infradead.org/pipermail/linux-arm-kernel/2022-April/732867.html > "This change introduces Broadcom's ARCH_BCMBCA architecture for > armv7 and armv8 based Broadband SoCs. We expect to send additional > patches for each SoC in the near future." > > And Krzysztof acked that yaml for brcm,bcabca here : > http://lists.infradead.org/pipermail/linux-arm-kernel/2022-April/732867.html and I keep discussing, so bringing it up proves what? That new comments appeared? > > Best regards, Krzysztof
On 22/07/2022 02:07, William Zhang wrote: > > > On 07/21/2022 12:01 AM, Krzysztof Kozlowski wrote: >> On 21/07/2022 08:51, Rafał Miłecki wrote: >>> On 2022-07-21 08:44, Krzysztof Kozlowski wrote: >>>> On 21/07/2022 02:06, William Zhang wrote: >>>>> Append "brcm,bcmbca" to BCM4908 chip family compatible strings. Add >>>>> generic 4908 board entry. >>>> >>>> This does not explain at all why you are doing it. Improve your commit >>>> messages. >>> >>> To clarify it from my side (and maybe help a bit): >>> >>> 1. As I understand it BCMBCA is a one big family of SoCs. >>> 2. BCM4908 is a subset of that family (a subfamily?) designed for a >>> specific group of devices. >>> >>> If that's correct I think William it's what you should describe in your >>> commit message. That would make binding more accurate and should be a >>> good argument for your change (I believe). >> >> That's better argument. But what's the benefit of adding generic >> compatible? Devices cannot bind to it (it is too generic). Does it >> describe the device anyhow? Imagine someone adding compatible >> "brcm,all-soc-of-broadcom" - does it make any sense? >> > In case you were also referring the generic 4908 board compatible string > brcm,bcm94908, this is for a bare bone 4908 board dts that only enables No, we refer to the contents of the patch, so bcmbca compatible. I did not see you introducing here bcm4908 compatible. > ARM cpu subsystem, memory and uart. It can be used on all 4908 based > Broadcom reference boards and customer board. It is especially useful > for initial board bring up and one can load this generic board and start > work and debug from the console. Also would be helpful to do a quick > verification of new kernel version when there is cpu subsystem related > change. > > I guess my mindset already assume people are now familiar with this > model of bcmbca binding addition for a new SoC since we introduced the > bcmbca arch with first soc 47622 and 10+ other socs late. But sure I > agree and I will update the commit message with more details in addition > to what the cover letter says. Best regards, Krzysztof
On 07/22/2022 11:22 AM, Krzysztof Kozlowski wrote: > On 21/07/2022 21:35, William Zhang wrote: >> >> >> On 07/21/2022 09:43 AM, Florian Fainelli wrote: >>> On 7/21/22 00:50, Rafał Miłecki wrote: >>>> On 2022-07-21 09:36, Krzysztof Kozlowski wrote: >>>>> On 21/07/2022 09:13, Rafał Miłecki wrote: >>>>>>> That's better argument. But what's the benefit of adding generic >>>>>>> compatible? Devices cannot bind to it (it is too generic). Does it >>>>>>> describe the device anyhow? Imagine someone adding compatible >>>>>>> "brcm,all-soc-of-broadcom" - does it make any sense? >> >> >>>>>> >>>>>> OK, I see it now. I can't think of any case of handling all devices >>>>>> covered with suc a wide brcm,bcmbca binding. >>>>> >>>>> Maybe there is some common part of a SoC which that generic compatible >>>>> would express? >>>>> >>>>> Most archs don't use soc-wide generic compatible, because of reasons I >>>>> mentioned - no actual benefits for anyone from such compatible. >>>>> >>>>> But there are exceptions. I fouun socfpga and apple. The apple sounds as >>>>> mistake to me, because the generic "apple,arm-platform" compatible looks >>>>> like covering all possible Apple ARM platforms. I think Apple ARM >>>>> designs in 20 years will not be compatible at all with current design, >>>>> so such broad compatible is not useful... but that's only my opinion. >>>> >>>> Let's see if William / Broadcom guys can provide a valid argument for >>>> the brcm,bcmbca. >>> >>> It is common practice to provide a generic fallback compatible string for a given chip family/architecture and all of our existing in-tree (and out of tree for that matter) DTSes for Broadcom SoCs do that: >>> >>> - Documentation/devicetree/bindings/arm/bcm/brcm,brcmstb.txt >>> - Documentation/devicetree/bindings/arm/bcm/brcm,ns2.yaml >>> - Documentation/devicetree/bindings/arm/bcm/brcm,nsp.yaml >>> - Documentation/devicetree/bindings/arm/bcm/brcm,cygnus.yaml >>> >>> list goes on and on, of course the counter examples are bcm2835, bcm4708 etc. although those are both chip and families technically, so I suppose the conflation is appropriate in that case. So the pattern is simple: >>> >>> - outside of Broadcom contributors used convention >>> - inside of Broadcom contributors used another >>> >>> so if nothing else, we ought to be consistent within ourselves as Broadcom insiders, which we are doing here. >>> >>> While the generic fallback may not be in use, it still serves a purpose: >>> >>> - Broadcom likes to create a gazillion of part numbers that are hard to untangle from their original SoC architecture unless you happen to work there so it serves as documentation for others to identify what family they belong to, and what to expect from that >>> >>> - you never know when you might want to be matching on just the generic compatible string of a family and putting it in there costs nothing at all >>> >>> The point of William's patch series is to right a number of wrongs on Broadcom's side: >>> >>> - lack of appropriate involvements at the time Rafal submitted the 4908 support as a "standalone" family, I am to take the blame for suggesting that name in the first place, though I did not know at the time that William and others would ever be contributing upstream >>> >>> - avoid the proliferation of "sub" families within a larger family (BCMBCA) since that serves no purpose other than to make it harder on users to select what they should be selecting in their kernel *and* it makes us inconsistent with arch/arm64/Kconfig.platforms that attempts to reduce those >>> >>> I would conclude by asking you: why is this such a big issue? What *actual* problem does it causes, except maybe setting a precedent that you do not like, but for which you practically should have no reason to care as long as the binding is enforced. >>> >> Totally agreed. Just want to emphasize that the main reason of this >> change to merge all the bcmbca family chips into the same group for >> better organization and reduce the clutter to the kernel source. Think >> about 18 bcmbca devices with different changes to yaml, kconfig, >> makefile, sub-directory while they actually share many common blocks, >> drivers and dts entries. > > Your commit does not explain why you are doing it at all. We have all > this discussion, you put so many arguments, but why none of it is in the > commit description? > The purpose of the discussion was to explain to why we think appending brcm,bcmbca is necessary and helpful and the history of this string when we first upstream the bcmbca SoC. And I also said I totally agree to the improvement of commit message. I just posted the v2 of this patch series with all the requests accommodated from this discussion. >> >> While nobody would bind a device to brcm,bcmbca (and it can not be >> binded because bcmbca,yaml require to prefix with a specific chip), it >> is a great way to make it easy for people to understand what device they >> are working and look for the bcmbca common driver and other support code >> as well. Wouldn't this be good thing to have? >> >> And don't forget we introduced bcmbca awhile back with first SoC 47622 >> and have set a clear goal for the purpose we are discussing here today: >> Please see this patch series: >> http://lists.infradead.org/pipermail/linux-arm-kernel/2022-April/732867.html >> "This change introduces Broadcom's ARCH_BCMBCA architecture for >> armv7 and armv8 based Broadband SoCs. We expect to send additional >> patches for each SoC in the near future." >> >> And Krzysztof acked that yaml for brcm,bcabca here : >> http://lists.infradead.org/pipermail/linux-arm-kernel/2022-April/732867.html > > and I keep discussing, so bringing it up proves what? That new comments > appeared? > >> >> > > > Best regards, > Krzysztof >
diff --git a/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml b/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml index 6a64afa95918..4494a2c58c7f 100644 --- a/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml +++ b/Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml @@ -36,18 +36,22 @@ properties: - tplink,archer-c2300-v1 - const: brcm,bcm4906 - const: brcm,bcm4908 + - const: brcm,bcmbca - description: BCM4908 based boards items: - enum: - asus,gt-ac5300 - netgear,raxe500 + - brcm,bcm94908 - const: brcm,bcm4908 + - const: brcm,bcmbca - description: BCM49408 based boards items: - const: brcm,bcm49408 - const: brcm,bcm4908 + - const: brcm,bcmbca - description: BCM4912 based boards items:
Append "brcm,bcmbca" to BCM4908 chip family compatible strings. Add generic 4908 board entry. Signed-off-by: William Zhang <william.zhang@broadcom.com> --- Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml | 4 ++++ 1 file changed, 4 insertions(+)