| Message ID | 1421338359-27467-5-git-send-email-tomeu.vizoso@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 01/15/2015 09:12 AM, Tomeu Vizoso wrote: > To silence a warning on Nyan boards. > > Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com> > --- > arch/arm/boot/dts/tegra124-nyan-big.dts | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts b/arch/arm/boot/dts/tegra124-nyan-big.dts > index 9a9cffe..94c7ba9 100644 > --- a/arch/arm/boot/dts/tegra124-nyan-big.dts > +++ b/arch/arm/boot/dts/tegra124-nyan-big.dts > @@ -1660,6 +1660,7 @@ > > flash@0 { > compatible = "winbond,w25q32dw"; > + spi-max-frequency = <25000000>; This property already exists in the SPI controller. Isn't the max frequency supposed to inherit from there? If so, shouldn't the code not warn when such inheritance happens, i.e. it'd be better to fix the code?
On 15 January 2015 at 18:26, Stephen Warren <swarren@wwwdotorg.org> wrote: > On 01/15/2015 09:12 AM, Tomeu Vizoso wrote: >> >> To silence a warning on Nyan boards. >> >> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com> >> --- >> arch/arm/boot/dts/tegra124-nyan-big.dts | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts >> b/arch/arm/boot/dts/tegra124-nyan-big.dts >> index 9a9cffe..94c7ba9 100644 >> --- a/arch/arm/boot/dts/tegra124-nyan-big.dts >> +++ b/arch/arm/boot/dts/tegra124-nyan-big.dts >> @@ -1660,6 +1660,7 @@ >> >> flash@0 { >> compatible = "winbond,w25q32dw"; >> + spi-max-frequency = <25000000>; > > > This property already exists in the SPI controller. Isn't the max frequency > supposed to inherit from there? If so, shouldn't the code not warn when such > inheritance happens, i.e. it'd be better to fix the code? I don't think it's supposed to fall back to the controller's max freq, as each device has its own maximum frequency that it can support and it's not related to what the master supports. Regards, Tomeu
On 01/27/2015 04:13 AM, Tomeu Vizoso wrote: > On 15 January 2015 at 18:26, Stephen Warren <swarren@wwwdotorg.org> wrote: >> On 01/15/2015 09:12 AM, Tomeu Vizoso wrote: >>> >>> To silence a warning on Nyan boards. >>> >>> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com> >>> --- >>> arch/arm/boot/dts/tegra124-nyan-big.dts | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts >>> b/arch/arm/boot/dts/tegra124-nyan-big.dts >>> index 9a9cffe..94c7ba9 100644 >>> --- a/arch/arm/boot/dts/tegra124-nyan-big.dts >>> +++ b/arch/arm/boot/dts/tegra124-nyan-big.dts >>> @@ -1660,6 +1660,7 @@ >>> >>> flash@0 { >>> compatible = "winbond,w25q32dw"; >>> + spi-max-frequency = <25000000>; >> >> >> This property already exists in the SPI controller. Isn't the max frequency >> supposed to inherit from there? If so, shouldn't the code not warn when such >> inheritance happens, i.e. it'd be better to fix the code? > > I don't think it's supposed to fall back to the controller's max freq, > as each device has its own maximum frequency that it can support and > it's not related to what the master supports. If the controller-specific frequency property isn't ever used, we should remove it. No point carrying cruft that looks like it does something but doesn't. Logically, each device's max frequency certainly should be influenced by all of the controller, board, and device max frequency. Those should all impose a cap on the speed used. I'd expect this to be expressed in DT as a single property in each device where the user has calculated that max for the device, with the option to have all the devices fall back to the "default" provided at the controller/bus level if the device imposes a cap that's no lower.
On 27 January 2015 at 17:48, Stephen Warren <swarren@wwwdotorg.org> wrote: > On 01/27/2015 04:13 AM, Tomeu Vizoso wrote: >> >> On 15 January 2015 at 18:26, Stephen Warren <swarren@wwwdotorg.org> wrote: >>> >>> On 01/15/2015 09:12 AM, Tomeu Vizoso wrote: >>>> >>>> >>>> To silence a warning on Nyan boards. >>>> >>>> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com> >>>> --- >>>> arch/arm/boot/dts/tegra124-nyan-big.dts | 1 + >>>> 1 file changed, 1 insertion(+) >>>> >>>> diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts >>>> b/arch/arm/boot/dts/tegra124-nyan-big.dts >>>> index 9a9cffe..94c7ba9 100644 >>>> --- a/arch/arm/boot/dts/tegra124-nyan-big.dts >>>> +++ b/arch/arm/boot/dts/tegra124-nyan-big.dts >>>> @@ -1660,6 +1660,7 @@ >>>> >>>> flash@0 { >>>> compatible = "winbond,w25q32dw"; >>>> + spi-max-frequency = <25000000>; >>> >>> >>> >>> This property already exists in the SPI controller. Isn't the max >>> frequency >>> supposed to inherit from there? If so, shouldn't the code not warn when >>> such >>> inheritance happens, i.e. it'd be better to fix the code? >> >> >> I don't think it's supposed to fall back to the controller's max freq, >> as each device has its own maximum frequency that it can support and >> it's not related to what the master supports. > > > If the controller-specific frequency property isn't ever used, we should > remove it. No point carrying cruft that looks like it does something but > doesn't. > > Logically, each device's max frequency certainly should be influenced by all > of the controller, board, and device max frequency. Those should all impose > a cap on the speed used. I'd expect this to be expressed in DT as a single > property in each device where the user has calculated that max for the > device, with the option to have all the devices fall back to the "default" > provided at the controller/bus level if the device imposes a cap that's no > lower. My understanding is that each device node needs to specify the maximum frequency it supports, and the same for each controller. When configuring the transfer parameters, its frequency will be capped by both the device and controller maximum frequencies. So we currently need to specify the maximum frequencies in both device and controller nodes, and it sounds like a good idea to me. I'm probably missing your point. Is it that it should be possible for device nodes to leave unspecified their max frequency and that in that case the one for the controller should be used instead? Regards, Tomeu
diff --git a/arch/arm/boot/dts/tegra124-nyan-big.dts b/arch/arm/boot/dts/tegra124-nyan-big.dts index 9a9cffe..94c7ba9 100644 --- a/arch/arm/boot/dts/tegra124-nyan-big.dts +++ b/arch/arm/boot/dts/tegra124-nyan-big.dts @@ -1660,6 +1660,7 @@ flash@0 { compatible = "winbond,w25q32dw"; + spi-max-frequency = <25000000>; reg = <0>; }; };
To silence a warning on Nyan boards. Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com> --- arch/arm/boot/dts/tegra124-nyan-big.dts | 1 + 1 file changed, 1 insertion(+)