diff mbox

PM / Domains: Restrict "samsung,power-domain" checks to ARCH_EXYNOS

Message ID 1477049656-27535-1-git-send-email-geert+renesas@glider.be (mailing list archive)
State Rejected, archived
Headers show

Commit Message

Geert Uytterhoeven Oct. 21, 2016, 11:34 a.m. UTC
Currently the generic PM Domain code code checks for the presence of
both (generic) "power-domains" and (Samsung Exynos legacy)
"samsung,power-domain" properties in all device tree nodes representing
devices.

There are two issues with this:
  1. This imposes a small boot-time penalty on all platforms using DT,
  2. Platform-specific checks do not really belong in core framework
     code.

While moving the check from platform-agnostic code to Samsung-specific
code is non-trivial, the runtime overhead can be restricted to kernels
including support for 32-bit Samsung Exynos platforms.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
"samsung,power-domain" was only ever used in:
  - arch/arm/boot/dts/exynos4415.dtsi: Unused?
  - arch/arm/boot/dts/exynos3250.dtsi: CONFIG_ARCH_EXYNOS3
  - arch/arm/boot/dts/exynos4.dtsi:    CONFIG_ARCH_EXYNOS4
  - arch/arm/boot/dts/exynos4x12.dtsi: CONFIG_ARCH_EXYNOS4
				       exynos4212.dtsi is unused?
  - arch/arm/boot/dts/exynos5250.dtsi: CONFIG_ARCH_EXYNOS5
  - arch/arm/boot/dts/exynos5420.dtsi: CONFIG_ARCH_EXYNOS5
---
 drivers/base/power/domain.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Rafael J. Wysocki Oct. 21, 2016, 12:29 p.m. UTC | #1
On Fri, Oct 21, 2016 at 1:34 PM, Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
> Currently the generic PM Domain code code checks for the presence of
> both (generic) "power-domains" and (Samsung Exynos legacy)
> "samsung,power-domain" properties in all device tree nodes representing
> devices.
>
> There are two issues with this:
>   1. This imposes a small boot-time penalty on all platforms using DT,
>   2. Platform-specific checks do not really belong in core framework
>      code.
>
> While moving the check from platform-agnostic code to Samsung-specific
> code is non-trivial, the runtime overhead can be restricted to kernels
> including support for 32-bit Samsung Exynos platforms.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> "samsung,power-domain" was only ever used in:
>   - arch/arm/boot/dts/exynos4415.dtsi: Unused?
>   - arch/arm/boot/dts/exynos3250.dtsi: CONFIG_ARCH_EXYNOS3
>   - arch/arm/boot/dts/exynos4.dtsi:    CONFIG_ARCH_EXYNOS4
>   - arch/arm/boot/dts/exynos4x12.dtsi: CONFIG_ARCH_EXYNOS4
>                                        exynos4212.dtsi is unused?
>   - arch/arm/boot/dts/exynos5250.dtsi: CONFIG_ARCH_EXYNOS5
>   - arch/arm/boot/dts/exynos5420.dtsi: CONFIG_ARCH_EXYNOS5
> ---
>  drivers/base/power/domain.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index e023066e421547c5..d94d6a4b9b527108 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -1853,7 +1853,8 @@ int genpd_dev_pm_attach(struct device *dev)
>         ret = of_parse_phandle_with_args(dev->of_node, "power-domains",
>                                         "#power-domain-cells", 0, &pd_args);
>         if (ret < 0) {
> -               if (ret != -ENOENT)
> +               if (ret != -ENOENT || !IS_ENABLED(CONFIG_ARCH_EXYNOS) ||

Please don't check things like CONFIG_ARCH_EXYNOS in the core.

If you need to put checks like that here, there is a design problem somewhere.

And imagine someone 5 years ahead from now looking at this code and
wondering why on Earth the check is here.

> +                   IS_ENABLED(CONFIG_64BIT))
>                         return ret;
>
>                 /*
> --

Thanks,
Rafael
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Krzysztof Kozlowski Oct. 21, 2016, 1:58 p.m. UTC | #2
On Fri, Oct 21, 2016 at 02:29:05PM +0200, Rafael J. Wysocki wrote:
> On Fri, Oct 21, 2016 at 1:34 PM, Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
> > Currently the generic PM Domain code code checks for the presence of
> > both (generic) "power-domains" and (Samsung Exynos legacy)
> > "samsung,power-domain" properties in all device tree nodes representing
> > devices.
> >
> > There are two issues with this:
> >   1. This imposes a small boot-time penalty on all platforms using DT,
> >   2. Platform-specific checks do not really belong in core framework
> >      code.
> >
> > While moving the check from platform-agnostic code to Samsung-specific
> > code is non-trivial, the runtime overhead can be restricted to kernels
> > including support for 32-bit Samsung Exynos platforms.
> >
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > ---
> > "samsung,power-domain" was only ever used in:
> >   - arch/arm/boot/dts/exynos4415.dtsi: Unused?
> >   - arch/arm/boot/dts/exynos3250.dtsi: CONFIG_ARCH_EXYNOS3
> >   - arch/arm/boot/dts/exynos4.dtsi:    CONFIG_ARCH_EXYNOS4
> >   - arch/arm/boot/dts/exynos4x12.dtsi: CONFIG_ARCH_EXYNOS4
> >                                        exynos4212.dtsi is unused?
> >   - arch/arm/boot/dts/exynos5250.dtsi: CONFIG_ARCH_EXYNOS5
> >   - arch/arm/boot/dts/exynos5420.dtsi: CONFIG_ARCH_EXYNOS5
> > ---
> >  drivers/base/power/domain.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index e023066e421547c5..d94d6a4b9b527108 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -1853,7 +1853,8 @@ int genpd_dev_pm_attach(struct device *dev)
> >         ret = of_parse_phandle_with_args(dev->of_node, "power-domains",
> >                                         "#power-domain-cells", 0, &pd_args);
> >         if (ret < 0) {
> > -               if (ret != -ENOENT)
> > +               if (ret != -ENOENT || !IS_ENABLED(CONFIG_ARCH_EXYNOS) ||
> 
> Please don't check things like CONFIG_ARCH_EXYNOS in the core.
> 
> If you need to put checks like that here, there is a design problem somewhere.
> 
> And imagine someone 5 years ahead from now looking at this code and
> wondering why on Earth the check is here.

I don't find the argument of performance penalty such important but for
the sake of design, the samsung-specific code could be moved to
drivers/soc/samsung/pm_domains.c, called "legacy_pm_parse" and exported
through a header. Thus with !ARCH_EXYNOS that would be 'static inline
{}'.  However that is not a nice solution - there will be still
direct call to platform-specific code in the core. I am not sure if it
is worth the effort.

The samsung,power-domain was made deprecated (although not explicitly)
in January 2015 (0da658704136 ("ARM: dts: convert to generic power
domain bindings for exynos DT")) so how about:
1. Printing a dev_warn() about usage of deprecated bindings.
2. Complete removal in January 2017?

Best regards,
Krzysztof
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Krzysztof Kozlowski Oct. 21, 2016, 2:06 p.m. UTC | #3
On Fri, Oct 21, 2016 at 02:29:05PM +0200, Rafael J. Wysocki wrote:
> On Fri, Oct 21, 2016 at 1:34 PM, Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
> > Currently the generic PM Domain code code checks for the presence of
> > both (generic) "power-domains" and (Samsung Exynos legacy)
> > "samsung,power-domain" properties in all device tree nodes representing
> > devices.
> >
> > There are two issues with this:
> >   1. This imposes a small boot-time penalty on all platforms using DT,
> >   2. Platform-specific checks do not really belong in core framework
> >      code.
> >
> > While moving the check from platform-agnostic code to Samsung-specific
> > code is non-trivial, the runtime overhead can be restricted to kernels
> > including support for 32-bit Samsung Exynos platforms.
> >
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > ---
> > "samsung,power-domain" was only ever used in:
> >   - arch/arm/boot/dts/exynos4415.dtsi: Unused?
> >   - arch/arm/boot/dts/exynos3250.dtsi: CONFIG_ARCH_EXYNOS3
> >   - arch/arm/boot/dts/exynos4.dtsi:    CONFIG_ARCH_EXYNOS4
> >   - arch/arm/boot/dts/exynos4x12.dtsi: CONFIG_ARCH_EXYNOS4
> >                                        exynos4212.dtsi is unused?
> >   - arch/arm/boot/dts/exynos5250.dtsi: CONFIG_ARCH_EXYNOS5
> >   - arch/arm/boot/dts/exynos5420.dtsi: CONFIG_ARCH_EXYNOS5
> > ---
> >  drivers/base/power/domain.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index e023066e421547c5..d94d6a4b9b527108 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -1853,7 +1853,8 @@ int genpd_dev_pm_attach(struct device *dev)
> >         ret = of_parse_phandle_with_args(dev->of_node, "power-domains",
> >                                         "#power-domain-cells", 0, &pd_args);
> >         if (ret < 0) {
> > -               if (ret != -ENOENT)
> > +               if (ret != -ENOENT || !IS_ENABLED(CONFIG_ARCH_EXYNOS) ||
> 
> Please don't check things like CONFIG_ARCH_EXYNOS in the core.
> 
> If you need to put checks like that here, there is a design problem somewhere.
> 
> And imagine someone 5 years ahead from now looking at this code and
> wondering why on Earth the check is here.

Sorry for the noise, sending once again without bogus recipient added by
mistake:

I don't find the argument of performance penalty such important but for
the sake of design, the samsung-specific code could be moved to
drivers/soc/samsung/pm_domains.c, called "legacy_pm_parse" and exported
through a header. Thus with !ARCH_EXYNOS that would be 'static inline
{}'.  However that is not a nice solution - there will be still
direct call to platform-specific code in the core. I am not sure if it
is worth the effort.

The samsung,power-domain was made deprecated (although not explicitly)
in January 2015 (0da658704136 ("ARM: dts: convert to generic power
domain bindings for exynos DT")) so how about:
1. Printing a dev_warn() about usage of deprecated bindings.
2. Complete removal in January 2017?

Best regards,
Krzysztof
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On 10/21/2016 03:58 PM, Krzysztof Kozlowski wrote:
> The samsung,power-domain was made deprecated (although not explicitly)
> in January 2015 (0da658704136 ("ARM: dts: convert to generic power
> domain bindings for exynos DT")) so how about:
> 1. Printing a dev_warn() about usage of deprecated bindings.
> 2. Complete removal in January 2017?

I doubt anyone will ever use new mainline kernel with older dts/dtb
so IMHO it makes sense to queue a patch removing support for the
deprecated compatible just now and don't bother with a warning.

Documentation/devicetree/bindings/display/exynos/exynos7-decon.txt
arch/arm/boot/dts/exynos4415.dtsi
would just need to be updated in same release, I can prepare a patch
for these files.

--
Thanks,
Sylwester
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Javier Martinez Canillas Oct. 21, 2016, 2:18 p.m. UTC | #5
Hello Sylwester,

On 10/21/2016 11:14 AM, Sylwester Nawrocki wrote:
> On 10/21/2016 03:58 PM, Krzysztof Kozlowski wrote:
>> The samsung,power-domain was made deprecated (although not explicitly)
>> in January 2015 (0da658704136 ("ARM: dts: convert to generic power
>> domain bindings for exynos DT")) so how about:
>> 1. Printing a dev_warn() about usage of deprecated bindings.
>> 2. Complete removal in January 2017?
> 
> I doubt anyone will ever use new mainline kernel with older dts/dtb
> so IMHO it makes sense to queue a patch removing support for the
> deprecated compatible just now and don't bother with a warning.
> 

FWIW I agree with you. I don't know of any Exynos machine that ships a DT
as read-only. Even consumer devices like the Exynos Chromebooks use a FIT
image (kernel + FDT bundled), so the DT can always be updated.

Removing the support for the deprecated property sound sensible to me.

Best regards,
Geert Uytterhoeven Oct. 21, 2016, 2:39 p.m. UTC | #6
Hi Javier,

On Fri, Oct 21, 2016 at 4:18 PM, Javier Martinez Canillas
<javier@osg.samsung.com> wrote:
> On 10/21/2016 11:14 AM, Sylwester Nawrocki wrote:
>> On 10/21/2016 03:58 PM, Krzysztof Kozlowski wrote:
>>> The samsung,power-domain was made deprecated (although not explicitly)
>>> in January 2015 (0da658704136 ("ARM: dts: convert to generic power
>>> domain bindings for exynos DT")) so how about:
>>> 1. Printing a dev_warn() about usage of deprecated bindings.
>>> 2. Complete removal in January 2017?
>>
>> I doubt anyone will ever use new mainline kernel with older dts/dtb
>> so IMHO it makes sense to queue a patch removing support for the
>> deprecated compatible just now and don't bother with a warning.
>>
>
> FWIW I agree with you. I don't know of any Exynos machine that ships a DT
> as read-only. Even consumer devices like the Exynos Chromebooks use a FIT
> image (kernel + FDT bundled), so the DT can always be updated.
>
> Removing the support for the deprecated property sound sensible to me.

I'm happy to hear that!

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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diff mbox

Patch

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index e023066e421547c5..d94d6a4b9b527108 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1853,7 +1853,8 @@  int genpd_dev_pm_attach(struct device *dev)
 	ret = of_parse_phandle_with_args(dev->of_node, "power-domains",
 					"#power-domain-cells", 0, &pd_args);
 	if (ret < 0) {
-		if (ret != -ENOENT)
+		if (ret != -ENOENT || !IS_ENABLED(CONFIG_ARCH_EXYNOS) ||
+		    IS_ENABLED(CONFIG_64BIT))
 			return ret;
 
 		/*