Re: [PATCH V5 18/20] ARM: exynos: cpuidle: Pass the AFTR callback to the platform_data

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On 05/09/2014 02:02 PM, Tomasz Figa wrote:
Hi Arnd,

On 09.05.2014 12:56, Arnd Bergmann wrote:
On Friday 11 April 2014, Daniel Lezcano wrote:
No more dependency on the arch code. The platform_data field is used to set the
PM callback as the other cpuidle drivers.

Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Reviewed-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx>

This has just shown up in linux-next and broken randconfig builds.

diff --git a/arch/arm/mach-exynos/exynos.c b/arch/arm/mach-exynos/exynos.c
index fe8dac8..d22f0e4 100644
--- a/arch/arm/mach-exynos/exynos.c
+++ b/arch/arm/mach-exynos/exynos.c
@@ -221,8 +221,9 @@ void exynos_restart(enum reboot_mode mode, const char *cmd)
  }

  static struct platform_device exynos_cpuidle = {
-       .name           = "exynos_cpuidle",
-       .id             = -1,
+       .name              = "exynos_cpuidle",
+       .dev.platform_data = exynos_enter_aftr,
+       .id                = -1,
  };


This is wrong on many levels, can we please do this properly?

* The exynos_enter_aftr function is compiled conditionally, so you can't just
   reference it from generic code, or you get a link error.

+1

That is true but still we have a link error without this patch. We shouldn't register and declare this structure if CONFIG_PM / CONFIG_CPU_IDLE are not set.

* 'static struct platform_device ...' has been deprecated for at least a decade,
   stop doing that. For any platform devices that get registered, there is
   platform_device_register_simple().

+0.5

The missing 0.5 is because you can't pass platform data using
platform_device_register_simple(). There is
platform_device_register_resndata(), though.

* There shouldn't need to be a platform_device to start with, this should all
   come from DT. We can't do this on arm64 anyway, so any code that may be
   shared between arm32 and arm64 should have proper abstractions.

-1

Exynos cpuidle is not a device on the SoC, so I don't think there is any
way to represent it in DT. The only thing I could see this is matching
root node with a central SoC driver that instantiates specific
subdevices, such as cpufreq and cpuidle, but I don't see any available
infrastructure for this.

There is a RFC for defining generic idle states [1].

The idea behind using the platform driver framework is to unify the code across the different drivers and separate the PM / cpuidle code.

By this way, we can move the different drivers to drivers/cpuidle and store them in a single place. That make easier the tracking, the review and the maintenance.

I am ok to by using platform_device_register_resndata() but I would prefer to do that a bit later by converting the other drivers too. That will be easier if we have them grouped in a single directory (this is what does this patchset at the end).

As there are some more work based on this patchset and the link error could be fixed as an independent patch, I would recommend to re-integrate it in the tree as asked by Bartlomiej.

Thanks
  -- Daniel


[1] http://www.spinics.net/lists/arm-kernel/msg328747.html


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