[Intel-gfx] [PATCH 5/6] drm/i915: add i915.pc8_timeout function

[Rodrigo Vivi]

Reviewed-by: Rodrigo Vivi <rodrigo.vivi at gmail.com>

On Mon, Aug 19, 2013 at 1:18 PM, Paulo Zanoni <przanoni at gmail.com> wrote:
> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
>
> We currently only enter PC8+ after all its required conditions are
> met, there's no rendering, and we stay like that for at least 5
> seconds.
>
> I chose "5 seconds" because this value is conservative and won't make
> us enter/leave PC8+ thousands of times after the screen is off: some
> desktop environments have applications that wake up and do rendering
> every 1-3 seconds, even when the screen is off and the machine is
> completely idle.
>
> But when I was testing my PC8+ patches I set the default value to
> 100ms so I could use the bad-behaving desktop environments to
> stress-test my patches. I also thought it would be a good idea to ask
> our power management team to test different values, but I'm pretty
> sure they would ask me for an easy way to change the timeout. So to
> help these 2 cases I decided to create an option that would make it
> easier to change the default value. I also expect people making
> specific products that use our driver could try to find the perfect
> timeout for them.
>
> Anyway, fixing the bad-behaving applications will always lead to
> better power savings than just changing the timeout value: you need to
> stop waking the Kernel, not quickly put it back to sleep again after
> you wake it for nothing. Bad sleep leads to bad mood!
>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.c      | 4 ++++
>  drivers/gpu/drm/i915/i915_drv.h      | 1 +
>  drivers/gpu/drm/i915/intel_display.c | 2 +-
>  3 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index f197362..ad28a72 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -145,6 +145,10 @@ int i915_enable_pc8 __read_mostly = 0;
>  module_param_named(enable_pc8, i915_enable_pc8, int, 0600);
>  MODULE_PARM_DESC(enable_pc8, "Enable support for low power package C states (PC8+) (default: false)");
>
> +int i915_pc8_timeout __read_mostly = 5000;
> +module_param_named(pc8_timeout, i915_pc8_timeout, int, 0600);
> +MODULE_PARM_DESC(pc8_timeout, "Number of msecs of idleness required to enter PC8+ (default: 5000)");
> +
>  bool i915_prefault_disable __read_mostly;
>  module_param_named(prefault_disable, i915_prefault_disable, bool, 0600);
>  MODULE_PARM_DESC(prefault_disable,
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 34c5af5..3138083 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1710,6 +1710,7 @@ extern int i915_disable_power_well __read_mostly;
>  extern int i915_enable_ips __read_mostly;
>  extern bool i915_fastboot __read_mostly;
>  extern int i915_enable_pc8 __read_mostly;
> +extern int i915_pc8_timeout __read_mostly;
>  extern bool i915_prefault_disable __read_mostly;
>
>  extern int i915_suspend(struct drm_device *dev, pm_message_t state);
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 7d5b01a..ba3bdd5 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -6099,7 +6099,7 @@ static void __hsw_enable_package_c8(struct drm_i915_private *dev_priv)
>                 return;
>
>         schedule_delayed_work(&dev_priv->pc8.enable_work,
> -                             msecs_to_jiffies(5 * 1000));
> +                             msecs_to_jiffies(i915_pc8_timeout));
>  }
>
>  static void __hsw_disable_package_c8(struct drm_i915_private *dev_priv)
> --
> 1.8.1.2
>
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-- 
Rodrigo Vivi
Blog: http://blog.vivi.eng.br