Re: [Intel-gfx] [PATCH 7/7] drm/i915/rpm: Enable D3Cold VRAM SR Support

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, May 18, 2022 at 06:37:16PM +0530, Anshuman Gupta wrote:
> Intel Client DGFX card supports D3Cold with two option.
> D3Cold-off zero watt, D3Cold-VRAM Self Refresh.
> 
> i915 requires to evict the lmem objects to smem in order to
> support D3Cold-Off, which increases i915 the suspend/resume
> latency. Enabling VRAM Self Refresh feature optimize the
> latency with additional power cost which required to retain
> the lmem.
> 
> Adding intel_runtime_idle (runtime_idle callback) to enable
> VRAM_SR, it will be used for policy to choose
> between D3Cold-off vs D3Cold-VRAM_SR.
> 
> Since we have introduced i915 runtime_idle callback.
> It need to be warranted that Runtime PM Core invokes runtime_idle
> callback when runtime usages count becomes zero. That requires
> to use pm_runtime_put instead of pm_runtime_put_autosuspend.
> 
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Chris Wilson <chris.p.wilson@intel.com>
> Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_driver.c      | 26 +++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_runtime_pm.c |  3 +--
>  2 files changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
> index 5a9d5529fc90..bbb11c632799 100644
> --- a/drivers/gpu/drm/i915/i915_driver.c
> +++ b/drivers/gpu/drm/i915/i915_driver.c
> @@ -1541,6 +1541,31 @@ static int i915_pm_restore(struct device *kdev)
>  	return i915_pm_resume(kdev);
>  }
>  
> +static int intel_runtime_idle(struct device *kdev)
> +{
> +	struct drm_i915_private *dev_priv = kdev_to_i915(kdev);
> +	int ret = 1;
> +
> +	if (!HAS_LMEM_SR(dev_priv)) {
> +		/*TODO: Prepare for D3Cold-Off */
> +		goto out;
> +	}
> +
> +	disable_rpm_wakeref_asserts(&dev_priv->runtime_pm);
> +
> +	ret = intel_pm_vram_sr(dev_priv, true)

I don't get why this idle callback is here. Why aren't you just
calling that directly from the suspend handler?

> +	if (!ret)
> +		drm_dbg(&dev_priv->drm, "VRAM Self Refresh enabled\n");
> +
> +	enable_rpm_wakeref_asserts(&dev_priv->runtime_pm);
> +
> +out:
> +	pm_runtime_mark_last_busy(kdev);
> +	pm_runtime_autosuspend(kdev);
> +
> +	return ret;
> +}
> +
>  static int intel_runtime_suspend(struct device *kdev)
>  {
>  	struct drm_i915_private *dev_priv = kdev_to_i915(kdev);
> @@ -1726,6 +1751,7 @@ const struct dev_pm_ops i915_pm_ops = {
>  	.restore = i915_pm_restore,
>  
>  	/* S0ix (via runtime suspend) event handlers */
> +	.runtime_idle = intel_runtime_idle,
>  	.runtime_suspend = intel_runtime_suspend,
>  	.runtime_resume = intel_runtime_resume,
>  };
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index 6ed5786bcd29..4dade7e8a795 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -492,8 +492,7 @@ static void __intel_runtime_pm_put(struct intel_runtime_pm *rpm,
>  
>  	intel_runtime_pm_release(rpm, wakelock);
>  
> -	pm_runtime_mark_last_busy(kdev);
> -	pm_runtime_put_autosuspend(kdev);
> +	pm_runtime_put(kdev);
>  }
>  
>  /**
> -- 
> 2.26.2

-- 
Ville Syrjälä
Intel