Re: [PATCH 2/6] drm/i915: Do not wait atomically for display clocks

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 2/6] drm/i915: Do not wait atomically for display clocks
Date: Mon, 1 Feb 2016 18:58:34 +0200	[thread overview]
Message-ID: <20160201165834.GR23290@intel.com> (raw)
In-Reply-To: <1454344071-15881-2-git-send-email-tvrtko.ursulin@linux.intel.com>

On Mon, Feb 01, 2016 at 04:27:47PM +0000, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> 
> Looks like this code does not need to wait atomically since it
> otherwise takes the mutex. But did it rely on on the requested
> 1us wait actually being up to 1ms?

Bspec says 1 us, so it *should* be fine.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 304fc9637026..a7530cf612d7 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -9753,8 +9753,8 @@ static void broadwell_set_cdclk(struct drm_device *dev, int cdclk)
>  	val |= LCPLL_CD_SOURCE_FCLK;
>  	I915_WRITE(LCPLL_CTL, val);
>  
> -	if (wait_for_atomic_us(I915_READ(LCPLL_CTL) &
> -			       LCPLL_CD_SOURCE_FCLK_DONE, 1))
> +	if (wait_for_us(I915_READ(LCPLL_CTL) &
> +			LCPLL_CD_SOURCE_FCLK_DONE, 1))
>  		DRM_ERROR("Switching to FCLK failed\n");
>  
>  	val = I915_READ(LCPLL_CTL);
> @@ -9788,8 +9788,8 @@ static void broadwell_set_cdclk(struct drm_device *dev, int cdclk)
>  	val &= ~LCPLL_CD_SOURCE_FCLK;
>  	I915_WRITE(LCPLL_CTL, val);
>  
> -	if (wait_for_atomic_us((I915_READ(LCPLL_CTL) &
> -				LCPLL_CD_SOURCE_FCLK_DONE) == 0, 1))
> +	if (wait_for_us((I915_READ(LCPLL_CTL) &
> +			LCPLL_CD_SOURCE_FCLK_DONE) == 0, 1))
>  		DRM_ERROR("Switching back to LCPLL failed\n");
>  
>  	mutex_lock(&dev_priv->rps.hw_lock);
> -- 
> 1.9.1

-- 
Ville Syrjälä
Intel OTC
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