Re: [PATCH] drm/i915/vlv: Remove check for Old Ack during forcewake

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

On Thu, Sep 18, 2014 at 06:51:50PM +0530, deepak.s@linux.intel.com wrote:
> From: Deepak S <deepak.s@linux.intel.com>
> 
> Based on the HW team inputs. We can should not wait for the old ack,
> Waiting for old ack might fail, when other forcewake came before the
> present one is desserted.
> 
> for example, if forcewake bit 0 was set and before it could get cleared
> forcewake bit 1 got set, HW eventually clear bit 0, when the bit 1
> is cleared. i.e, bit 1 is still sent then forcewake bit 0 will still be
> set.
> 
> Signed-off-by: Deepak S <deepak.s@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_uncore.c | 10 ----------
>  1 file changed, 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index 918b761..bcb0806 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -196,11 +196,6 @@ static void __vlv_force_wake_get(struct drm_i915_private *dev_priv,
>  {
>  	/* Check for Render Engine */
>  	if (FORCEWAKE_RENDER & fw_engine) {
> -		if (wait_for_atomic((__raw_i915_read32(dev_priv,
> -						FORCEWAKE_ACK_VLV) &
> -						FORCEWAKE_KERNEL) == 0,
> -					FORCEWAKE_ACK_TIMEOUT_MS))
> -			DRM_ERROR("Timed out: Render forcewake old ack to clear.\n");
>  

Can we have a comment here? Something like this perhaps:

/*
 * WaRsDontPollForAckOnClearingFWBits:vlv
 * Hardware clears ack bits lazily (only when all ack
 * bits become 0) so don't poll for individiual ack
 * bits to be clear here.
 */

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

>  		__raw_i915_write32(dev_priv, FORCEWAKE_VLV,
>  				   _MASKED_BIT_ENABLE(FORCEWAKE_KERNEL));
> @@ -214,11 +209,6 @@ static void __vlv_force_wake_get(struct drm_i915_private *dev_priv,
>  
>  	/* Check for Media Engine */
>  	if (FORCEWAKE_MEDIA & fw_engine) {
> -		if (wait_for_atomic((__raw_i915_read32(dev_priv,
> -						FORCEWAKE_ACK_MEDIA_VLV) &
> -						FORCEWAKE_KERNEL) == 0,
> -					FORCEWAKE_ACK_TIMEOUT_MS))
> -			DRM_ERROR("Timed out: Media forcewake old ack to clear.\n");
>  
>  		__raw_i915_write32(dev_priv, FORCEWAKE_MEDIA_VLV,
>  				   _MASKED_BIT_ENABLE(FORCEWAKE_KERNEL));
> -- 
> 1.9.1
> 
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-- 
Ville Syrjälä
Intel OTC