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

[Deepak S <deepak.s@intel.com>]

On Thursday 18 September 2014 02:09 PM, Ville Syrjälä wrote:
> 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>

Thanks Ville, I will change the commit message.

>>   		__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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