Re: [PATCH] drm/i915: Wait old forcewake ack to clear on vlv

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Ville Syrjälä <ville.syrjala@linux.intel.com> writes:

> On Wed, Nov 05, 2014 at 10:18:46AM +0200, Mika Kuoppala wrote:
>> Don't rush into getting new fw until the clearing
>> of old one has been acked.
>> 
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=85684
>> Tested-by: lu hua <huax.lu@intel.com>
>> Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
>
> This is just a revert of 
>  commit 5cb13c07dae73380d8b3ddc792740487b8742938
>  Author: Deepak S <deepak.s@linux.intel.com>
>  Date:   Thu Sep 18 18:51:50 2014 +0530
>
>     drm/i915/vlv: Remove check for Old Ack during forcewake
>
> except you left the comment behind.

I failed at archeology. There is even nice comment from Deepak on
top I managed to miss.

But after reading this comment and the workaround description, I
think that this WaRsDontPollForAckOnClearingFWBits is not valid for
our use case.

We use only one bit per engine, so our use case is not multithreaded
in that sense.

-Mika

> Would be nice to have some kind of real explanation what is going on
> here. Deepak, any ideas?
>
>> ---
>>  drivers/gpu/drm/i915/intel_uncore.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
>> index 9427641..5259b38 100644
>> --- a/drivers/gpu/drm/i915/intel_uncore.c
>> +++ b/drivers/gpu/drm/i915/intel_uncore.c
>> @@ -204,6 +204,10 @@ 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: waiting for old Render ack to clear.\n");
>> +
>>  		__raw_i915_write32(dev_priv, FORCEWAKE_VLV,
>>  				   _MASKED_BIT_ENABLE(FORCEWAKE_KERNEL));
>>  
>> @@ -217,6 +221,11 @@ 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: waiting for old media ack to clear.\n");
>> +
>> +
>>  		__raw_i915_write32(dev_priv, FORCEWAKE_MEDIA_VLV,
>>  				   _MASKED_BIT_ENABLE(FORCEWAKE_KERNEL));
>>  
>> -- 
>> 1.9.1
>> 
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> -- 
> Ville Syrjälä
> Intel OTC
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