Re: [PATCH 2/2] drm/i915: Only enabled DRRS if PRS won't be enabled on this pipe.

[Ramalingam C <ramalingam.c@intel.com>]

On Wednesday 25 March 2015 09:11 PM, Vivi, Rodrigo wrote:
> On Wed, 2015-03-25 at 16:08 +0530, Ramalingam C wrote:
>> On Wednesday 25 March 2015 12:42 AM, Rodrigo Vivi wrote:
>>> With PSR enabled being pre computed on pipe_config we can now
>>> prevent DRRS to be enabled along with PSR.
>>>
>>> Cc: Ramalingam C <ramalingam.c@intel.com>
>>> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
>>> ---
>>>    drivers/gpu/drm/i915/intel_dp.c | 10 +++++-----
>>>    1 file changed, 5 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>>> index 637dd53..af28833 100644
>>> --- a/drivers/gpu/drm/i915/intel_dp.c
>>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>>> @@ -4992,11 +4992,6 @@ static void intel_dp_set_drrs_state(struct drm_device *dev, int refresh_rate)
>>>    		return;
>>>    	}
>>>    
>>> -	/*
>>> -	 * FIXME: This needs proper synchronization with psr state for some
>>> -	 * platforms that cannot have PSR and DRRS enabled at the same time.
>>> -	 */
>>> -
>>>    	dig_port = dp_to_dig_port(intel_dp);
>>>    	encoder = &dig_port->base;
>>>    	intel_crtc = encoder->new_crtc;
>>> @@ -5082,6 +5077,11 @@ void intel_edp_drrs_enable(struct intel_dp *intel_dp)
>>>    		return;
>>>    	}
>>>    
>>> +	if (intel_crtc->config->psr_enabled) {
>>> +		DRM_DEBUG_KMS("DRRS: PSR enabled on this crtc\n");
>>> +		return;
>>> +	}
>>> +
>> But you might want to explicitly disable the DRRS when PSR is supported.
>> Because incase DRRS is enabled before PSR,
>> then blocking the enable call wont help us to stop DRRS.
>> In fact I would have suggested to place this in DRRS init path.  But a
>> feature called media playback DRRS(in RFC stage)
>> needs DRRS active even when PSR is enabled/supported. So dont want to
>> block the DRRS init path because PSR is supported.
>> Disabling alone will be sufficient.
>>
>> So as soon as PSR support is detected you would like to explicitly
>> disable the DRRS(if it is supported)
>> along with blocking further drrs_enable calls.
> Not actually. Please take a look on the other patch on this series.
> If possible please review both.
>
> intel_crtc->config->psr_enabled is pre-computed and comes before DRRS
> enabling. So with this pre-computed psr enable flag we don't need to
> switch other states because DRRS won't be enabled never.

Thanks for the explanation. Gone through the previous patch in this 
series. As this flag psr_enabled is
getting computed well before the PSR and DRRS enable, then this patch 
will be sufficient to
disable the DRRS.

>
>>>    	mutex_lock(&dev_priv->drrs.mutex);
>>>    	if (WARN_ON(dev_priv->drrs.dp)) {
>>>    		DRM_ERROR("DRRS already enabled\n");

Thanks,
--Ram

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