[Intel-gfx] [PATCH v2] drm/i915: Disable DRRS when PSR is enabled

[Pandiyan, Dhinakaran]

On Thu, 2017-08-31 at 14:17 -0700, Radhakrishna Sripada wrote:
> Some platforms donot support PSR and DRRS simultaneously.

I could not verify which platforms support PSR + DRRS and which don't.
But, seems safe to have DRRS disabled for all platforms when PSR is
enabled.



> Visual artifacts and flickering were reported on BDW HP Spectre
> x360 Convertible. Deferring to PSR when both PSR and DRRS are
> supported by the panel.
> 
> V2: Minor code-style changes suggested by Rodrigo
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101111
> Cc: Nicholas Stommel <nicholas.stommel at gmail.com>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Cc: Clinton Taylor <clinton.a.taylor at intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada at 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 887953c0f495..aa5a69301257 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5467,11 +5467,6 @@ static void intel_dp_set_drrs_state(struct drm_i915_private *dev_priv,
>  		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 = to_intel_crtc(encoder->base.crtc);
> @@ -5555,6 +5550,11 @@ void intel_edp_drrs_enable(struct intel_dp *intel_dp,
>  		return;
>  	}
>  
> +	if (dev_priv->psr.enabled) {
> +		DRM_DEBUG_KMS("PSR enabled. Disabling DRRS.\n");
> +		return;
> +	}

So every time a flush/invalidate happens, we end up taking the
drrs.mutex and then returning because dev_priv->drrs.dp is NULL. That
seems unnecessary. Have your considered drrs.type = DRRS_NOT_SUPPORTED?


And this solution relies on the ordering that psr_enable() is done
before drrs_enable(), we need a comment in enable_ddi to make a note of
that. A WARN_ON in psr_enable() if drrs is already enabled might work
too.


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