Re: [PATCH] drm/i915/psr: Force manual PSR exit in older gens

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Mon, Jun 17, 2019 at 12:51:54PM -0700, José Roberto de Souza wrote:
> To do frontbuffer tracking we are depending on Display WA #0884 to
> exit PSR when there is a frontbuffer modification but according to
> user reports a write to CURSURFLIVE do not cause PSR to exit in older
> gens so lets force a PSR exit.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110799

:(

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

and if bugs persist or this brings back older bugs it is time
to consider removing psr support at all for gen < 9  :-/

> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_psr.c | 36 +++++++++++++++++-------
>  1 file changed, 26 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index 69709df4a648..69d908e6a050 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -863,16 +863,23 @@ void intel_psr_disable(struct intel_dp *intel_dp,
>  
>  static void psr_force_hw_tracking_exit(struct drm_i915_private *dev_priv)
>  {
> -	/*
> -	 * Display WA #0884: all
> -	 * This documented WA for bxt can be safely applied
> -	 * broadly so we can force HW tracking to exit PSR
> -	 * instead of disabling and re-enabling.
> -	 * Workaround tells us to write 0 to CUR_SURFLIVE_A,
> -	 * but it makes more sense write to the current active
> -	 * pipe.
> -	 */
> -	I915_WRITE(CURSURFLIVE(dev_priv->psr.pipe), 0);
> +	if (INTEL_GEN(dev_priv) >= 9)
> +		/*
> +		 * Display WA #0884: skl+
> +		 * This documented WA for bxt can be safely applied
> +		 * broadly so we can force HW tracking to exit PSR
> +		 * instead of disabling and re-enabling.
> +		 * Workaround tells us to write 0 to CUR_SURFLIVE_A,
> +		 * but it makes more sense write to the current active
> +		 * pipe.
> +		 */
> +		I915_WRITE(CURSURFLIVE(dev_priv->psr.pipe), 0);
> +	else
> +		/*
> +		 * A write to CURSURFLIVE do not cause HW tracking to exit PSR
> +		 * on older gens so doing the manual exit instead.
> +		 */
> +		intel_psr_exit(dev_priv);
>  }
>  
>  /**
> @@ -903,6 +910,15 @@ void intel_psr_update(struct intel_dp *intel_dp,
>  		/* Force a PSR exit when enabling CRC to avoid CRC timeouts */
>  		if (crtc_state->crc_enabled && psr->enabled)
>  			psr_force_hw_tracking_exit(dev_priv);
> +		else if (INTEL_GEN(dev_priv) < 9 && psr->enabled) {
> +			/*
> +			 * Activate PSR again after a force exit when enabling
> +			 * CRC in older gens
> +			 */
> +			if (!dev_priv->psr.active &&
> +			    !dev_priv->psr.busy_frontbuffer_bits)
> +				schedule_work(&dev_priv->psr.work);
> +		}
>  
>  		goto unlock;
>  	}
> -- 
> 2.22.0
> 
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