Re: [PATCH 2/3] drm/i915/dp: Fix sink-crc reads.

[Mika Kahola <mika.kahola@intel.com>]

On Mon, 2018-04-23 at 19:56 -0700, Dhinakaran Pandiyan wrote:
> Sink crc is calculated by the sink for static frames irrespective of
> what the driver sets in TEST_SINK_START dpcd. Since PSR is the only
> use
> case for sink crc, we don't really need the sink_crc_{start, stop}
> code.
> 
> The second problem with the current implementation is vblank waits.
> Enabling vblank interrupts triggers PSR exit, which means we aren't
> really reading the correct CRC values for PSR tests. vblank waits are
> replaced by delays.
> 
> With the changes made in this patch, sink CRC is available only for
> static frames. I have tested this on a SKL laptop with PSR panel.
> 
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c |   2 +-
>  drivers/gpu/drm/i915/intel_dp.c     | 114 ++++--------------------
> ------------
>  drivers/gpu/drm/i915/intel_drv.h    |   3 +-
>  3 files changed, 15 insertions(+), 104 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c
> b/drivers/gpu/drm/i915/i915_debugfs.c
> index 2f05f5262bba..35fa1418cc07 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -2784,7 +2784,7 @@ static int i915_sink_crc(struct seq_file *m,
> void *data)
>  
>  		intel_dp = enc_to_intel_dp(state->best_encoder);
>  
> -		ret = intel_dp_sink_crc(intel_dp, crtc_state, crc);
> +		ret = intel_dp_sink_crc(intel_dp, crc);
>  		if (ret)
>  			goto err;
>  
> diff --git a/drivers/gpu/drm/i915/intel_dp.c
> b/drivers/gpu/drm/i915/intel_dp.c
> index 7dcc874b7d8f..7352ab631ea8 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3876,32 +3876,18 @@ intel_dp_configure_mst(struct intel_dp
> *intel_dp)
>  					intel_dp->is_mst);
>  }
>  
> -static int intel_dp_sink_crc_stop(struct intel_dp *intel_dp,
> -				  struct intel_crtc_state
> *crtc_state, bool disable_wa)
> +int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
>  {
> -	struct intel_digital_port *dig_port =
> dp_to_dig_port(intel_dp);
> -	struct drm_i915_private *dev_priv = to_i915(dig_port-
> >base.base.dev);
> -	struct intel_crtc *intel_crtc = to_intel_crtc(crtc_state-
> >base.crtc);
> -	u8 buf;
> -	int ret = 0;
> -	int count = 0;
> -	int attempts = 10;
> +	int count = 0, ret = 0, attempts;
>  
> -	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK, &buf) <
> 0) {
> -		DRM_DEBUG_KMS("Sink CRC couldn't be stopped
> properly\n");
> -		ret = -EIO;
> -		goto out;
> -	}
> +	for (attempts = 0; attempts < 3 && count == 0; attempts++) {
A question. How did you end up with three attempts or one and a half
frames? We used to try 6 times or 6 vblanks until we gave up trying.
Well, I don't really know the history why we have ended up with 6
attempts in the first place. 


> +		u8 buf;
>  
> -	if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_TEST_SINK,
> -			       buf & ~DP_TEST_SINK_START) < 0) {
> -		DRM_DEBUG_KMS("Sink CRC couldn't be stopped
> properly\n");
> -		ret = -EIO;
> -		goto out;
> -	}
> -
> -	do {
> -		intel_wait_for_vblank(dev_priv, intel_crtc->pipe);
> +		/* Wait for approximately half a frame, we cannot
> wait for a
> +		 * vblank interrupt as it triggers PSR exit.
> +		 */
> +		if (attempts)
> +			usleep_range(8000, 8500);
>  
>  		if (drm_dp_dpcd_readb(&intel_dp->aux,
>  				      DP_TEST_SINK_MISC, &buf) < 0)
> {
> @@ -3909,93 +3895,19 @@ static int intel_dp_sink_crc_stop(struct
> intel_dp *intel_dp,
>  			goto out;
>  		}
>  		count = buf & DP_TEST_COUNT_MASK;
> -	} while (--attempts && count);
> -
> -	if (attempts == 0) {
> -		DRM_DEBUG_KMS("TIMEOUT: Sink CRC counter is not
> zeroed after calculation is stopped\n");
> -		ret = -ETIMEDOUT;
>  	}
>  
> - out:
> -	if (disable_wa)
> -		hsw_enable_ips(crtc_state);
> -	return ret;
> -}
> -
> -static int intel_dp_sink_crc_start(struct intel_dp *intel_dp,
> -				   struct intel_crtc_state
> *crtc_state)
> -{
> -	struct intel_digital_port *dig_port =
> dp_to_dig_port(intel_dp);
> -	struct drm_i915_private *dev_priv = to_i915(dig_port-
> >base.base.dev);
> -	struct intel_crtc *intel_crtc = to_intel_crtc(crtc_state-
> >base.crtc);
> -	u8 buf;
> -	int ret;
> -
> -	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK_MISC,
> &buf) < 0)
> -		return -EIO;
> -
> -	if (!(buf & DP_TEST_CRC_SUPPORTED))
> -		return -ENOTTY;
> -
> -	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_SINK, &buf) <
> 0)
> -		return -EIO;
> -
> -	if (buf & DP_TEST_SINK_START) {
> -		ret = intel_dp_sink_crc_stop(intel_dp, crtc_state,
> false);
> -		if (ret)
> -			return ret;
> -	}
> -
> -	hsw_disable_ips(crtc_state);
> -
> -	if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_TEST_SINK,
> -			       buf | DP_TEST_SINK_START) < 0) {
> -		hsw_enable_ips(crtc_state);
> -		return -EIO;
> -	}
> -
> -	intel_wait_for_vblank(dev_priv, intel_crtc->pipe);
> -	return 0;
> -}
> -
> -int intel_dp_sink_crc(struct intel_dp *intel_dp, struct
> intel_crtc_state *crtc_state, u8 *crc)
> -{
> -	struct intel_digital_port *dig_port =
> dp_to_dig_port(intel_dp);
> -	struct drm_i915_private *dev_priv = to_i915(dig_port-
> >base.base.dev);
> -	struct intel_crtc *intel_crtc = to_intel_crtc(crtc_state-
> >base.crtc);
> -	u8 buf;
> -	int count, ret;
> -	int attempts = 6;
> -
> -	ret = intel_dp_sink_crc_start(intel_dp, crtc_state);
> -	if (ret)
> -		return ret;
> -
> -	do {
> -		intel_wait_for_vblank(dev_priv, intel_crtc->pipe);
> -
> -		if (drm_dp_dpcd_readb(&intel_dp->aux,
> -				      DP_TEST_SINK_MISC, &buf) < 0)
> {
> -			ret = -EIO;
> -			goto stop;
> -		}
> -		count = buf & DP_TEST_COUNT_MASK;
> -
> -	} while (--attempts && count == 0);
> -
> -	if (attempts == 0) {
> -		DRM_ERROR("Panel is unable to calculate any CRC
> after 6 vblanks\n");
> +	if (attempts == 3) {
>  		ret = -ETIMEDOUT;
> -		goto stop;
> +		goto out;
>  	}
>  
>  	if (drm_dp_dpcd_read(&intel_dp->aux, DP_TEST_CRC_R_CR, crc,
> 6) != 6) {
>  		ret = -EIO;
> -		goto stop;
> +		goto out;
>  	}
>  
> -stop:
> -	intel_dp_sink_crc_stop(intel_dp, crtc_state, true);
> +out:
>  	return ret;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/intel_drv.h
> b/drivers/gpu/drm/i915/intel_drv.h
> index 44ed248f1fe9..cacee94749e2 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1644,8 +1644,7 @@ void intel_dp_sink_dpms(struct intel_dp
> *intel_dp, int mode);
>  void intel_dp_encoder_reset(struct drm_encoder *encoder);
>  void intel_dp_encoder_suspend(struct intel_encoder *intel_encoder);
>  void intel_dp_encoder_destroy(struct drm_encoder *encoder);
> -int intel_dp_sink_crc(struct intel_dp *intel_dp,
> -		      struct intel_crtc_state *crtc_state, u8 *crc);
> +int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc);
>  bool intel_dp_compute_config(struct intel_encoder *encoder,
>  			     struct intel_crtc_state *pipe_config,
>  			     struct drm_connector_state
> *conn_state);
-- 
Mika Kahola - Intel OTC

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx