[1/2] drm/i915: Refuse modes with hdisplay==4096 on pre-HSW DP
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Message ID 20190718144340.1114-1-ville.syrjala@linux.intel.com
State New
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  • [1/2] drm/i915: Refuse modes with hdisplay==4096 on pre-HSW DP
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Commit Message

Ville Syrjälä July 18, 2019, 2:43 p.m. UTC
From: Ville Syrjälä <ville.syrjala@linux.intel.com>

The DP port/pipe goes wonky if we try to use timings with
hdisplay==4096 on pre-HSW platforms. The link fails to train
and the pipe may not signal vblank interrupts. On HDMI such at
mode works just fine (tested on ELK/SNB/CHV). So let's refuse
such modes on DP on older platforms.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

Comments

Manasi Navare July 29, 2019, 7:11 p.m. UTC | #1
On Thu, Jul 18, 2019 at 05:43:39PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> The DP port/pipe goes wonky if we try to use timings with
> hdisplay==4096 on pre-HSW platforms. The link fails to train
> and the pipe may not signal vblank interrupts. On HDMI such at
> mode works just fine (tested on ELK/SNB/CHV). So let's refuse
> such modes on DP on older platforms.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Makes sense if the link is not able to get trained that we reject this mode

> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 0eb5d66f87a7..c96030761eae 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -493,6 +493,25 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
>  	return 0;
>  }
>  
> +static bool intel_dp_hdisplay_bad(struct drm_i915_private *dev_priv,
> +				  int hdisplay)
> +{
> +	/*
> +	 * Older platforms don't like hdisplay==4096 with DP.
> +	 *
> +	 * On ILK/SNB/IVB the pipe seems to be somewhat running (scanline
> +	 * and frame counter increment), but we don't get vblank interrupts,
> +	 * and the pipe underruns immediately. The link also doesn't seem
> +	 * to get trained properly.
> +	 *
> +	 * On CHV the vblank interrupts don't seem to disappear but
> +	 * otherwise the symptoms are similar.
> +	 *
> +	 * TODO: confirm the behaviour on HSW+
> +	 */
> +	return hdisplay == 4096 && !HAS_DDI(dev_priv);
> +}
> +
>  static enum drm_mode_status
>  intel_dp_mode_valid(struct drm_connector *connector,
>  		    struct drm_display_mode *mode)
> @@ -528,6 +547,9 @@ intel_dp_mode_valid(struct drm_connector *connector,
>  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
>  	mode_rate = intel_dp_link_required(target_clock, 18);
>  
> +	if (intel_dp_hdisplay_bad(dev_priv, mode->hdisplay))
> +		return MODE_H_ILLEGAL;
> +
>  	/*
>  	 * Output bpp is stored in 6.4 format so right shift by 4 to get the
>  	 * integer value since we support only integer values of bpp.
> @@ -2208,6 +2230,9 @@ intel_dp_compute_config(struct intel_encoder *encoder,
>  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
>  		return -EINVAL;
>  
> +	if (intel_dp_hdisplay_bad(dev_priv, adjusted_mode->crtc_hdisplay))
> +		return -EINVAL;

Why would we need another check in compute_config() since the mode would have been
rejected already in intel_dp_mode_valid()

Manasi

> +
>  	ret = intel_dp_compute_link_config(encoder, pipe_config, conn_state);
>  	if (ret < 0)
>  		return ret;
> -- 
> 2.21.0
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
Ville Syrjälä Aug. 19, 2019, 4:14 p.m. UTC | #2
On Mon, Jul 29, 2019 at 12:11:58PM -0700, Manasi Navare wrote:
> On Thu, Jul 18, 2019 at 05:43:39PM +0300, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > The DP port/pipe goes wonky if we try to use timings with
> > hdisplay==4096 on pre-HSW platforms. The link fails to train
> > and the pipe may not signal vblank interrupts. On HDMI such at
> > mode works just fine (tested on ELK/SNB/CHV). So let's refuse
> > such modes on DP on older platforms.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Makes sense if the link is not able to get trained that we reject this mode
> 
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 0eb5d66f87a7..c96030761eae 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -493,6 +493,25 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> >  	return 0;
> >  }
> >  
> > +static bool intel_dp_hdisplay_bad(struct drm_i915_private *dev_priv,
> > +				  int hdisplay)
> > +{
> > +	/*
> > +	 * Older platforms don't like hdisplay==4096 with DP.
> > +	 *
> > +	 * On ILK/SNB/IVB the pipe seems to be somewhat running (scanline
> > +	 * and frame counter increment), but we don't get vblank interrupts,
> > +	 * and the pipe underruns immediately. The link also doesn't seem
> > +	 * to get trained properly.
> > +	 *
> > +	 * On CHV the vblank interrupts don't seem to disappear but
> > +	 * otherwise the symptoms are similar.
> > +	 *
> > +	 * TODO: confirm the behaviour on HSW+
> > +	 */
> > +	return hdisplay == 4096 && !HAS_DDI(dev_priv);
> > +}
> > +
> >  static enum drm_mode_status
> >  intel_dp_mode_valid(struct drm_connector *connector,
> >  		    struct drm_display_mode *mode)
> > @@ -528,6 +547,9 @@ intel_dp_mode_valid(struct drm_connector *connector,
> >  	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
> >  	mode_rate = intel_dp_link_required(target_clock, 18);
> >  
> > +	if (intel_dp_hdisplay_bad(dev_priv, mode->hdisplay))
> > +		return MODE_H_ILLEGAL;
> > +
> >  	/*
> >  	 * Output bpp is stored in 6.4 format so right shift by 4 to get the
> >  	 * integer value since we support only integer values of bpp.
> > @@ -2208,6 +2230,9 @@ intel_dp_compute_config(struct intel_encoder *encoder,
> >  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
> >  		return -EINVAL;
> >  
> > +	if (intel_dp_hdisplay_bad(dev_priv, adjusted_mode->crtc_hdisplay))
> > +		return -EINVAL;
> 
> Why would we need another check in compute_config() since the mode would have been
> rejected already in intel_dp_mode_valid()

The connector .mode_valid() won't be called for setcrtc/atomic ioctls.
It's only used to filter out the modes from the connector's mode list.

> 
> Manasi
> 
> > +
> >  	ret = intel_dp_compute_link_config(encoder, pipe_config, conn_state);
> >  	if (ret < 0)
> >  		return ret;
> > -- 
> > 2.21.0
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx

Patch
diff mbox series

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 0eb5d66f87a7..c96030761eae 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -493,6 +493,25 @@  int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
 	return 0;
 }
 
+static bool intel_dp_hdisplay_bad(struct drm_i915_private *dev_priv,
+				  int hdisplay)
+{
+	/*
+	 * Older platforms don't like hdisplay==4096 with DP.
+	 *
+	 * On ILK/SNB/IVB the pipe seems to be somewhat running (scanline
+	 * and frame counter increment), but we don't get vblank interrupts,
+	 * and the pipe underruns immediately. The link also doesn't seem
+	 * to get trained properly.
+	 *
+	 * On CHV the vblank interrupts don't seem to disappear but
+	 * otherwise the symptoms are similar.
+	 *
+	 * TODO: confirm the behaviour on HSW+
+	 */
+	return hdisplay == 4096 && !HAS_DDI(dev_priv);
+}
+
 static enum drm_mode_status
 intel_dp_mode_valid(struct drm_connector *connector,
 		    struct drm_display_mode *mode)
@@ -528,6 +547,9 @@  intel_dp_mode_valid(struct drm_connector *connector,
 	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
 	mode_rate = intel_dp_link_required(target_clock, 18);
 
+	if (intel_dp_hdisplay_bad(dev_priv, mode->hdisplay))
+		return MODE_H_ILLEGAL;
+
 	/*
 	 * Output bpp is stored in 6.4 format so right shift by 4 to get the
 	 * integer value since we support only integer values of bpp.
@@ -2208,6 +2230,9 @@  intel_dp_compute_config(struct intel_encoder *encoder,
 	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
 		return -EINVAL;
 
+	if (intel_dp_hdisplay_bad(dev_priv, adjusted_mode->crtc_hdisplay))
+		return -EINVAL;
+
 	ret = intel_dp_compute_link_config(encoder, pipe_config, conn_state);
 	if (ret < 0)
 		return ret;