Re: [PATCH 10/10] drm/i915: Leave FDI running after failed link training on LPT-H

[Paulo Zanoni <przanoni@gmail.com>]

2015-12-01 11:08 GMT-02:00  <ville.syrjala@linux.intel.com>:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Currently we disable some parts of FDI setup after a failed link
> training. But despite that we continue with the modeset as if everything
> is fine. This results in tons of noise from the state checker, and
> it means we're not following the proper modeset sequence for the rest of
> crtc enabling, nor for crtc disabling.
>
> Ideally we should abort the modeset and follow the proper disable
> suquenced to shut off everything we enabled so far, but that would
> require a big rework of the modeset code. So instead just leave FDI
> up and running in its untrained state, and log an error. This is
> what we do on older platforms too.

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>

>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ddi.c | 24 +++++++++++++++---------
>  1 file changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 76ce7c2960b6..b312a47a0654 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -675,15 +675,16 @@ void hsw_fdi_link_train(struct drm_crtc *crtc)
>                 temp = I915_READ(DP_TP_STATUS(PORT_E));
>                 if (temp & DP_TP_STATUS_AUTOTRAIN_DONE) {
>                         DRM_DEBUG_KMS("FDI link training done on step %d\n", i);
> +                       break;
> +               }
>
> -                       /* Enable normal pixel sending for FDI */
> -                       I915_WRITE(DP_TP_CTL(PORT_E),
> -                                  DP_TP_CTL_FDI_AUTOTRAIN |
> -                                  DP_TP_CTL_LINK_TRAIN_NORMAL |
> -                                  DP_TP_CTL_ENHANCED_FRAME_ENABLE |
> -                                  DP_TP_CTL_ENABLE);
> -
> -                       return;
> +               /*
> +                * Leave things enabled even if we failed to train FDI.
> +                * Results in less fireworks from the state checker.
> +                */
> +               if (i == ARRAY_SIZE(hsw_ddi_translations_fdi) * 2 - 1) {
> +                       DRM_ERROR("FDI link training failed!\n");
> +                       break;
>                 }
>
>                 temp = I915_READ(DDI_BUF_CTL(PORT_E));
> @@ -712,7 +713,12 @@ void hsw_fdi_link_train(struct drm_crtc *crtc)
>                 POSTING_READ(FDI_RX_MISC(PIPE_A));
>         }
>
> -       DRM_ERROR("FDI link training failed!\n");
> +       /* Enable normal pixel sending for FDI */
> +       I915_WRITE(DP_TP_CTL(PORT_E),
> +                  DP_TP_CTL_FDI_AUTOTRAIN |
> +                  DP_TP_CTL_LINK_TRAIN_NORMAL |
> +                  DP_TP_CTL_ENHANCED_FRAME_ENABLE |
> +                  DP_TP_CTL_ENABLE);
>  }
>
>  void intel_ddi_init_dp_buf_reg(struct intel_encoder *encoder)
> --
> 2.4.10
>
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-- 
Paulo Zanoni
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