Re: [PATCH 3/3] drm/i915: Enforce max hdisplay/hblank_start limits on HSW/BDW FDI

[Paulo Zanoni <paulo.r.zanoni@intel.com>]

Em Sex, 2018-06-15 às 20:44 +0300, Ville Syrjala escreveu:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> The PCH transcoder registers are only 12 bits wide for the hdisplay
> and hblank_start values. On HSW/BDW the CPU side registers are 13
> bits wide. intel_mode_valid() only checks against the higher limit
> (since we don't know where the mode is to be used), so an extra
> check is required against the FDI limits.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_crt.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_crt.c
> b/drivers/gpu/drm/i915/intel_crt.c
> index 95aa29cf2d9c..457b1a2d05b8 100644
> --- a/drivers/gpu/drm/i915/intel_crt.c
> +++ b/drivers/gpu/drm/i915/intel_crt.c
> @@ -333,6 +333,10 @@ intel_crt_mode_valid(struct drm_connector
> *connector,
>  	    (ironlake_get_lanes_required(mode->clock, 270000, 24) >
> 2))
>  		return MODE_CLOCK_HIGH;
>  
> +	/* HSW/BDW FDI limited to 4k */
> +	if (mode->hdisplay > 4096)
> +		return MODE_H_ILLEGAL;
> +
>  	return MODE_OK;
>  }
>  
> @@ -375,6 +379,11 @@ static bool hsw_crt_compute_config(struct
> intel_encoder *encoder,
>  	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLSCAN)
>  		return false;
>  
> +	/* HSW/BDW FDI limited to 4k */
> +	if (adjusted_mode->crtc_hdisplay > 4096 ||
> +	    adjusted_mode->crtc_hblank_start > 4096)
> +		return false;

Meh, doubling checks is not cool.

By the way, doesn't this chunk make more sense inside
ironlake_fdi_compute_config()?

Just to make sure: the only cases that could escape mode_valid() and
make it into compute_config() are for panel fitting, right?

With or without changes:

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

Thanks,
Paulo 

> +
>  	pipe_config->has_pch_encoder = true;
>  
>  	/* LPT FDI RX only supports 8bpc. */
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