[Intel-gfx] [PATCH v3 09/11] drm/i915: DisplayPort-MST pixel clock check

[Ville Syrjälä]

On Fri, Jul 31, 2015 at 03:13:58PM +0300, Mika Kahola wrote:
> It is possible the we request to have a mode that has
> higher pixel clock than our HW can support. This patch
> checks if requested pixel clock is lower than the one
> supported by the HW. The requested mode is discarded
> if we cannot support the requested pixel clock.
> 
> This patch applies to DisplayPort MST.
> 
> V2:
> - removed computation for max pixel clock
> 
> V3:
> - cleanup by removing unnecessary lines
> 
> Signed-off-by: Mika Kahola <mika.kahola at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp_mst.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index 585f0a4..fcf03d0 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -347,6 +347,8 @@ static enum drm_mode_status
>  intel_dp_mst_mode_valid(struct drm_connector *connector,
>  			struct drm_display_mode *mode)
>  {
> +	int max_pixclk = to_i915(connector->dev)->max_dotclk;

The pixclk vs. dotclk in every patch is tickling my ocd nerves. I'd say
pick one and stick to it everywhere. I guess I'm probably to blame here
since I've been using dotclock in the .get_config() paths, and pixclk
in the cdclk calculations. With grep I can't say which one is winning,
so I guess you could pick whichever seems more awesome.

Apart from that this patch looks good so:
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> +
>  	/* TODO - validate mode against available PBN for link */
>  	if (mode->clock < 10000)
>  		return MODE_CLOCK_LOW;
> @@ -354,6 +356,9 @@ intel_dp_mst_mode_valid(struct drm_connector *connector,
>  	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
>  		return MODE_H_ILLEGAL;
>  
> +	if (mode->clock > max_pixclk)
> +		return MODE_CLOCK_HIGH;
> +
>  	return MODE_OK;
>  }
>  
> -- 
> 1.9.1
> 
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-- 
Ville Syrjälä
Intel OTC