[Intel-gfx] [PATCH v3 04/11] drm/i915: LVDS pixel clock check

[Ville Syrjälä]

On Fri, Jul 31, 2015 at 03:13:53PM +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 LVDS.
> 
> 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_lvds.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
> index cb634f4..59213f9 100644
> --- a/drivers/gpu/drm/i915/intel_lvds.c
> +++ b/drivers/gpu/drm/i915/intel_lvds.c
> @@ -289,11 +289,14 @@ intel_lvds_mode_valid(struct drm_connector *connector,
>  {
>  	struct intel_connector *intel_connector = to_intel_connector(connector);
>  	struct drm_display_mode *fixed_mode = intel_connector->panel.fixed_mode;
> +	int max_pixclk = to_i915(connector->dev)->max_dotclk;
>  
>  	if (mode->hdisplay > fixed_mode->hdisplay)
>  		return MODE_PANEL;
>  	if (mode->vdisplay > fixed_mode->vdisplay)
>  		return MODE_PANEL;
> +	if (mode->clock > max_pixclk)
> +		return MODE_CLOCK_HIGH;

This should really be checking fixed_mode->clock. Though checking it
every time is a bit pointless since it never changes. But what the eDP
cases ends up doing as well.

Maybe we should just stick the check to where we pick fixed_mode, or
perhaps just have intel_panel_init() print an error if the provided
modes(s) are no good? In theory that should never happen anyway.

>  
>  	return MODE_OK;
>  }
> -- 
> 1.9.1
> 
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-- 
Ville Syrjälä
Intel OTC