Re: [PATCH v3 06/11] drm/i915: DSI pixel clock check

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Jul 31, 2015 at 03:13:55PM +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 DSI.
> 
> V2:
> - removed computation for max pixel clock
> 
> V3:
> - cleanup by removing unnecessary lines
> 
> Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dsi.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
> index 18dd7d7..3def6f9 100644
> --- a/drivers/gpu/drm/i915/intel_dsi.c
> +++ b/drivers/gpu/drm/i915/intel_dsi.c
> @@ -654,6 +654,7 @@ intel_dsi_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;
>  
>  	DRM_DEBUG_KMS("\n");
>  
> @@ -669,6 +670,9 @@ intel_dsi_mode_valid(struct drm_connector *connector,
>  			return MODE_PANEL;
>  	}
>  
> +	if (mode->clock > max_pixclk)
> +		return MODE_CLOCK_HIGH;
> +

Hmm. Seems like this too ought to be checking the fixed_mode.
intel_dsi_mode_valid() seems to assume there could be no fixed mode,
but looking at intel_dsi_init() tells me that can't be (if we ignore the
totally broken looking error handling).

Also we don't set up the panel fitter in the DSI code even though the
presence of fixed_mode clearly indicates that we should. So the whole
thing seems more or less busted.

For now, I think just sticking the clock check inside the 'if (fixed_mode)'
block would be fine, and then someone can try to clean up the bigger
mess.

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