Re: [PATCH] drm/i915/dp/mst: Validate modes against the available link bandwidth

[Jim Bride <jim.bride@linux.intel.com>]

On Thu, Aug 18, 2016 at 05:11:31PM -0700, Anusha Srivatsa wrote:
> Change intel_dp_mst_mode_valid() to use available link bandwidth
> rather than the link's maximum supported bandwidth to evaluate
> whether modes are legal for the current configuration. This takes
> into account the fact that link bandwidth may already be dedicated
> to other virtual channels.
> 
> Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>

Reviewed-by: Jim Bride <jim.bride@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/intel_dp_mst.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index 629337d..39c58eb 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -352,16 +352,22 @@ static enum drm_mode_status
>  intel_dp_mst_mode_valid(struct drm_connector *connector,
>  			struct drm_display_mode *mode)
>  {
> -	int max_dotclk = to_i915(connector->dev)->max_dotclk_freq;
> +	int req_pbn = 0;
> +	int slots = 0;
> +	struct intel_connector *intel_connector = to_intel_connector(connector);
> +	struct intel_dp *intel_dp = intel_connector->mst_port;
> +	struct drm_dp_mst_topology_mgr *mgr = &intel_dp->mst_mgr;
> +
> +	req_pbn = drm_dp_calc_pbn_mode(mode->clock, 24);
> +	slots = drm_dp_find_vcpi_slots(mgr, req_pbn);
>  
> -	/* TODO - validate mode against available PBN for link */
>  	if (mode->clock < 10000)
>  		return MODE_CLOCK_LOW;
>  
>  	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
>  		return MODE_H_ILLEGAL;
>  
> -	if (mode->clock > max_dotclk)
> +	if (slots == -ENOSPC)
>  		return MODE_CLOCK_HIGH;
>  
>  	return MODE_OK;
> -- 
> 2.7.4
> 
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