[Intel-gfx] [PATCH 2/2] Validate modes against available link bandwidth

[Pandiyan, Dhinakaran]

On Thu, 2016-08-11 at 16:41 -0700, Anusha Srivatsa wrote:
> drm/dp/mst/i915
> 
> Signed-off-by: Anusha Srivatsa <anusha.srivatsa at intel.com>
> 
> Validate the modes against available link bandwidth rather than
> maximum link bandwidth so that we have a better idea as to whether
> a proposed mode can truly run beside existing stream.

The Signed-off line follows the explanation body.
https://www.kernel.org/doc/Documentation/SubmittingPatches

> ---
>  drivers/gpu/drm/i915/intel_dp_mst.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index 629337d..e7e87d7 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -352,13 +352,23 @@ static enum drm_mode_status
>  intel_dp_mst_mode_valid(struct drm_connector *connector,
>  			struct drm_display_mode *mode)
>  {
> +	int req_pbn = 0;
> +	int avail_pbn = 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;
> +	struct drm_dp_mst_port *port = (struct drm_dp_mst_port *) (intel_connector->port);
>  	int max_dotclk = to_i915(connector->dev)->max_dotclk_freq;
>  
> -	/* TODO - validate mode against available PBN for link */
> +	avail_pbn = drm_dp_mst_get_avail_pbn(mgr, port);
> +	req_pbn = drm_dp_calc_pbn_mode(mode->clock, 24);
> +	if (req_pbn > avail_pbn)
> +		return MODE_H_ILLEGAL;
> +
>  	if (mode->clock < 10000)
>  		return MODE_CLOCK_LOW;
>  
> -	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
> +        if (mode->flags & DRM_MODE_FLAG_DBLCLK)
>  		return MODE_H_ILLEGAL;
>  
>  	if (mode->clock > max_dotclk)