[Intel-gfx] [PATCH] drm/i915: optimzie eDP 1.4 config

[Chris Wilson]

Quoting Lee, Shawn C (2018-09-04 15:55:41)
> eDP 1.4 introduce a new link rates flexibility and selection.
> It provided system specific link rate optimization and power
> efficiency. We should keep eDP 1.3 and older version to use
> max link rate approach to avoid any side effect. And eDP 1.4
> used the optimization link rate and lane count setting.
> 
> Cc: Matt Atwood <matthew.s.atwood at intel.com>
> Signed-off-by: Lee, Shawn C <shawn.c.lee at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 436c22de33b6..903d640fe712 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1953,8 +1953,10 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>                  * configuration, and typically these values correspond to the
>                  * native resolution of the panel.
>                  */

Having just finished a comment explaining why we override the limits for
eDP, the following logic is confusing without at least a mention above.

> -               limits.min_lane_count = limits.max_lane_count;
> -               limits.min_clock = limits.max_clock;
> +               if (intel_dp->edp_dpcd[0] <= DP_EDP_13) {
> +                       limits.min_lane_count = limits.max_lane_count;
> +                       limits.min_clock = limits.max_clock;
> +               }
>         }
>  
>         intel_dp_adjust_compliance_config(intel_dp, pipe_config, &limits);
> -- 
> 2.7.4
> 
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