[Intel-gfx] [PATCH 1/2] drm/i915: Try to use fast+narrow link on eDP again and fall back to the old max strategy on failure

[Ville Syrjälä]

On Thu, Jan 07, 2021 at 08:20:25PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Some new eDP panels don't like to operate at the max parameters, and
> instead we need to go for an optimal confiugration. That unfortunately
> doesn't work with older eDP panels which are generally only guaranteed
> to work at the max parameters.
> 
> To solve these two conflicting requirements let's start with the optimal
> setup, and if that fails we start again with the max parameters. The
> downside is probably an extra modeset when we switch strategies but
> I don't see a good way to avoid that.
> 
> For a bit of history we first tried to go for the fast+narrow in
> commit 7769db588384 ("drm/i915/dp: optimize eDP 1.4+ link config
> fast and narrow"). but that had to be reverted due to regression
> on older panels in commit f11cb1c19ad0 ("drm/i915/dp: revert back
> to max link rate and lane count on eDP"). So now we try to get
> the best of both worlds by using both strategies.

Pushed. Fingers crossed for no regressions...

-- 
Ville Syrjälä
Intel