[PATCH 1/2] drm/i915: Update mbus in intel_dbuf_mbus_update and do it properly

[Paz Zcharya]

On Wed, Feb 28, 2024 at 10:02:12AM +0200, Stanislav Lisovskiy wrote:
> According to BSpec we need to do correspondent MBUS updates before
> or after DBUF reallocation, depending on whether we are reducing
> or increasing amount of pipes(typical scenario is swithing between
> multiple and single displays).
> 
> As of BSpec 49213 if we are swithing from multiple to single display
> MBUS registers should be updated with correspondent values _before_
> Dbuf reallocation happens, however if we are switching from single
> display to multiple then it should happen _after_ DDB reallocation(i.e
> plane programming).
> 
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
Thank you for this patch, Stanislav!
We tested it on a MTL-U based Chromebook (Screebo),
using different configurations (eDP, eDP + HDMI, HDMI, etc.), and
it worked well -- joined the mbus + no visual issues or i915 errors.

Tested-by: Paz Zcharya <pazz at chromium.org>