Re: [PATCH v3 14/16] drm/i915: Tweak BIOS fb reuse check

From: Paz Zcharya <pazz@chromium.org>
To: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org, Andrzej Hajda <andrzej.hajda@intel.com>
Subject: Re: [PATCH v3 14/16] drm/i915: Tweak BIOS fb reuse check
Date: Tue, 30 Jan 2024 23:26:17 +0000	[thread overview]
Message-ID: <ZbmFmRSKVsNETZsQ@google.com> (raw)
In-Reply-To: <20240116075636.6121-15-ville.syrjala@linux.intel.com>

On Tue, Jan 16, 2024 at 09:56:34AM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Currently we assume that we bind the BIOS fb exactly into the same
> ggtt address where the BIOS left it. That is about to change, and
> in order to keep intel_reuse_initial_plane_obj() working as intended
> we need to compare the original ggtt offset (called 'base' here)
> as opposed to the actual vma ggtt offset we selected. Otherwise
> the first plane could change the ggtt offset, and then subsequent
> planes would no longer notice that they are in fact using the same
> ggtt offset that the first plane was already using. Thus the reuse
> check will fail and we proceed to turn off these subsequent planes.
> 
> TODO: would probably make more sense to do the pure readout first
> for all the planes, then check for fb reuse, and only then proceed
> to pin the object into the final location in the ggtt...
> 
> Cc: Paz Zcharya <pazz@chromium.org>
> Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Hi Ville,

Thank you so much for this incredible series.
It solves the issue regarding MTL initial plane readout
that Andrzej Hajda and I worked on in
https://patchwork.freedesktop.org/patch/570811/?series=127130&rev=2
In addition, it solved the issue with the new GOP.

I tested it on two different devices with Meteor Lake and it worked perfectly:
no i915 errors, no flickers or observable issues.

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