Re: [PATCH stable-5.15] drm/i915: Workaround broken BIOS DBUF configuration on TGL/RKL

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Mar 07, 2022 at 06:56:07PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> commit 4e6f55120c7eccf6f9323bb681632e23cbcb3f3c upstream.
> 
> On TGL/RKL the BIOS likes to use some kind of bogus DBUF layout
> that doesn't match what the spec recommends. With a single active
> pipe that is not going to be a problem, but with multiple pipes
> active skl_commit_modeset_enables() goes into an infinite loop
> since it can't figure out any order in which it can commit the
> pipes without causing DBUF overlaps between the planes.
> 
> We'd need some kind of extra DBUF defrag stage in between to
> make the transition possible. But that is clearly way too complex
> a solution, so in the name of simplicity let's just sanitize the
> DBUF state by simply turning off all planes when we detect a
> pipe encroaching on its neighbours' DBUF slices. We only have
> to disable the primary planes as all other planes should have
> already been disabled (if they somehow were enabled) by
> earlier sanitization steps.
> 
> And for good measure let's also sanitize in case the DBUF
> allocations of the pipes already seem to overlap each other.
> 
> Cc: <stable@vger.kernel.org> # v5.14+
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4762
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Link: https://patchwork.freedesktop.org/patch/msgid/20220204141818.1900-3-ville.syrjala@linux.intel.com
> Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> (cherry picked from commit 15512021eb3975a8c2366e3883337e252bb0eee5)
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> (cherry picked from commit 4e6f55120c7eccf6f9323bb681632e23cbcb3f3c)
> ---
> The chain of additional cherry-picks needed to get
> intel_plane_disable_noatomic() destaticed looked pretty
> hairy, so I just fixed it up manually.

Now queued up, thanks.

greg k-h