Re: [PATCH v4 0/3] drm/atomic-state-helper: fixes for blend-mode-prop warning

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Sep 02, 2026 at 08:58:37PM +0200, Melissa Wen wrote:
> 
> 
> On 01/09/2026 09:12, Thorsten Leemhuis wrote:
> > On 8/28/26 14:19, Viktor Jägersküpper wrote:
> > > On 8/28/26 09:22, Thorsten Leemhuis wrote:
> > > > On 8/27/26 19:14, Melissa Wen wrote:
> > > > > On 27/08/2026 18:37, Melissa Wen wrote:
> > > > > > On 27/08/2026 15:34, Alex Deucher wrote:
> > > > > > > On Wed, Aug 26, 2026 at 7:20 AM Melissa Wen <mwen@igalia.com> wrote:
> > > > > > > > PREMULTI was the default DRM blend mode until 9813e158d13d
> > > > > > > > ("drm/drm_blend: allow blend mode property without PREMULTI")
> > > > > > > > introduced
> > > > > > > > the possibility of exposing the blend mode property without PREMULTI
> > > > > > > > being supported. However, __drm_atomic_helper_plane_state_init() still
> > > > > > > > resets pixel_blend_mode to PREMULTI (hardcoded), ignoring the supported
> > > > > > > > mode in this property. In the same series, 860e748bddcc ("drm: ensure
> > > > > > > > blend mode supported if pixel format with alpha exposed") starts
> > > > > > > > warning
> > > > > > > > drivers that supports alpha formats in a given planes but doesn't
> > > > > > > > support blend mode property, which includes AMD primary and cursor
> > > > > > > > planes.
> > > > > [...]
> > > > > > > I presume you are planning to apply this directly to drm-misc for 7.3?
> > > > > > Right, I'll apply to drm-misc-fixes, just doing it now.
> > > > > Or not now. I have to wait for -rc1.
> > > > > I'll keep it on my radar.
> > > > Hmmm, that sounds like these fixes will miss -rc1. But wouldn't it be
> > > > good to get them included there, as they afaik (please correct me if I'm
> > > > wrong, is easy to mix something up from the outside!) the warnings that
> > > > Greg described as ""It's not good to boot and have a bunch of warnings
> > > > already happening, resulting in a "tainted" kernel before I have the
> > > > chance to break anything manually myself...""[1], as more people then
> > > > will likely encounter this (and then waste time on bisecting an issue
> > > > known for weeks for which a fix exists).
> > > > 
> > > > [1]
> > > > https://lore.kernel.org/all/2026082651-spinning-cornbread-33ba@gregkh/
> > > If I understand correctly, the *actual* fix (for all affected drivers)
> > > will make it into 7.3-rc1, see this answer to my question:
> > > https://lore.kernel.org/dri-devel/20260826-brave-nyala-of-elevation-d23aea@houat/
> > > 
> > > This fix is queued in drm-next:
> > > https://gitlab.freedesktop.org/drm/kernel/-/commit/271e90eb5f9ff34951647e5ed33c1775eebcca50
> > Ahh, yeah, many thx, I had see this downgrade to drm_warn() (which made
> > it to -rc1, yeah \o/), but had not made the right connections. :-/
> > 
> > FWIW, even with that done there is now one amdgpu regression report
> > about this already post-rc1:
> > https://lore.kernel.org/all/CANkdJ2VvJQSBzyOq=LgSW1=Z8-YiN_r9Py2iJ0UJDo55+dbfuA@mail.gmail.com/
> > 
> > """
> > [...] After updating from kernel v7.2.2 to v7.3-rc1, several DRM plane
> > warnings regarding unset blend modes for pixel formats with alpha
> > channels started appearing in dmesg during initialization.
> > 
> > [drm] [PLANE:44:plane-0] pixel format with alpha exposed but blend
> > mode not setup. Please fix. [...]
> > """
> > 
> > Will reply there now. Wondering if we need to do something about that if
> > more reports like that show up, but let's wait if that's the case.
> 
> I just applied this series to drm-misc-fixes:
> - c3080b58d81d ("drm/atomic-state-helper: set pixel_blend_mode to prop
> default on reset")
> - f0c75da0a6b4 ("drm/amd/display: fix missing blend-mode-prop warning for
> DCN")
> - 332ad707e38f ("drm/amd/display: advertise PIXEL_NONE and PREMULTI blend
> mode for DCE")
> 
> With this, the dmesg message will no longer appear on the AMD driver.

Great, thanks!