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micalg=pgp-sha384; protocol="application/pgp-signature"; boundary="6cnjeiuqjwcs7vod" Content-Disposition: inline In-Reply-To: <20250630113008.GD20333@pendragon.ideasonboard.com> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --6cnjeiuqjwcs7vod Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH] drm: xlnx: zynqmp_dp: Support DRM_FORMAT_XRGB8888 MIME-Version: 1.0 On Mon, Jun 30, 2025 at 02:30:08PM +0300, Laurent Pinchart wrote: > On Mon, Jun 30, 2025 at 12:52:48PM +0200, Maxime Ripard wrote: > > On Mon, Jun 30, 2025 at 12:33:35PM +0300, Laurent Pinchart wrote: > > > On Mon, Jun 30, 2025 at 11:29:08AM +0200, Maxime Ripard wrote: > > > > On Mon, Jun 30, 2025 at 12:11:56PM +0300, Laurent Pinchart wrote: > > > > > On Mon, Jun 30, 2025 at 10:27:55AM +0200, Maxime Ripard wrote: > > > > > > On Mon, Jun 30, 2025 at 10:03:16AM +0200, Mike Looijmans wrote: > > > > > > > On 27-06-2025 20:19, Laurent Pinchart wrote: > > > > > > > > On Fri, Jun 27, 2025 at 04:50:46PM +0200, Mike Looijmans wr= ote: > > > > > > > > > XRGB8888 is the default mode that Xorg will want to use. = Add support > > > > > > > > > for this to the Zynqmp DisplayPort driver, so that applic= ations can use > > > > > > > > > 32-bit framebuffers. This solves that the X server would = fail to start > > > > > > > > > unless one provided an xorg.conf that sets DefaultDepth t= o 16. > > > > > > > > >=20 > > > > > > > > > Signed-off-by: Mike Looijmans > > > > > > > > > --- > > > > > > > > >=20 > > > > > > > > > drivers/gpu/drm/xlnx/zynqmp_disp.c | 5 +++++ > > > > > > > > > 1 file changed, 5 insertions(+) > > > > > > > > >=20 > > > > > > > > > diff --git a/drivers/gpu/drm/xlnx/zynqmp_disp.c b/drivers= /gpu/drm/xlnx/zynqmp_disp.c > > > > > > > > > index 80d1e499a18d..501428437000 100644 > > > > > > > > > --- a/drivers/gpu/drm/xlnx/zynqmp_disp.c > > > > > > > > > +++ b/drivers/gpu/drm/xlnx/zynqmp_disp.c > > > > > > > > > @@ -312,6 +312,11 @@ static const struct zynqmp_disp_form= at avbuf_gfx_fmts[] =3D { > > > > > > > > > .buf_fmt =3D ZYNQMP_DISP_AV_BUF_FMT_NL_GFX_RGBA8888, > > > > > > > > > .swap =3D true, > > > > > > > > > .sf =3D scaling_factors_888, > > > > > > > > > + }, { > > > > > > > > > + .drm_fmt =3D DRM_FORMAT_XRGB8888, > > > > > > > > > + .buf_fmt =3D ZYNQMP_DISP_AV_BUF_FMT_NL_GFX_RGBA8888, > > > > > > > > > + .swap =3D true, > > > > > > > > > + .sf =3D scaling_factors_888, > > > > > > > >=20 > > > > > > > > I'm afraid that's not enough. There's a crucial difference = between > > > > > > > > DRM_FORMAT_ARGB8888 (already supported by this driver) and > > > > > > > > DRM_FORMAT_XRGB8888: for the latter, the 'X' component must= be ignored. > > > > > > > > The graphics layer is blended on top of the video layer, an= d the blender > > > > > > > > uses both a global alpha parameter and the alpha channel of= the graphics > > > > > > > > layer for 32-bit RGB formats. This will lead to incorrect o= peration when > > > > > > > > the 'X' component is not set to full opacity. > > > > > > >=20 > > > > > > > I spent a few hours digging in the source code and what I cou= ld find in the > > > > > > > TRM and register maps, but there's not enough information in = there to > > > > > > > explain how the blender works. The obvious "XRGB" implementat= ion would be to > > > > > > > just disable the blender. > > > > > > >=20 > > > > > > > What I got from experimenting so far is that the alpha compon= ent is ignored > > > > > > > anyway while the video path isn't active. So as long as one i= sn't using the > > > > > > > video blending path, the ARGB and XRGB modes are identical. > > > > > > >=20 > > > > > > > Guess I'll need assistance from AMD/Xilinx to completely impl= ement the XRGB > > > > > > > modes. > > > > > > >=20 > > > > > > > (For our application, this patch is sufficient as it solves t= he issues like > > > > > > > X11 not starting up, OpenGL not working and horrendously slow= scaling > > > > > > > performance) > > > > > >=20 > > > > > > Given that we consider XRGB8888 mandatory, > > > > >=20 > > > > > How about platforms that can't support it at all ? > > > >=20 > > > > We emulate it. > > >=20 > > > Does that imply a full memcpy of the frame buffer in the kernel drive= r, > > > or is it emulated in userspace ? > >=20 > > Neither :) > >=20 > > The kernel deals with it through drm_fb_xrgb8888_to_* helpers, but only > > on the parts of the framebuffer that were modified through the damage > > API. >=20 > Aahhh OK, it's for the fbdev emulation. So that means that drivers are > not required to support XRGB8888 ? No, it's for KMS. Maxime --6cnjeiuqjwcs7vod Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJUEABMJAB0WIQTkHFbLp4ejekA/qfgnX84Zoj2+dgUCaGJ5kgAKCRAnX84Zoj2+ dtHkAXwNtyyEjsQUv8JQdIBXT6tm3KJUjlzGhpdjE5afhE4oZw2ADEyDXOnl54o2 NwOIvLUBf3Mz48PkLBlxwmZ/gjbSF8CEQWhXESLyMBhNlyn/SG1J5QxjCXKVIxfO /sSVScdEYA== =AOip -----END PGP SIGNATURE----- --6cnjeiuqjwcs7vod--