linux-kernel - Re: [PATCH v2] drm/virtio: Add suppport for non-native buffer formats

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Date:   Thu, 16 Nov 2023 14:22:20 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Christian Zigotzky <chzigotzky@...osoft.de>,
        David Airlie <airlied@...hat.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Laurent Vivier <lvivier@...hat.com>,
        Hamza Mahfooz <hamza.mahfooz@....com>,
        linux-m68k@...ts.linux-m68k.org
Cc:     dri-devel@...ts.freedesktop.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH v2] drm/virtio: Add suppport for non-native buffer formats

Geert Uytterhoeven <geert@...ux-m68k.org> writes:

> When using virtgpu on a big-endian machine, e.g. powerpc QEMU:
>
>     virtio-pci 0000:00:02.0: [drm] *ERROR* fbdev: Failed to setup generic emulation (ret=-2)
>
> or m68k/virt:
>
>     virtio-mmio virtio-mmio.125: [drm] *ERROR* fbdev: Failed to setup generic emulation (ret=-2)
>
> and the graphical display fails to come up.
>
> Before, the call to drm_mode_addfb() caused a translation from a fourcc
> format (XR24) to a bpp/depth pair (32/24) to a potentially different fourcc
> format (BX24 on big-endian), due to the quirk processing in
> drm_driver_legacy_fb_format().  After, the original fourcc format (XR24)
> is passed unmodified.
>
> However, the virtgpu DRM driver supports only a single format for its
> main plane: DRM_FORMAT_HOST_XRGB8888, which is XR24 on little-endian,
> and BX24 on big-endian.  I.e. on big-endian, virtgpu does not support
> XR24, which is the default DRM format, and must be supported by all
> drivers.  Before, this was reported, but didn't lead to a failure:
>
>     virtio-mmio virtio-mmio.125: [drm] bpp/depth value of 32/24 not supported
>     virtio-mmio virtio-mmio.125: [drm] No compatible format found
>
> As the core virtgpu driver and device support both XR24 and BX24 on both
> little-endian and big-endian just fine, fix this extending the list of
> supported formats for main plane and cursor plane to XR24/BX24 resp.
> AR24/BA24.
>
> Fixes: 6ae2ff23aa43a0c4 ("drm/client: Convert drm_client_buffer_addfb() to drm_mode_addfb2()")
> Reported-by: Christian Zigotzky <chzigotzky@...osoft.de>
> Closes: https://lore.kernel.org/r/c47fba21-3ae9-4021-9f4a-09c2670ebdbc@xenosoft.de
> Suggested-by: Gerd Hoffmann <kraxel@...hat.com>
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
> v2:
>   - Fix truncated one-line summary.
> ---

Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat