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

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Date:   Thu, 16 Nov 2023 14:16:54 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     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>,
        Javier Martinez Canillas <javierm@...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: [PATCH v2] drm/virtio: Add suppport for non-native buffer formats

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.
---
 drivers/gpu/drm/virtio/virtgpu_display.c | 11 +++++++++--
 drivers/gpu/drm/virtio/virtgpu_plane.c   |  6 ++++--
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_display.c b/drivers/gpu/drm/virtio/virtgpu_display.c
index ad924a8502e9025c..49c89000aec33f23 100644
--- a/drivers/gpu/drm/virtio/virtgpu_display.c
+++ b/drivers/gpu/drm/virtio/virtgpu_display.c
@@ -301,9 +301,16 @@ virtio_gpu_user_framebuffer_create(struct drm_device *dev,
 	struct virtio_gpu_framebuffer *virtio_gpu_fb;
 	int ret;
 
-	if (mode_cmd->pixel_format != DRM_FORMAT_HOST_XRGB8888 &&
-	    mode_cmd->pixel_format != DRM_FORMAT_HOST_ARGB8888)
+	switch (mode_cmd->pixel_format) {
+	case DRM_FORMAT_XRGB8888:
+	case DRM_FORMAT_ARGB8888:
+	case DRM_FORMAT_BGRX8888:
+	case DRM_FORMAT_BGRA8888:
+		break;
+
+	default:
 		return ERR_PTR(-ENOENT);
+	}
 
 	/* lookup object associated with res handle */
 	obj = drm_gem_object_lookup(file_priv, mode_cmd->handles[0]);
diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c
index a2e045f3a0004a1b..a547d76b8fb0a77d 100644
--- a/drivers/gpu/drm/virtio/virtgpu_plane.c
+++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
@@ -30,11 +30,13 @@
 #include "virtgpu_drv.h"
 
 static const uint32_t virtio_gpu_formats[] = {
-	DRM_FORMAT_HOST_XRGB8888,
+	DRM_FORMAT_XRGB8888,
+	DRM_FORMAT_BGRX8888,
 };
 
 static const uint32_t virtio_gpu_cursor_formats[] = {
-	DRM_FORMAT_HOST_ARGB8888,
+	DRM_FORMAT_ARGB8888,
+	DRM_FORMAT_BGRA8888,
 };
 
 uint32_t virtio_gpu_translate_format(uint32_t drm_fourcc)
-- 
2.34.1