This is a note to let you know that I've just added the patch titled
drm/tegra: Remove existing framebuffer only if we support display
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-tegra-remove-existing-framebuffer-only-if-we-sup.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d2ad98b5bc79a406ada94ad9c179453c667c90d3
Author: Thierry Reding <treding@xxxxxxxxxx>
Date: Fri Feb 23 16:03:33 2024 +0100
drm/tegra: Remove existing framebuffer only if we support display
[ Upstream commit 86bf8cfda6d2a6720fa2e6e676c98f0882c9d3d7 ]
Tegra DRM doesn't support display on Tegra234 and later, so make sure
not to remove any existing framebuffers in that case.
v2: - add comments explaining how this situation can come about
- clear DRIVER_MODESET and DRIVER_ATOMIC feature bits
Fixes: 6848c291a54f ("drm/aperture: Convert drivers to aperture interfaces")
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Signed-off-by: Robert Foss <rfoss@xxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20240223150333.1401582-1-thierry.reding@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index ff36171c8fb70..373bcd79257e0 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -1242,9 +1242,26 @@ static int host1x_drm_probe(struct host1x_device *dev)
drm_mode_config_reset(drm);
- err = drm_aperture_remove_framebuffers(&tegra_drm_driver);
- if (err < 0)
- goto hub;
+ /*
+ * Only take over from a potential firmware framebuffer if any CRTCs
+ * have been registered. This must not be a fatal error because there
+ * are other accelerators that are exposed via this driver.
+ *
+ * Another case where this happens is on Tegra234 where the display
+ * hardware is no longer part of the host1x complex, so this driver
+ * will not expose any modesetting features.
+ */
+ if (drm->mode_config.num_crtc > 0) {
+ err = drm_aperture_remove_framebuffers(&tegra_drm_driver);
+ if (err < 0)
+ goto hub;
+ } else {
+ /*
+ * Indicate to userspace that this doesn't expose any display
+ * capabilities.
+ */
+ drm->driver_features &= ~(DRIVER_MODESET | DRIVER_ATOMIC);
+ }
err = drm_dev_register(drm, 0);
if (err < 0)
