[PATCH 6.7 061/162] drm/tegra: Remove existing framebuffer only if we support display

Greg Kroah-Hartman
2024-03-04T21:28:33Z

From: Thierry Reding <treding@nvidia.com>

[ 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@nvidia.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240223150333.1401582-1-thierry.reding@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/tegra/drm.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)

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)
--
2.43.0