Re: [PATCH v2] drm/tegra: Remove existing framebuffer only if we support display

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Hi

Am 23.02.24 um 16:03 schrieb Thierry Reding:
From: Thierry Reding <treding@xxxxxxxxxx>

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

Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>

Makes sense as far as the aperture helpers are concerned.

Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>

Best regards
Thomas

---
  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 b1e1a78e30c6..2e1cfe6f6d74 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -1220,9 +1220,26 @@ 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)

--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)




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