Hi Am 07.09.23 um 10:03 schrieb Thierry Reding:
On Thu, Aug 31, 2023 at 10:04:29AM +0200, Daniel Vetter wrote:On Thu, 31 Aug 2023 at 08:33, Mikko Perttunen <cyndis@xxxxxxxx> wrote:On 8/30/23 13:19, Thomas Zimmermann wrote:Hi Am 25.08.23 um 15:22 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. Signed-off-by: Thierry Reding <treding@xxxxxxxxxx> --- drivers/gpu/drm/tegra/drm.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c index b1e1a78e30c6..7a38dadbc264 100644 --- a/drivers/gpu/drm/tegra/drm.c +++ b/drivers/gpu/drm/tegra/drm.c @@ -1220,9 +1220,11 @@ 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; + if (drm->mode_config.num_crtc > 0) {If you don't support the hardware, wouldn't it be better to return -ENODEV if !num_crtc?While display is not supported through TegraDRM on Tegra234+, certain multimedia accelerators are supported, so we need to finish probe for those.Ideally you also register the tegra driver without DRIVER_MODESET | DRIVER_ATOMIC in that case, to avoid unecessary userspace confusion. Most userspace can cope with a display driver without any crtc, but I think xorg-modesettting actually falls over. Or at least I've seen some hacks that the agx people added to make sure X doesn't accidentally open the wrong driver.That's a good point. However I recall from earlier attempts at doing something like this in Nouveau (although this is now very long ago) that it's not very easy. The problem, as I recall, is that the driver is a singleton, so we would essentially be supporting either modesetting or not, for any device in the system.
Take a look at struct drm_device.driver_features. It let's you clear the flags that your device doesn't support.
https://elixir.bootlin.com/linux/v6.5/source/include/drm/drm_device.h#L128 Best regards Thomas
Now, it's unlikely that we'd have a mix of one Tegra DRM driver with display support and another without, but it's something that I recall back at the time with Nouveau was problematic because you could have the Tegra integrated graphics (without display support) and a PCI-connected discrete GPU (with display support) within the same system. I need to look into it a bit more to see if I can come up with something good to account for this. Thierry
-- 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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