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

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 23.02.24 um 16:03 schrieb Thierry Reding:
> From: Thierry Reding <treding@nvidia.com>
>
> 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@nvidia.com>

Makes sense as far as the aperture helpers are concerned.

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

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)