[Nouveau] [PATCH] drm/nouveau: Accept 'legacy' format modifiers

[James Jones]

This should resolve the inability to start X with the new NV format 
modifier support in nouveau.  FYI, I'm offline next week, but I'll check 
in tonight in case there are any review comments.  When I'm back, I'll 
get the associated userspace fixes cleaned up and out to the appropriate 
lists.

Thanks,
-James

On 7/17/20 11:57 AM, James Jones wrote:
> Accept the DRM_FORMAT_MOD_NVIDIA_16BX2_BLOCK()
> family of modifiers to handle broken userspace
> Xorg modesetting and Mesa drivers.
> 
> Tested with Xorg 1.20 modesetting driver,
> weston at c46c70dac84a4b3030cd05b380f9f410536690fc,
> gnome & KDE wayland desktops from Ubuntu 18.04,
> and sway 1.5
> 
> Signed-off-by: James Jones <jajones at nvidia.com>
> ---
>   drivers/gpu/drm/nouveau/nouveau_display.c | 26 +++++++++++++++++++++--
>   1 file changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c
> index 496c4621cc78..31543086254b 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_display.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_display.c
> @@ -191,8 +191,14 @@ nouveau_decode_mod(struct nouveau_drm *drm,
>   		   uint32_t *tile_mode,
>   		   uint8_t *kind)
>   {
> +	struct nouveau_display *disp = nouveau_display(drm->dev);
>   	BUG_ON(!tile_mode || !kind);
>   
> +	if ((modifier & (0xffull << 12)) == 0ull) {
> +		/* Legacy modifier.  Translate to this device's 'kind.' */
> +		modifier |= disp->format_modifiers[0] & (0xffull << 12);
> +	}
> +
>   	if (modifier == DRM_FORMAT_MOD_LINEAR) {
>   		/* tile_mode will not be used in this case */
>   		*tile_mode = 0;
> @@ -227,6 +233,16 @@ nouveau_framebuffer_get_layout(struct drm_framebuffer *fb,
>   	}
>   }
>   
> +static const u64 legacy_modifiers[] = {
> +	DRM_FORMAT_MOD_NVIDIA_16BX2_BLOCK(0),
> +	DRM_FORMAT_MOD_NVIDIA_16BX2_BLOCK(1),
> +	DRM_FORMAT_MOD_NVIDIA_16BX2_BLOCK(2),
> +	DRM_FORMAT_MOD_NVIDIA_16BX2_BLOCK(3),
> +	DRM_FORMAT_MOD_NVIDIA_16BX2_BLOCK(4),
> +	DRM_FORMAT_MOD_NVIDIA_16BX2_BLOCK(5),
> +	DRM_FORMAT_MOD_INVALID
> +};
> +
>   static int
>   nouveau_validate_decode_mod(struct nouveau_drm *drm,
>   			    uint64_t modifier,
> @@ -247,8 +263,14 @@ nouveau_validate_decode_mod(struct nouveau_drm *drm,
>   	     (disp->format_modifiers[mod] != modifier);
>   	     mod++);
>   
> -	if (disp->format_modifiers[mod] == DRM_FORMAT_MOD_INVALID)
> -		return -EINVAL;
> +	if (disp->format_modifiers[mod] == DRM_FORMAT_MOD_INVALID) {
> +		for (mod = 0;
> +		     (legacy_modifiers[mod] != DRM_FORMAT_MOD_INVALID) &&
> +		     (legacy_modifiers[mod] != modifier);
> +		     mod++);
> +		if (legacy_modifiers[mod] == DRM_FORMAT_MOD_INVALID)
> +			return -EINVAL;
> +	}
>   
>   	nouveau_decode_mod(drm, modifier, tile_mode, kind);
>   
>