Hi Thomas,
On Mon, Oct 14, 2019 at 4:05 PM Thomas Zimmermann <[email protected]> wrote:
> The display mode is set by converting the DRM display mode to an
> fb_info state and handling it to the fbdev driver's fb_setvar()
> function. This also requires a color depth, which we take from the
> value of struct drm_mode_config.preferred_depth
>
> Signed-off-by: Thomas Zimmermann <[email protected]>
> --- a/drivers/gpu/drm/drm_fbconv_helper.c
> +++ b/drivers/gpu/drm/drm_fbconv_helper.c
> @@ -919,6 +919,24 @@ static int
> drm_fbconv_update_fb_var_screeninfo_from_framebuffer(
> return 0;
> }
>
> +static int drm_fbconv_update_fb_var_screeninfo_from_simple_display_pipe(
> + struct fb_var_screeninfo *fb_var, struct drm_simple_display_pipe
> *pipe)
> +{
> + struct drm_plane *primary = pipe->crtc.primary;
> + struct drm_fbconv_modeset *modeset = drm_fbconv_modeset_of_pipe(pipe);
> +
> + if (primary && primary->state && primary->state->fb)
> + return drm_fbconv_update_fb_var_screeninfo_from_framebuffer(
> + fb_var, primary->state->fb,
> + modeset->fb_info->fix.smem_len);
> +
> + fb_var->xres_virtual = fb_var->xres;
> + fb_var->yres_virtual = fb_var->yres;
> + fb_var->bits_per_pixel = modeset->dev->mode_config.preferred_depth;
This looks wrong to me: IMHO bits_per_pixel should be derived from
the fourcc format of the _new_ mode to be set...
> +
> + return 0;
> +}
> +
> /**
> * drm_fbconv_simple_display_pipe_mode_valid - default implementation for
> * struct drm_simple_display_pipe_funcs.mode_valid
> @@ -950,6 +968,28 @@ bool drm_fbconv_simple_display_pipe_mode_fixup(
> struct drm_crtc *crtc, const struct drm_display_mode *mode,
> struct drm_display_mode *adjusted_mode)
> {
> + struct drm_simple_display_pipe *pipe =
> + container_of(crtc, struct drm_simple_display_pipe, crtc);
> + struct drm_fbconv_modeset *modeset = drm_fbconv_modeset_of_pipe(pipe);
> + struct fb_var_screeninfo fb_var;
> + int ret;
> +
> + if (!modeset->fb_info->fbops->fb_check_var)
> + return true;
> +
> + drm_fbconv_init_fb_var_screeninfo_from_mode(&fb_var, mode);
> +
> + ret = drm_fbconv_update_fb_var_screeninfo_from_simple_display_pipe(
> + &fb_var, &modeset->pipe);
> + if (ret)
> + return true;
> +
> + ret = modeset->fb_info->fbops->fb_check_var(&fb_var,
> modeset->fb_info);
... hence this fails if the requested mode is valid with the new
fourcc format, but invalid with the old (but preferred) depth.
E.g. due to bandwidth limitations, a high-resolution mode is valid
with a low color depth, while a high color depth is limited to lower
resolutions.
Unfortunately we do not know the new fourcc format here, as both
drm_simple_display_pipe_funcs.mode_{valid,fixup}() are passed
the mode (from drm_mode_set.mode), but not the new format (from
drm_mode_set.fb->format).
Am I missing something? Is the new format available in some other way?
Thanks!
> + if (ret < 0)
> + return false;
> +
> + drm_mode_update_from_fb_var_screeninfo(adjusted_mode, &fb_var);
> +
> return true;
> }
> EXPORT_SYMBOL(drm_fbconv_simple_display_pipe_mode_fixup);
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
