linux-kernel - Re: [PATCHv2] drm: fb_helper: prefer to use mode, which is not DRM_MODE_TYPE

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Date:	Mon, 20 Apr 2015 12:57:33 +0200
From:	Radek Dostál <rd@...ekdostal.com>
To:	Chris Wilson <chris@...is-wilson.co.uk>, airlied@...ux.ie,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2] drm: fb_helper: prefer to use mode, which is not DRM_MODE_TYPE_USERDEF

Hi Chris,

On 04/20/2015 12:48 PM, Chris Wilson wrote:
>> Unfortunately you can not do that. I already tried. At the time when
>> > drm_helper_probe_add_cmdline_mode is called EDID informations are not
>> > yet available.
> My understanding is that it should be. fb_helper.initial_config does a
> probe first, and the intel_fb_initial_config() should only keep the
> active mode.

uff, sorry I am not sure that I follow here - I am not that familiar
with the whole subsystem.

>> > Only option would be to remove the GTF cmdline mode, when matching mode
>> > is found in EDID.
> So basically
> 
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index 6350387..9212bec 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -79,13 +79,29 @@ drm_mode_validate_flag(const struct drm_display_mode *mode,
>  
>  static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
>  {
> +       struct drm_cmdline_mode *cmdline_mode;
>         struct drm_display_mode *mode;
>  
> -       if (!connector->cmdline_mode.specified)
> +       cmdline_mode = &connector->cmdline_mode;
> +       if (!cmdline_mode->specified)
>                 return 0;
>  
> +       /* Only add a GTF mode if we find no matching probed modes */
> +       list_for_each_entry(mode, &connector->modes, head) {
> +               if (mode->hdisplay != cmdline_mode->xres ||
> +                   mode->vdisplay != cmdline_mode->yres)
> +                       continue;
> +
> +               if (cmdline_mode->refresh_specified) {
> +                       if (mode->vrefresh != cmdline_mode->refresh)
> +                               continue;
> +               }
> +
> +               return 0;
> +       }
> +
>         mode = drm_mode_create_from_cmdline_mode(connector->dev,
> -                                                &connector->cmdline_mode);
> +                                                cmdline_mode);
>         if (mode == NULL)
>                 return 0;
>  
> 
> 
> is not sufficient?

indeed, this was my first idea how to fix this problem, but at the time
drm_helper_probe_add_cmdline_mode is called connector->modes is empty =>
the GTF cmdline mode is still added.

Thanks,
Radek
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