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 11:36:04 +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 11:09 AM, Chris Wilson wrote:
> The EDID modes should be earlier in the list, and so higher priority
> than the cmdline mode. The only instance I see that breaking down is if
> the mode gets created by drm_pick_cmdline_mode, i.e.

indeed at the beginning the command line mode is added to the end of the
list, but later on it seems to me that all modes are reordered based on
the resolution and clock and than mode generated by
drm_helper_probe_add_cmdline_mode gets upper in the list as it has
higher clock value. Please see attached output of dmesg.

Additionally I am attaching the output with commit eaf99c749d43
reverted, where you can see that the mode "1280x720@60 with pixel clock
74440" is not even added to the list.

> diff --git a/drivers/gpu/drm/drm_fb_helper.c
b/drivers/gpu/drm/drm_fb_helper.c
> index cac422916c7a..d55c2de6a99f 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1327,7 +1327,7 @@ again:
>  create_mode:
>         mode =
drm_mode_create_from_cmdline_mode(fb_helper_conn->connector->dev,
>                                                  cmdline_mode);
> -       list_add(&mode->head, &fb_helper_conn->connector->modes);
> +       list_add_tail(&mode->head, &fb_helper_conn->connector->modes);
>         return mode;
>  }
>  EXPORT_SYMBOL(drm_pick_cmdline_mode);

I am pretty sure, this will not help as in my case it never makes it to
create_mode.

Thanks,
Radek

View attachment "dmesg" of type "text/plain" (32725 bytes)

View attachment "with-revert" of type "text/plain" (32344 bytes)