[Intel-gfx] [PATCH] drm/edid: Reset more of the display info

[Daniel Vetter]

On Tue, Apr 24, 2018 at 04:02:50PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> We're currently failing to reset everything in display_info.hdmi
> which will potentially cause us to use stale information when
> swapping monitors. Eg. if the user replaces a HDMI 2.0 monitor
> with a HDMI 1.x monitor we will continue to think that the monitor
> supports scrambling. That will lead to a black screen since the
> HDMI 1.x monitor won't understand the scrambled signal.
> 
> Fix the problem by clearing display_info.hdmi fully. And while at
> eliminate some duplicated code by calling drm_reset_display_info()
> in drm_add_display_info().
> 
> Cc: Antony Chen <antonychen at qnap.com>
> Cc: Shashank Sharma <shashank.sharma at intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105655
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 134069f36482..39f1db4acda4 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4451,6 +4451,7 @@ drm_reset_display_info(struct drm_connector *connector)
>  	info->max_tmds_clock = 0;
>  	info->dvi_dual = false;
>  	info->has_hdmi_infoframe = false;
> +	memset(&info->hdmi, 0, sizeof(info->hdmi));
>  
>  	info->non_desktop = 0;
>  }
> @@ -4462,17 +4463,11 @@ u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edi
>  
>  	u32 quirks = edid_get_quirks(edid);
>  
> +	drm_reset_display_info(connector);
> +

Strictly speaking this is a separate bugfix, for the case where you
immediately go from one output to a different one. Keith already fixed the
case where at least somewhere in between you go to the disconnected state
in:

commit 170178fe99dd212bf25e70c89bc4b6e195564ffc
Author: Keith Packard <keithp at keithp.com>
Date:   Wed Dec 13 00:44:26 2017 -0800

    drm: Update edid-derived drm_display_info fields at edid property set [v2]

With the above explained in the commit message:

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

>  	info->width_mm = edid->width_cm * 10;
>  	info->height_mm = edid->height_cm * 10;
>  
> -	/* driver figures it out in this case */
> -	info->bpc = 0;
> -	info->color_formats = 0;
> -	info->cea_rev = 0;
> -	info->max_tmds_clock = 0;
> -	info->dvi_dual = false;
> -	info->has_hdmi_infoframe = false;
> -
>  	info->non_desktop = !!(quirks & EDID_QUIRK_NON_DESKTOP);
>  
>  	DRM_DEBUG_KMS("non_desktop set to %d\n", info->non_desktop);
> -- 
> 2.16.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch