Re: [PATCH v2] drm/i915: Ignore TMDS clock limit for DP++ when EDID override is set

[Jani Nikula <jani.nikula@intel.com>]

On Fri, 15 Dec 2017, Abdiel Janulgue <abdiel.janulgue@linux.intel.com> wrote:
> 4K modes testing by using dummy EDID data has never been working
> properly on boxes with DP++ (dual-mode) adaptors. The reason for
> this is that those modes got pruned during hdmi mode validation.
> intel_hdmi_mode_valid returns CLOCK_HIGH because the pixel clock
> reported by the 4k mode is higher than dual port TMDS clock limit.
>
> However 4k injection does work properly on machines that don't have
> DP++ adapters because the mode is never validated against the DP++
> TMDS clock limit.
>
> v2: Don't detect the DP++ limits when we're testing using overridden
>     EDIDs. Make sure to check for the override condition after
>     respecting the value of drm_dp_dual_mode_detect (Jani Nikula).
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101649
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>

I have this vague wish we had a better way to do this, but at the same
time I have no reason to block this patch either. It's debugfs, not an
ABI, and we can change this again if we come up with something better.

Pushed, thanks for the patch and for your patience with my
procrastination.

BR,
Jani.



> ---
>  drivers/gpu/drm/i915/intel_hdmi.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index bced7b9..9834690 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1567,7 +1567,10 @@ intel_hdmi_dp_dual_mode_detect(struct drm_connector *connector, bool has_edid)
>  	 * there's nothing connected to the port.
>  	 */
>  	if (type == DRM_DP_DUAL_MODE_UNKNOWN) {
> -		if (has_edid &&
> +		/* An overridden EDID imply that we want this port for testing.
> +		 * Make sure not to set limits for that port.
> +		 */
> +		if (has_edid && !connector->override_edid &&
>  		    intel_bios_is_port_dp_dual_mode(dev_priv, port)) {
>  			DRM_DEBUG_KMS("Assuming DP dual mode adaptor presence based on VBT\n");
>  			type = DRM_DP_DUAL_MODE_TYPE1_DVI;

-- 
Jani Nikula, Intel Open Source Technology Center
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