Re: [Intel-gfx] [PATCH] drm/i915/hdmi: Prune modes that require HDMI2.1 FRL

["Murthy, Arun R" <arun.r.murthy@intel.com>]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces@lists.freedesktop.org> On Behalf Of Ankit
> Nautiyal
> Sent: Thursday, July 7, 2022 10:57 AM
> To: intel-gfx@lists.freedesktop.org
> Subject: [Intel-gfx] [PATCH] drm/i915/hdmi: Prune modes that require
> HDMI2.1 FRL
> 
> HDMI2.1 requires some higher resolution video modes to be enumerated
> only if HDMI2.1 Fixed Rate Link (FRL) is supported.
> Current platforms do not support FRL transmission so prune modes that
> require HDMI2.1 FRL.
>
If the hardware doesn't support FRL then it basically blocks HDMI2.1 feature.
Then it wont be possible to use any resolution above 4k60 is it?

> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_hdmi.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c
> b/drivers/gpu/drm/i915/display/intel_hdmi.c
> index ebd91aa69dd2..93c00b61795f 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> @@ -1974,6 +1974,20 @@ intel_hdmi_mode_clock_valid(struct
> drm_connector *connector, int clock,
>  	return status;
>  }
> 
> +/*
> + * HDMI2.1 requires higher resolution modes like 8k60, 4K120 to be
> + * enumerated only if FRL is supported. Platforms not supporting FRL
> + * must prune these modes.
> + */
> +static bool
> +hdmi21_frl_quirk(int dotclock, bool frl_supported) {
> +	if (dotclock >= 600000 && !frl_supported)
> +		return true;
> +
> +	return false;
> +}
> +
>  static enum drm_mode_status
>  intel_hdmi_mode_valid(struct drm_connector *connector,
>  		      struct drm_display_mode *mode)
> @@ -2001,6 +2015,13 @@ intel_hdmi_mode_valid(struct drm_connector
> *connector,
>  		clock *= 2;
>  	}
> 
> +	/*
> +	 * Current Platforms do not support HDMI2.1 FRL mode of
> transmission,
> +	 * so prune the modes that require FRL.
> +	 */
> +	if (hdmi21_frl_quirk(clock, false))
> +		return MODE_BAD;
> +
Instead of setting this frl_supported as false, can we get this info from hardware, so that when
our hardware supports it later it would be easy to enable this.

Thanks and Regards,
Arun R Murthy
-------------------