[Intel-gfx] [PATCH] drm/i915/hdmi: Go for scrambling only if platform supports TMDS clock > 340MHz

[Murthy, Arun R]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Ankit
> Nautiyal
> Sent: Tuesday, December 13, 2022 11:21 AM
> To: intel-gfx at lists.freedesktop.org
> Subject: [Intel-gfx] [PATCH] drm/i915/hdmi: Go for scrambling only if
> platform supports TMDS clock > 340MHz
> 
> There are cases, where devices have an HDMI1.4 retimer, and TMDS clock
> rate is capped to 340MHz via VBT. In such cases scrambling might be
> supported by the platform and an HDMI2.0 sink for lower TMDS rates, but
> not supported by the retimer, causing blankouts.
> 
> So avoid enabling scrambling, if the TMDS clock is capped to <= 340MHz.
> 
Doesn't this clash with scrambling with low rates?

Thanks and Regards,
Arun R Murthy
--------------------
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_hdmi.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c
> b/drivers/gpu/drm/i915/display/intel_hdmi.c
> index efa2da080f62..c124fe667bc0 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> @@ -2244,6 +2244,11 @@ static bool intel_hdmi_is_cloned(const struct
> intel_crtc_state *crtc_state)
>  		!is_power_of_2(crtc_state->uapi.encoder_mask);
>  }
> 
> +static bool source_can_support_scrambling(struct intel_encoder
> +*encoder) {
> +	return intel_hdmi_source_max_tmds_clock(encoder) > 340000; }
> +
>  int intel_hdmi_compute_config(struct intel_encoder *encoder,
>  			      struct intel_crtc_state *pipe_config,
>  			      struct drm_connector_state *conn_state) @@ -
> 2301,7 +2306,7 @@ int intel_hdmi_compute_config(struct intel_encoder
> *encoder,
> 
>  	pipe_config->lane_count = 4;
> 
> -	if (scdc->scrambling.supported && DISPLAY_VER(dev_priv) >= 10) {
> +	if (scdc->scrambling.supported &&
> +source_can_support_scrambling(encoder)) {
>  		if (scdc->scrambling.low_rates)
>  			pipe_config->hdmi_scrambling = true;
> 
> --
> 2.25.1