Re: [Intel-gfx] [PATCH] drm/i915: Get HDR DPCD refresh timeout from VBT

[Lyude Paul <lyude@redhat.com>]

BTW - I just started catching up with my email, is this waiting on me or was
someone else able to review it?

On Mon, 2023-02-20 at 18:47 +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Grab the HDR DPCD refresh timeout (time we need to wait after
> writing the sourc OUI before the HDR DPCD registers are ready)
> from the VBT.
> 
> Windows doesn't even seem to have any default value for this,
> which is perhaps a bit weird since the VBT value is documented
> as TGL+ and I thought the HDR backlight stuff might already be
> used on earlier platforms. To play it safe I left the old
> hardcoded 30ms default in place. Digging through some internal
> stuff that seems to have been a number given by the vendor for
> one particularly slow TCON. Although I did see 50ms mentioned
> somewhere as well.
> 
> Let's also include the value in the debug print to ease
> debugging, and toss in the customary connector id+name as well.
> 
> The TGL Thinkpad T14 I have sets this to 0 btw. So the delay
> is now gone on this machine:
>  [CONNECTOR:308:eDP-1] Detected Intel HDR backlight interface version 1
>  [CONNECTOR:308:eDP-1] Using Intel proprietary eDP backlight controls
>  [CONNECTOR:308:eDP-1] SDR backlight is controlled through PWM
>  [CONNECTOR:308:eDP-1] Using native PCH PWM for backlight control (controller=0)
>  [CONNECTOR:308:eDP-1] Using AUX HDR interface for backlight control (range 0..496)
>  [CONNECTOR:308:eDP-1] Performing OUI wait (0 ms)
> 
> Cc: Lyude Paul <lyude@redhat.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_bios.c          | 6 ++++++
>  drivers/gpu/drm/i915/display/intel_display_types.h | 1 +
>  drivers/gpu/drm/i915/display/intel_dp.c            | 9 +++++++--
>  3 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> index f35ef3675d39..f16887aed56d 100644
> --- a/drivers/gpu/drm/i915/display/intel_bios.c
> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> @@ -1084,6 +1084,12 @@ parse_lfp_backlight(struct drm_i915_private *i915,
>  		panel->vbt.backlight.min_brightness = entry->min_brightness;
>  	}
>  
> +	if (i915->display.vbt.version >= 239)
> +		panel->vbt.backlight.hdr_dpcd_refresh_timeout =
> +			DIV_ROUND_UP(backlight_data->hdr_dpcd_refresh_timeout[panel_type], 100);
> +	else
> +		panel->vbt.backlight.hdr_dpcd_refresh_timeout = 30;
> +
>  	drm_dbg_kms(&i915->drm,
>  		    "VBT backlight PWM modulation frequency %u Hz, "
>  		    "active %s, min brightness %u, level %u, controller %u\n",
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index 748b0cd411fa..76f47ba3be45 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -326,6 +326,7 @@ struct intel_vbt_panel_data {
>  	struct {
>  		u16 pwm_freq_hz;
>  		u16 brightness_precision_bits;
> +		u16 hdr_dpcd_refresh_timeout;
>  		bool present;
>  		bool active_low_pwm;
>  		u8 min_brightness;	/* min_brightness/255 of max */
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index b77bd4565864..3734e7567230 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2293,10 +2293,15 @@ intel_edp_init_source_oui(struct intel_dp *intel_dp, bool careful)
>  
>  void intel_dp_wait_source_oui(struct intel_dp *intel_dp)
>  {
> +	struct intel_connector *connector = intel_dp->attached_connector;
>  	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>  
> -	drm_dbg_kms(&i915->drm, "Performing OUI wait\n");
> -	wait_remaining_ms_from_jiffies(intel_dp->last_oui_write, 30);
> +	drm_dbg_kms(&i915->drm, "[CONNECTOR:%d:%s] Performing OUI wait (%u ms)\n",
> +		    connector->base.base.id, connector->base.name,
> +		    connector->panel.vbt.backlight.hdr_dpcd_refresh_timeout);
> +
> +	wait_remaining_ms_from_jiffies(intel_dp->last_oui_write,
> +				       connector->panel.vbt.backlight.hdr_dpcd_refresh_timeout);
>  }
>  
>  /* If the device supports it, try to set the power state appropriately */

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat