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

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Mar 28, 2023 at 04:09:33PM -0400, Lyude Paul wrote:
> BTW - I just started catching up with my email, is this waiting on me or was
> someone else able to review it?

commit fe82b93fc101 ("drm/i915: Get HDR DPCD refresh timeout from VBT")

> 
> 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

-- 
Ville Syrjälä
Intel