Re: [PATCH] drm/i915/vrr: Program EMP_AS_SDP_TL for DP AS SDP

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

On Tue, 29 Apr 2025, Ankit Nautiyal <ankit.k.nautiyal@intel.com> wrote:
> The register EMP_AS_SDP_TL (MTL) was introduced for configuring the
> double buffering point and transmission line for
> HDMI Video Timing Extended Metadata Packet (VTEMP) for VRR.
> This was also intended to be configured for DP to HDMI2.1 PCON to
> support VRR.
>
> From BMG and LNL+ onwards, this register was extended to Display Port
> Adaptive Sync SDP to have a common register to configure double
> buffering point and transmission line for both HDMI and DP VRR related
> packets.
>
> Currently, we do not support VRR for either native HDMI or via PCON.
> However we need to configure this for DP SDP case. As per the spec,
> program the register to set Vsync start as the double buffering point
> for DP AS SDP.
>
> Bspec:70984, 71197
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_vrr.c      | 20 +++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_vrr_regs.h |  6 ++++++
>  2 files changed, 26 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
> index c6565baf815a..2447bdfde5af 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> @@ -576,6 +576,22 @@ bool intel_vrr_always_use_vrr_tg(struct intel_display *display)
>  	return false;
>  }
>  
> +static
> +void intel_vrr_set_emp_as_sdp_tl(const struct intel_crtc_state *crtc_state)

How do you pronounce that function name?

BR,
Jani.

> +{
> +	struct intel_display *display = to_intel_display(crtc_state);
> +	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
> +
> +	/*
> +	 * For BMG and LNL+ onwards the EMP_AS_SDP_TL is used for programming
> +	 * double buffering point and transmission line for Adaptive Sync SDP.
> +	 */
> +	if (DISPLAY_VERx100(display) == 1401 || DISPLAY_VER(display) >= 20)
> +		intel_de_write(display,
> +			       EMP_AS_SDP_TL(display, cpu_transcoder),
> +			       EMP_AS_SDP_DB_TL(crtc_state->vrr.vsync_start));
> +}
> +
>  void intel_vrr_enable(const struct intel_crtc_state *crtc_state)
>  {
>  	struct intel_display *display = to_intel_display(crtc_state);
> @@ -595,6 +611,8 @@ void intel_vrr_enable(const struct intel_crtc_state *crtc_state)
>  		       TRANS_PUSH_EN);
>  
>  	if (!intel_vrr_always_use_vrr_tg(display)) {
> +		intel_vrr_set_emp_as_sdp_tl(crtc_state);
> +
>  		if (crtc_state->cmrr.enable) {
>  			intel_de_write(display, TRANS_VRR_CTL(display, cpu_transcoder),
>  				       VRR_CTL_VRR_ENABLE | VRR_CTL_CMRR_ENABLE |
> @@ -646,6 +664,8 @@ void intel_vrr_transcoder_enable(const struct intel_crtc_state *crtc_state)
>  	intel_de_write(display, TRANS_PUSH(display, cpu_transcoder),
>  		       TRANS_PUSH_EN);
>  
> +	intel_vrr_set_emp_as_sdp_tl(crtc_state);
> +
>  	intel_de_write(display, TRANS_VRR_CTL(display, cpu_transcoder),
>  		       VRR_CTL_VRR_ENABLE | trans_vrr_ctl(crtc_state));
>  }
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr_regs.h b/drivers/gpu/drm/i915/display/intel_vrr_regs.h
> index 6ed0e0dc97e7..d2af1b6710bf 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr_regs.h
> +++ b/drivers/gpu/drm/i915/display/intel_vrr_regs.h
> @@ -108,6 +108,12 @@
>  #define VRR_VSYNC_START_MASK			REG_GENMASK(12, 0)
>  #define VRR_VSYNC_START(vsync_start)		REG_FIELD_PREP(VRR_VSYNC_START_MASK, (vsync_start))
>  
> +/* Common register for HDMI VTEMP and DP AS SDP */
> +#define _EMP_AS_SDP_TL_A			0x60204
> +#define EMP_AS_SDP_DB_TL_MASK			REG_GENMASK(12, 0)
> +#define EMP_AS_SDP_TL(dev_priv, trans)		_MMIO_TRANS2(dev_priv, trans, _EMP_AS_SDP_TL_A)
> +#define EMP_AS_SDP_DB_TL(db_transmit_line)	REG_FIELD_PREP(EMP_AS_SDP_DB_TL_MASK, (db_transmit_line))
> +
>  /*CMRR Registers*/
>  
>  #define _TRANS_CMRR_M_LO_A			0x604F0

-- 
Jani Nikula, Intel