Re: [PATCH v4] drm/i915/display: Panel Replay BW optimization for DP2.0 tunneling

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

On Fri, 27 Feb 2026, Animesh Manna <animesh.manna@intel.com> wrote:
> Unused bandwidth can be used by external display agents for Panel Replay
> enabled DP panel during idleness with link on. Enable source to replace
> dummy data from the display with data from another agent by programming
> TRANS_DP2_CTL [Panel Replay Tunneling Enable].
>
> v2:
> - Enable pr bw optimization along with panel replay enable. [Jani]
>
> v3:
> - Write TRANS_DP2_CTL once for both bw optimization and panel replay
> enable. [Jani]
>
> v4:
> - Read DPCD once in init() and store in panel_replay_caps. [Jouni]
>
> Bspec: 68920
> Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
> Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> ---
>  .../gpu/drm/i915/display/intel_display_regs.h |  1 +
>  .../drm/i915/display/intel_display_types.h    |  1 +
>  drivers/gpu/drm/i915/display/intel_dp.c       |  1 +
>  drivers/gpu/drm/i915/display/intel_psr.c      | 30 +++++++++++++++++--
>  4 files changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_regs.h b/drivers/gpu/drm/i915/display/intel_display_regs.h
> index 49e2a9e3ee0e..71411b26e918 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_regs.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_regs.h
> @@ -2265,6 +2265,7 @@
>  #define TRANS_DP2_CTL(trans)			_MMIO_TRANS(trans, _TRANS_DP2_CTL_A, _TRANS_DP2_CTL_B)
>  #define  TRANS_DP2_128B132B_CHANNEL_CODING	REG_BIT(31)
>  #define  TRANS_DP2_PANEL_REPLAY_ENABLE		REG_BIT(30)
> +#define  TRANS_DP2_PR_TUNNELING_ENABLE		REG_BIT(26)
>  #define  TRANS_DP2_DEBUG_ENABLE			REG_BIT(23)
>  
>  #define _TRANS_DP2_VFREQHIGH_A			0x600a4
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index e8e4af03a6a6..0b30f9085afb 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -576,6 +576,7 @@ struct intel_connector {
>  
>  			bool support;
>  			bool su_support;
> +			bool optimization_support;
>  			enum intel_panel_replay_dsc_support dsc_support;
>  
>  			u16 su_w_granularity;
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 025e906b63a9..f35aafe1e86f 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -6250,6 +6250,7 @@ intel_dp_detect(struct drm_connector *_connector,
>  		intel_dp->psr.sink_panel_replay_support = false;
>  		connector->dp.panel_replay_caps.support = false;
>  		connector->dp.panel_replay_caps.su_support = false;
> +		connector->dp.panel_replay_caps.optimization_support = false;
>  		connector->dp.panel_replay_caps.dsc_support =
>  			INTEL_DP_PANEL_REPLAY_DSC_NOT_SUPPORTED;
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> index 5bea2eda744b..dc3e4d8885fa 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -43,6 +43,7 @@
>  #include "intel_dmc.h"
>  #include "intel_dp.h"
>  #include "intel_dp_aux.h"
> +#include "intel_dp_tunnel.h"
>  #include "intel_dsb.h"
>  #include "intel_frontbuffer.h"
>  #include "intel_hdmi.h"
> @@ -603,6 +604,7 @@ static void _panel_replay_init_dpcd(struct intel_dp *intel_dp, struct intel_conn
>  {
>  	struct intel_display *display = to_intel_display(intel_dp);
>  	int ret;
> +	u8 val;
>  
>  	/* TODO: Enable Panel Replay on MST once it's properly implemented. */
>  	if (intel_dp->mst_detect == DRM_DP_MST)
> @@ -650,6 +652,10 @@ static void _panel_replay_init_dpcd(struct intel_dp *intel_dp, struct intel_conn
>  		    connector->dp.panel_replay_caps.su_support ?
>  		    "selective_update " : "",
>  		    panel_replay_dsc_support_str(connector->dp.panel_replay_caps.dsc_support));
> +
> +	drm_dp_dpcd_readb(&intel_dp->aux, DP_TUNNELING_CAPABILITIES, &val);

drm_dp_dpcd_read_byte() is preferred over drm_dp_dpcd_readb().

> +	connector->dp.panel_replay_caps.optimization_support =
> +		(val & DP_PANEL_REPLAY_OPTIMIZATION_SUPPORT) ? true : false;

Drive-by comment, this can be simplified to just:

	connector->dp.panel_replay_caps.optimization_support = val & DP_PANEL_REPLAY_OPTIMIZATION_SUPPORT;

>  }
>  
>  static void _psr_init_dpcd(struct intel_dp *intel_dp, struct intel_connector *connector)
> @@ -1022,11 +1028,29 @@ static u8 frames_before_su_entry(struct intel_dp *intel_dp)
>  	return frames_before_su_entry;
>  }
>  
> +static bool intel_psr_allow_pr_bw_optimization(struct intel_dp *intel_dp)
> +{
> +	struct intel_display *display = to_intel_display(intel_dp);
> +	struct intel_connector *connector = intel_dp->attached_connector;
> +
> +	if (DISPLAY_VER(display) < 35)
> +		return false;
> +
> +	if (!intel_dp_tunnel_bw_alloc_is_enabled(intel_dp))
> +		return false;
> +
> +	if (!(connector->dp.panel_replay_caps.optimization_support))

Excess parenthesis.

> +		return false;
> +
> +	return true;
> +}
> +
>  static void dg2_activate_panel_replay(struct intel_dp *intel_dp)
>  {
>  	struct intel_display *display = to_intel_display(intel_dp);
>  	struct intel_psr *psr = &intel_dp->psr;
>  	enum transcoder cpu_transcoder = intel_dp->psr.transcoder;
> +	u32 dp2_ctl_val = TRANS_DP2_PANEL_REPLAY_ENABLE;
>  
>  	if (intel_dp_is_edp(intel_dp) && psr->sel_update_enabled) {
>  		u32 val = psr->su_region_et_enabled ?
> @@ -1039,12 +1063,14 @@ static void dg2_activate_panel_replay(struct intel_dp *intel_dp)
>  			       val);
>  	}
>  
> +	if (!intel_dp_is_edp(intel_dp) && intel_psr_allow_pr_bw_optimization(intel_dp))
> +		dp2_ctl_val |= TRANS_DP2_PR_TUNNELING_ENABLE;
> +
>  	intel_de_rmw(display,
>  		     PSR2_MAN_TRK_CTL(display, intel_dp->psr.transcoder),
>  		     0, ADLP_PSR2_MAN_TRK_CTL_SF_CONTINUOS_FULL_FRAME);
>  
> -	intel_de_rmw(display, TRANS_DP2_CTL(intel_dp->psr.transcoder), 0,
> -		     TRANS_DP2_PANEL_REPLAY_ENABLE);
> +	intel_de_rmw(display, TRANS_DP2_CTL(intel_dp->psr.transcoder), 0, dp2_ctl_val);
>  }
>  
>  static void hsw_activate_psr2(struct intel_dp *intel_dp)

-- 
Jani Nikula, Intel