Re: [PATCH v7 2/3] drm/i915/display: Panel Replay BW optimization for DP2.0 tunneling

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Thu, 2026-03-12 at 10:30 +0530, Animesh Manna 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]
> 
> v5:
> - Avoid reading DPCD for edp. [Jouni]
> - Use drm_dp_dpcd_read_byte() and some cosmetic changes. [Jani]
> 
> v6:
> - Extend the corresponding interface defined in drm_dp_tunnel.c
> to query the Panel Replay optimization capability. [Imre]
> 
> 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 +
>  drivers/gpu/drm/i915/display/intel_psr.c      | 24
> +++++++++++++++++--
>  2 files changed, 23 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 4746e9ebd920..dada8dc27ea4 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_regs.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_regs.h
> @@ -2263,6 +2263,7 @@
>  #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_psr.c
> b/drivers/gpu/drm/i915/display/intel_psr.c
> index 5041a5a138d1..632527ede29f 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -44,6 +44,7 @@
>  #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"
> @@ -1023,11 +1024,28 @@ 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);
> +
> +	if (DISPLAY_VER(display) < 35)
> +		return false;

This is not necessary if you check it already at compute config.

> +
> +	if (!intel_dp_tunnel_bw_alloc_is_enabled(intel_dp))
> +		return false;
> +
> +	if (!intel_dp_tunnel_pr_optimization_supported(intel_dp))
> +		return false;

You should move this patch after patch 3. Then you can drop this check.

> +
> +	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 ?
> @@ -1040,12 +1058,14 @@ 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;

If you do modification I commented above you could just check
intel_dp_tunnel_bw_alloc_is_enabled here. No need to add
intel_psr_allow_pr_bw_optimization helper.

BR,

Jouni Högander

>  		     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)