[PATCH] drm/i915/psr: Do not read PSR2_SU_STATUS on AlderLake and onwards

[Kahola, Mika]

> -----Original Message-----
> From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of Jouni
> Högander
> Sent: Wednesday, 16 April 2025 12.36
> To: intel-gfx at lists.freedesktop.org; intel-xe at lists.freedesktop.org
> Cc: Hogander, Jouni <jouni.hogander at intel.com>
> Subject: [PATCH] drm/i915/psr: Do not read PSR2_SU_STATUS on AlderLake and
> onwards
> 
> Bspec comment on PSR2_SU_STATUS:
> 
> "This register has been tied-off since DG2/ADL-P (it returns zeros only) and it has
> been removed on Xe2_LPD."
> 
> Bspec: 69889

Reviewed-by: Mika Kahola <mika.kahola at intel.com>

> Signed-off-by: Jouni Högander <jouni.hogander at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_psr.c | 34 ++++++++++++++----------
>  1 file changed, 20 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> b/drivers/gpu/drm/i915/display/intel_psr.c
> index 6d6ef6681e3fc..0ec73c2f4336f 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -3874,24 +3874,30 @@ static int intel_psr_status(struct seq_file *m, struct
> intel_dp *intel_dp)
>  		int frame;
> 
>  		/*
> -		 * Reading all 3 registers before hand to minimize crossing a
> -		 * frame boundary between register reads
> +		 * PSR2_SU_STATUS register has been tied-off since DG2/ADL-P
> +		 * (it returns zeros only) and it has been removed on Xe2_LPD.
>  		 */
> -		for (frame = 0; frame < PSR2_SU_STATUS_FRAMES; frame += 3) {
> -			val = intel_de_read(display,
> -					    PSR2_SU_STATUS(display,
> cpu_transcoder, frame));
> -			su_frames_val[frame / 3] = val;
> -		}
> +		if (DISPLAY_VER(display) >= 13) {
> +			/*
> +			 * Reading all 3 registers before hand to minimize
> crossing a
> +			 * frame boundary between register reads
> +			 */
> +			for (frame = 0; frame < PSR2_SU_STATUS_FRAMES;
> frame += 3) {
> +				val = intel_de_read(display,
> +						    PSR2_SU_STATUS(display,
> cpu_transcoder, frame));
> +				su_frames_val[frame / 3] = val;
> +			}
> 
> -		seq_puts(m, "Frame:\tPSR2 SU blocks:\n");
> +			seq_puts(m, "Frame:\tPSR2 SU blocks:\n");
> 
> -		for (frame = 0; frame < PSR2_SU_STATUS_FRAMES; frame++) {
> -			u32 su_blocks;
> +			for (frame = 0; frame < PSR2_SU_STATUS_FRAMES;
> frame++) {
> +				u32 su_blocks;
> 
> -			su_blocks = su_frames_val[frame / 3] &
> -				    PSR2_SU_STATUS_MASK(frame);
> -			su_blocks = su_blocks >>
> PSR2_SU_STATUS_SHIFT(frame);
> -			seq_printf(m, "%d\t%d\n", frame, su_blocks);
> +				su_blocks = su_frames_val[frame / 3] &
> +					PSR2_SU_STATUS_MASK(frame);
> +				su_blocks = su_blocks >>
> PSR2_SU_STATUS_SHIFT(frame);
> +				seq_printf(m, "%d\t%d\n", frame, su_blocks);
> +			}
>  		}
> 
>  		seq_printf(m, "PSR2 selective fetch: %s\n",
> --
> 2.43.0