> -----Original Message-----
> From: Ville Syrjälä <[email protected]>
> Sent: Tuesday, February 24, 2026 1:43 PM
> To: Shankar, Uma <[email protected]>
> Cc: [email protected]; [email protected]; Golani,
> Mitulkumar Ajitkumar <[email protected]>; Nautiyal, Ankit
> K
> <[email protected]>
> Subject: Re: [PATCH] drm/i915/display: Enable AS SDP Skip Frames
>
> On Tue, Feb 24, 2026 at 02:37:07AM +0530, Uma Shankar wrote:
> > Hardware provides mechanism to skip AS SDP for programmed number of
> > frames. Enable the same to drive to 1Hz if hardware supports it.
> >
> > Signed-off-by: Uma Shankar <[email protected]>
> > ---
> > drivers/gpu/drm/i915/display/intel_alpm.c | 3 +++
> > drivers/gpu/drm/i915/display/intel_psr_regs.h | 2 ++
> > 2 files changed, 5 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c
> > b/drivers/gpu/drm/i915/display/intel_alpm.c
> > index b3334bc4d0f9..76a8919cdba2 100644
> > --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> > +++ b/drivers/gpu/drm/i915/display/intel_alpm.c
> > @@ -395,6 +395,9 @@ static void lnl_alpm_configure(struct intel_dp
> > *intel_dp,
> > if (crtc_state->disable_as_sdp_when_pr_active)
> > pr_alpm_ctl |=
> PR_ALPM_CTL_AS_SDP_TRANSMISSION_IN_ACTIVE_DISABLE;
> >
> > + if (DISPLAY_VER(display) >= 35)
> > + pr_alpm_ctl |=
> PR_ALPM_CTL_ASSDP_SKIP_FRAMES(32);
>
> Where did that magic 32 frames come from?
Sorry missed to call out, this is just a default value to test on hardware.
Will update it and make it truly programmable.
> This whole thing seems to involve a lot of details (Bspec:75539) that someone
> needs to think through.
>
> There are also some things in the DP 2.1a spec (eg. 2.18.8.1.1 Enabling
> Autonomous Sink Device Refresh Rate Timing) that seem relevant for this stuff.
> Sadly the bspec page makes no mention of any of this :/
I will try to add the relevant restrictions and DC3Co dependencies. Need to
check on hardware
to cover all corner cases.
Thanks Ville for pointing out the DP spec link relevant to this. Will refer and
get back.
Regards,
Uma Shankar
> > +
> > intel_de_write(display, PR_ALPM_CTL(display,
> cpu_transcoder),
> > pr_alpm_ctl);
> > }
> > diff --git a/drivers/gpu/drm/i915/display/intel_psr_regs.h
> > b/drivers/gpu/drm/i915/display/intel_psr_regs.h
> > index 8afbf5a38335..8c35df795955 100644
> > --- a/drivers/gpu/drm/i915/display/intel_psr_regs.h
> > +++ b/drivers/gpu/drm/i915/display/intel_psr_regs.h
> > @@ -268,6 +268,8 @@
> >
> > #define _PR_ALPM_CTL_A 0x60948
> > #define PR_ALPM_CTL(dev_priv, tran) _MMIO_TRANS2(dev_priv, tran,
> _PR_ALPM_CTL_A)
> > +#define PR_ALPM_CTL_ASSDP_SKIP_FRAMES_MASK
> REG_GENMASK(27, 16)
> > +#define PR_ALPM_CTL_ASSDP_SKIP_FRAMES(val)
> REG_FIELD_PREP(PR_ALPM_CTL_ASSDP_SKIP_FRAMES_MASK, val)
> > #define PR_ALPM_CTL_ALLOW_LINK_OFF_BETWEEN_AS_SDP_AND_SU
> BIT(6)
> > #define PR_ALPM_CTL_RFB_UPDATE_CONTROL
> BIT(5)
> > #define PR_ALPM_CTL_AS_SDP_TRANSMISSION_IN_ACTIVE_DISABLE
> BIT(4)
> > --
> > 2.50.1
>
> --
> Ville Syrjälä
> Intel
