> -----Original Message-----
> From: Intel-gfx <intel-gfx-boun...@lists.freedesktop.org> On Behalf Of
> Shankar,
> Uma
> Sent: Thursday, July 20, 2023 3:41 PM
> To: Kandpal, Suraj <suraj.kand...@intel.com>; intel-gfx@lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH] drm/i915/hotplug: Reduce SHPD_FILTER to 250us
>
>
>
> > -----Original Message-----
> > From: Kandpal, Suraj <suraj.kand...@intel.com>
> > Sent: Monday, July 17, 2023 2:54 PM
> > To: intel-gfx@lists.freedesktop.org
> > Cc: Kandpal, Suraj <suraj.kand...@intel.com>; Shankar, Uma
> > <uma.shan...@intel.com>; Ville Syrjala <ville.syrj...@linux.intel.com>
> > Subject: [PATCH] drm/i915/hotplug: Reduce SHPD_FILTER to 250us
> >
> > On TGP, the RTC (always running) was reduced from 3MHz to 32KHz.
> > As a result of this change, when HPD active going low pulse or HPD IRQ
> > is presented and the refclk (19.2MHz) is not toggling already
> > toggling, there is a 60 to 90us synchronization delay which
> > effectively reduces the duration of the IRQ pulse to less than the
> > programmed
> 500us filter value and the hot plug interrupt is NOT registered.
> > Solution was to Reduce SHPD_FILTER to 250us for ADL and above.
> > This solution was derived when the below patch was floated.
> > [1]https://patchwork.freedesktop.org/patch/532187
> > and after some internal discussion Ville's suggestion made sense.
>
> Looks Good to me. Just add also a Suggested-By tag mentioning Ville.
> Reviewed-by: Uma Shankar <uma.shan...@intel.com>
Pushed to drm-intel-next. Thanks for the change.
Regards,
Uma Shankar
> > Bspec: 68970
> >
> > Cc: Uma Shankar <uma.shan...@intel.com>
> > Cc: Ville Syrjala <ville.syrj...@linux.intel.com>
> > Signed-off-by: Suraj Kandpal <suraj.kand...@intel.com>
> > ---
> > drivers/gpu/drm/i915/display/intel_hotplug_irq.c | 4 +++-
> > drivers/gpu/drm/i915/i915_reg.h | 1 +
> > 2 files changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_hotplug_irq.c
> > b/drivers/gpu/drm/i915/display/intel_hotplug_irq.c
> > index f95fa793fabb..95a7ea94f417 100644
> > --- a/drivers/gpu/drm/i915/display/intel_hotplug_irq.c
> > +++ b/drivers/gpu/drm/i915/display/intel_hotplug_irq.c
> > @@ -842,6 +842,8 @@ static void icp_hpd_irq_setup(struct
> > drm_i915_private
> > *dev_priv)
> >
> > if (INTEL_PCH_TYPE(dev_priv) <= PCH_TGP)
> > intel_uncore_write(&dev_priv->uncore, SHPD_FILTER_CNT,
> > SHPD_FILTER_CNT_500_ADJ);
> > + else
> > + intel_uncore_write(&dev_priv->uncore, SHPD_FILTER_CNT,
> > +SHPD_FILTER_CNT_250);
> >
> > ibx_display_interrupt_update(dev_priv, hotplug_irqs, enabled_irqs);
> >
> > @@ -1049,7 +1051,7 @@ static void mtp_hpd_irq_setup(struct
> > drm_i915_private
> > *i915)
> > enabled_irqs = intel_hpd_enabled_irqs(i915,
> > i915->display.hotplug.pch_hpd);
> > hotplug_irqs = intel_hpd_hotplug_irqs(i915,
> > i915->display.hotplug.pch_hpd);
> >
> > - intel_de_write(i915, SHPD_FILTER_CNT, SHPD_FILTER_CNT_500_ADJ);
> > + intel_de_write(i915, SHPD_FILTER_CNT, SHPD_FILTER_CNT_250);
> >
> > mtp_hpd_invert(i915);
> > ibx_display_interrupt_update(i915, hotplug_irqs, enabled_irqs); diff
> > --git a/drivers/gpu/drm/i915/i915_reg.h
> > b/drivers/gpu/drm/i915/i915_reg.h index dcf64e32cd54..aefad14ab27a
> > 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -4939,6 +4939,7 @@
> >
> > #define SHPD_FILTER_CNT _MMIO(0xc4038)
> > #define SHPD_FILTER_CNT_500_ADJ 0x001D9
> > +#define SHPD_FILTER_CNT_250 0x000F8
> >
> > #define _PCH_DPLL_A 0xc6014
> > #define _PCH_DPLL_B 0xc6018
> > --
> > 2.25.1
