> -----Original Message----- > From: Kandpal, Suraj <suraj.kandpal@xxxxxxxxx> > Sent: Monday, July 17, 2023 2:54 PM > To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx > Cc: Kandpal, Suraj <suraj.kandpal@xxxxxxxxx>; Shankar, Uma > <uma.shankar@xxxxxxxxx>; Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> > 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.shankar@xxxxxxxxx> > Bspec: 68970 > > Cc: Uma Shankar <uma.shankar@xxxxxxxxx> > Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> > Signed-off-by: Suraj Kandpal <suraj.kandpal@xxxxxxxxx> > --- > 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
