From 5100e27733f358419466ee40c5143f6786ecbe3c Mon Sep 17 00:00:00 2001
From: Suraj Kandpal <suraj.kandpal@intel.com>
Date: Thu, 20 Jul 2023 16:16:24 +0530
Subject: drm/i915/hotplug: Reduce SHPD_FILTER to 250us
Git-commit: 4948738e296c75de57e0c4a8e8ead1ff2c03fe00
Patch-mainline: v6.6-rc1
References: jsc#PED-3527 jsc#PED-5475 jsc#PED-6068 jsc#PED-6070 jsc#PED-6116 jsc#PED-6120 jsc#PED-5065 jsc#PED-5477 jsc#PED-5511 jsc#PED-6041 jsc#PED-6069 jsc#PED-6071
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.
Bspec: 68970
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Suggested-by: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230720104624.3063544-1-suraj.kandpal@intel.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
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 7a4f462e8b70..4f94a0367cb9 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -4917,6 +4917,7 @@
#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
--
2.43.0