[Intel-gfx] [PATCH] drm/i915/cnp: Display Wa #1179: WaHardHangonHotPlug

[Rodrigo Vivi]

"CNL PCH chance of hang when software accesses south display
registers after hotplug is enabled.
Workaround: Program 0xC2000 bits 11:8 = 0xF before enabling
south display hotplug detection."

"Workaround only needs to be applied to pre-production steppings
used in graphics capable SKUs, but it is easier to apply to
everything, and does not hurt."

v2: Moving from clock gating to right before enabling
    SHOTPLUG_CTL as it should be.

Suggested-by: Ben Widawsky <ben at bwidawsk.net>
Cc: Ben Widawsky <ben at bwidawsk.net>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/i915/i915_irq.c | 9 ++++++++-
 drivers/gpu/drm/i915/i915_reg.h | 2 ++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 4d0e8f76ed1a..901832a01d52 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -3218,7 +3218,14 @@ static void ibx_hpd_irq_setup(struct drm_i915_private *dev_priv)
 
 static void spt_hpd_detection_setup(struct drm_i915_private *dev_priv)
 {
-	u32 hotplug;
+	u32 val, hotplug;
+
+	/* Display WA #1179 WaHardHangonHotPlug: cnp */
+	if (HAS_PCH_CNP(dev_priv)) {
+		val = I915_READ(SOUTH_CHICKEN1) & ~CHASSIS_CLK_REQ_DURATION_MASK;
+		val |= CHASSIS_CLK_REQ_DURATION(0xf);
+		I915_WRITE(SOUTH_CHICKEN1, val);
+	}
 
 	/* Enable digital hotplug on the PCH */
 	hotplug = I915_READ(PCH_PORT_HOTPLUG);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index a8cb9c17e6df..2e1cdc099f14 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -7483,6 +7483,8 @@ enum {
 #define SOUTH_CHICKEN2		_MMIO(0xc2004)
 #define  FDI_MPHY_IOSFSB_RESET_STATUS	(1<<13)
 #define  FDI_MPHY_IOSFSB_RESET_CTL	(1<<12)
+#define  CHASSIS_CLK_REQ_DURATION_MASK	(0xf<<8)
+#define  CHASSIS_CLK_REQ_DURATION(x)	((x)<<8)
 #define  LPT_PWM_GRANULARITY		(1<<5)
 #define  DPLS_EDP_PPS_FIX_DIS		(1<<0)
 
-- 
2.13.5