Re: [PATCH] drm/i915/glk: Add Quirk for GLK NUC HDMI port issues.

Clint Taylor <clinton.a.taylor@xxxxxxxxx> · Fri, 8 Jun 2018 08:48:37 -0700

On 06/08/2018 06:31 AM, Imre Deak wrote:
Hi Clint,

nice debugging!

On Thu, Jun 07, 2018 at 04:12:39PM -0700, clinton.a.taylor@xxxxxxxxx wrote:
From: Clint Taylor <clinton.a.taylor@xxxxxxxxx>

On GLK NUC platforms the HDMI retiming buffer needs additional disabled
time to correctly sync to a faster incoming signal.
When measured on a scope the highspeed lines of the HDMI clock turn
off for ~400uS during a normal resolution change.  The HDMI retimer on
the GLK NUC appears to require at least a full frame of quiet time
before a new faster clock can be correctly sync'd.
The worst case scenario appears to be 23.98Hz modes which requires a
wait of 41.25ms. Add a quirk to the driver for GLK NUC that waits
42ms.
Just to understand better the failure mode: IIUC without the WA the HDMI
clock line is inactive for ~400us when switching modes (which would
depend on kernel timing) and the retimer chip needs at least 42ms idle
time at least when switching to certain modes.
If switching from 30Hz to 50/60Hz you would only need a delay of 34ms, 
but I chose to keep the quirk simple and use the worst case (23.98Hz) 
delay of 42ms.

Is there a way to recover the chip from the bad state? By doing a new
off/on modeset with enough idle time, or resetting the chip?
Just an off/on mode set with enough delay will bring the chip out of the 
bad state.

-Clint

--Imre

Cc: Imre Deak <imre.deak@xxxxxxxxx>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105887
Signed-off-by: Clint Taylor <clinton.a.taylor@xxxxxxxxx>
---
  drivers/gpu/drm/i915/i915_drv.h      |  1 +
  drivers/gpu/drm/i915/intel_ddi.c     |  8 ++++++++
  drivers/gpu/drm/i915/intel_display.c | 14 ++++++++++++++
  3 files changed, 23 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index c407366..628491d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -645,6 +645,7 @@ enum intel_sbi_destination {
  #define QUIRK_BACKLIGHT_PRESENT (1<<3)
  #define QUIRK_PIN_SWIZZLED_PAGES (1<<5)
  #define QUIRK_INCREASE_T12_DELAY (1<<6)
+#define QUIRK_INCREASE_DDI_DISABLED_TIME (1<<7)
  
  struct intel_fbdev;
  struct intel_fbc_work;
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index b344e0f..61b41c3 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1784,6 +1784,9 @@ void intel_ddi_enable_transcoder_func(const struct intel_crtc_state *crtc_state)
  	I915_WRITE(TRANS_DDI_FUNC_CTL(cpu_transcoder), temp);
  }
  
+/* Quirk time computed based on 24fps frame time of 41.25ms */
+#define DDI_DISABLED_QUIRK_TIME 42
+
  void intel_ddi_disable_transcoder_func(struct drm_i915_private *dev_priv,
  				       enum transcoder cpu_transcoder)
  {
@@ -1793,6 +1796,11 @@ void intel_ddi_disable_transcoder_func(struct drm_i915_private *dev_priv,
  	val &= ~(TRANS_DDI_FUNC_ENABLE | TRANS_DDI_PORT_MASK | TRANS_DDI_DP_VC_PAYLOAD_ALLOC);
  	val |= TRANS_DDI_PORT_NONE;
  	I915_WRITE(reg, val);
+
+	if (dev_priv->quirks & QUIRK_INCREASE_DDI_DISABLED_TIME) {
+		msleep(DDI_DISABLED_QUIRK_TIME);
+		DRM_DEBUG_KMS("Quirk Increase DDI disabled time\n");
+	}
  }
  
  int intel_ddi_toggle_hdcp_signalling(struct intel_encoder *intel_encoder,
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index ed29219..0d07c37 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -14740,6 +14740,17 @@ static void quirk_increase_t12_delay(struct drm_device *dev)
  	DRM_INFO("Applying T12 delay quirk\n");
  }
  
+/* GeminiLake NUC HDMI outputs require additional off time
+ * this allows the onboard retimer to correctly sync to signal
+ */
+static void quirk_increase_ddi_disabled_time(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = to_i915(dev);
+
+	dev_priv->quirks |= QUIRK_INCREASE_DDI_DISABLED_TIME;
+	DRM_INFO("Applying Increase DDI Disabled quirk\n");
+}
+
  struct intel_quirk {
  	int device;
  	int subsystem_vendor;
@@ -14826,6 +14837,9 @@ static int intel_dmi_reverse_brightness(const struct dmi_system_id *id)
  
  	/* Toshiba Satellite P50-C-18C */
  	{ 0x191B, 0x1179, 0xF840, quirk_increase_t12_delay },
+
+	/* GeminiLake NUC */
+	{ 0x3185, 0x8086, 0x2072, quirk_increase_ddi_disabled_time },
  };
  
  static void intel_init_quirks(struct drm_device *dev)
--
1.9.1


_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/intel-gfx







