[Intel-gfx] [PATCH v2] drm/i915: Correct max delay for HDMI hotplug live status checking

Wang, Gary C gary.c.wang at intel.com
Thu Dec 17 17:21:42 PST 2015

For BSW platform, 
it seems 10ms delay of hot-plug detecting is not enough and to cause high fail-rate on old HDMI monitor, and I would like correct it. 

Then user needs to wait screen blank for 2 mins or re-plugin cable (impact to user experience).

Thanks for your review.


-----Original Message-----
From: Wang, Gary C 
Sent: Tuesday, December 15, 2015 12:41 PM
To: intel-gfx at lists.freedesktop.org
Cc: Wang, Gary C <gary.c.wang at intel.com>; Jani Nikula <jani.nikula at linux.intel.com>; Daniel Vetter <daniel at ffwll.ch>; Hindman, Gavin <gavin.hindman at intel.com>; Jindal, Sonika <sonika.jindal at intel.com>; Sharma, Shashank <shashank.sharma at intel.com>
Subject: [PATCH v2] drm/i915: Correct max delay for HDMI hotplug live status checking

The total delay of HDMI hotplug detecting with 30ms have already been split into a resolution of 3 retries of 10ms each, for the worst cases. But it still suffered from only waiting 10ms at most in intel_hdmi_detect(). This patch corrects it by reading hotplug status with 4 times at most for 30ms delay.

- straight up to loop execution for more clear in code readability
- mdelay will replace with msleep by Daniel's new patch

	drm/i915: mdelay(10) considered harmful

- suggest to re-evaluate try times for being compatible to old HDMI monitor

Reviewed-by: Cooper Chiou <cooper.chiou at intel.com>
Tested-by: Gary Wang <gary.c.wang at intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Gavin Hindman <gavin.hindman at intel.com>
Cc: Sonika Jindal <sonika.jindal at intel.com>
Cc: Shashank Sharma <shashank.sharma at intel.com>
Signed-off-by: Gary Wang <gary.c.wang at intel.com>
 drivers/gpu/drm/i915/intel_hdmi.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)  mode change 100644 => 100755 drivers/gpu/drm/i915/intel_hdmi.c

diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
old mode 100644
new mode 100755
index 6825543..912d6c3
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -1387,17 +1387,18 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
 	struct intel_hdmi *intel_hdmi = intel_attached_hdmi(connector);
 	struct drm_i915_private *dev_priv = to_i915(connector->dev);
 	bool live_status = false;
-	unsigned int retry = 3;
+	unsigned int try;
 		      connector->base.id, connector->name);
 	intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
-	while (!live_status && --retry) {
+	for (try = 0; !live_status && try < 4; try++) {
+		if (try)
+			mdelay(10);
 		live_status = intel_digital_port_connected(dev_priv,
-		mdelay(10);
 	if (!live_status)

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