[Intel-gfx] [PATCH] drm/i915: Restrict usage of live status check

[Chris Wilson]

On Thu, Mar 17, 2016 at 09:15:39PM +0530, Sharma, Shashank wrote:
> Regards
> Shashank
> 
> On 3/17/2016 6:34 PM, Ville Syrjälä wrote:
> >On Thu, Mar 17, 2016 at 01:29:25PM +0530, Shashank Sharma wrote:
> >>This patch restricts usage of live status check for HDMI detection.
> >>While testing certain (monitor + cable) combinations with various
> >>intel  platforms, it seems that live status register is not reliable
> >>on some older devices. So limit the live_status check from VLV onwards.
> >>
> >>This fixes a regression introduced in:
> >>	commit: 237ed86 "drm/i915: Check live status"
> >>	Author: Sonika Jindal <sonika.jindal at intel.com>
> >>	Date:   Tue Sep 15 09:44:20 2015 +0530
> >>
> >>Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
> >>---
> >>  drivers/gpu/drm/i915/intel_hdmi.c | 22 ++++++++++++++--------
> >>  1 file changed, 14 insertions(+), 8 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> >>index e2dab48..d24d18a 100644
> >>--- a/drivers/gpu/drm/i915/intel_hdmi.c
> >>+++ b/drivers/gpu/drm/i915/intel_hdmi.c
> >>@@ -1397,7 +1397,8 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
> >>  	enum drm_connector_status status;
> >>  	struct intel_hdmi *intel_hdmi = intel_attached_hdmi(connector);
> >>  	struct drm_i915_private *dev_priv = to_i915(connector->dev);
> >>-	bool live_status = false;
> >>+	struct drm_device *dev = connector->dev;
> >>+	bool live_status = true;
> >>  	unsigned int try;
> >>
> >>  	DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
> >>@@ -1405,16 +1406,21 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
> >>
> >>  	intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
> >>
> >>-	for (try = 0; !live_status && try < 9; try++) {
> >>-		if (try)
> >>-			msleep(10);
> >>-		live_status = intel_digital_port_connected(dev_priv,
> >>+	/*
> >>+	* Live status check for HDMI detection is not very
> >>+	* reliable on older platforms. So insist the live
> >>+	* status check for EDID read from VLV onwards.
> >>+	*/
> >>+	if (INTEL_INFO(dev)->gen >= 7 && !IS_IVYBRIDGE(dev)) {
> >>+		for (try = 0; !live_status && try < 9; try++) {
> >>+			if (try)
> >>+				msleep(10);
> >>+			live_status = intel_digital_port_connected(dev_priv,
> >>  				hdmi_to_dig_port(intel_hdmi));
> >>+		}
> >>+		DRM_DEBUG_KMS("Live status %s\n", live_status ? "up" : "down");
> >>  	}
> >>
> >>-	if (!live_status)
> >>-		DRM_DEBUG_KMS("Live status not up!");
> >>-
> >
> >As I said before, I think this whole thing could be solved with a simple
> >two-liner here:
> >
> >+	if (...)
> >+		live_status = true;
> >
> Yes I remember, and I replied on that already that why we would like
> to keep the live status check. In fact I would be ok to remove this
> check if you can suggest some other way of making this work for
> other operating systems/sw platforms.

The question is what is the safest approach for stable@ and for that
just doing as we historically did and ignore live_status makes the most
sense. Once the regressions have been rectified, then you can decide how
best to approach -next.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre