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

[Ville Syrjälä]

On Fri, Mar 18, 2016 at 08:51:29AM +0530, Sharma, Shashank wrote:
> Regards
> Shashank
> 
> On 3/17/2016 10:17 PM, Ville Syrjälä wrote:
> > On Thu, Mar 17, 2016 at 10:03:04PM +0530, Sharma, Shashank wrote:
> >> Hey Chris,
> >> I added comments for both Ville and you, please help me to understand this.
> >>
> >> Regards
> >> Shashank
> >>
> >> On 3/17/2016 9:51 PM, Ville Syrjälä wrote:
> >>> On Thu, Mar 17, 2016 at 09:35:30PM +0530, Sharma, Shashank wrote:
> >>>> Regards
> >>>> Shashank
> >>>>
> >>>> On 3/17/2016 9:31 PM, Ville Syrjälä wrote:
> >>>>> 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.
> >>>>>
> >>>>> My two liner would keep the check.
> >>>>>
> >>>> Sorry, I might have not understood you properly.
> >>>> Do you mean:
> >>>> 	if (INTEL_INFO(dev)->gen < 7 && IS_IVYBRIDGE(dev)) {
> >>>> 		live_status = true;
> >>>> 	} else {
> >>>> 		do the same looping for retry;
> >>>> 	}
> >>>
> >>> No, I mean
> >>>
> >>> {
> >>> 	...
> >>> 	do loop;
> >>>
> >>> 	if (!live_status)
> >>> 		DRM_DEBUG_KMS("Live status not up!");
> >>>
> >>> +	if (don't trust live status)
> >>> +		live_status = true;
> >>> 	
> >>> 	intel_hdmi_unset_edid();
> >>> 	
> >>> 	if (intel_hdmi_set_edid(live_status)) {
> >>> 	...
> >>> }
> >>>
> >>>
> >> In fact, this is what I have done.
> >> If you see the change in this patch,
> >> 	/* Lets make live status true for < VLV platforms */
> >> 	bool live_status = true;
> >>
> >> 	blah....
> >> 	blah....
> >>
> >> 	/* Check live status only for newer platforms */
> >> 	if (this is VLV or later platforms) {
> >> 		live_status = read_real_live_status();
> >> 	}
> >> 	intel_hdmi_unset_edid();
> >> 	intel_hdmi_set_edid(live_status);
> >>
> >> Now, my question is, do you want to remove live_status check for VLV and
> >> other platforms too ? or this is good enough ?
> >
> > No, I'm objecting to changing the entire code when you could just add
> > two lines. Also my way has the extra benefit that we keep the live
> > status check mostly working on these presumed "broken" platforms.
> >
> > So the only difference to the current situation is that we would still
> > attempt the EDID read even if live_status came out as false, but thanks
> > to the extra delay from the live status polling we would hopefully
> > avoid spurious detection results since the EDID read gets delayed a bit.
> >
> Ok, thanks for this suggestion. I will do the change.
> I was thinking of adding a warning, if we are going to read the EDID 
> without live status being set, sounds ok ?

Yeah, adding a debug message might be prudent.

> 
> >> 	
> >>>>
> >>>>>>>>      	intel_hdmi_unset_edid(connector);
> >>>>>>>>
> >>>>>>>>      	if (intel_hdmi_set_edid(connector, live_status)) {
> >>>>>>>> --
> >>>>>>>> 1.9.1
> >>>>>>>
> >>>>>
> >>>
> >

-- 
Ville Syrjälä
Intel OTC