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

[Sharma, Shashank]

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