[Intel-gfx] [PATCH v2] drm/i915: Restrict usage of live status check

[Sharma, Shashank]

Hi Ville,
Please ignore my last email.

I think I finally got it what you exactly suggested.
Please check another patch sent by me:
	drm/i915: Fake HDMI live status

There are two versions of this patch:
	v1: fake live_status = true for all platforms.
	v2: fake live_status = true only for (< gen7 and IVB platforms).

please suggest which one will you prefer to go as a fix.

Regards
Shashank
On 4/21/2016 9:25 AM, Sharma, Shashank wrote:
> On 4/20/2016 8:18 PM, Ville Syrjälä wrote:
>> On Wed, Apr 20, 2016 at 05:42:51PM +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 regression added by patch:
>>>     'commit 237ed86c693d ("drm/i915: Check live status before reading
>>> edid")'
>>>
>>> ===
>>> V2
>>> ===
>>> Ville:
>>> - Add live_status =  true in the end of delay loop.
>>>
>>> Jani:
>>> - Initialize bool live_status with false;
>>> - Change regression reference in the commit message.
>>> - Use dev_priv instead of dev
>>> - Move declaration of try at the loop
>>>
>>> Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
>>> ---
>>>   drivers/gpu/drm/i915/intel_hdmi.c | 31 ++++++++++++++++++++++++-------
>>>   1 file changed, 24 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c
>>> b/drivers/gpu/drm/i915/intel_hdmi.c
>>> index b199ede..98f5ae0 100644
>>> --- a/drivers/gpu/drm/i915/intel_hdmi.c
>>> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
>>> @@ -1398,22 +1398,39 @@ 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 try;
>>>
>>>       DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
>>>                 connector->base.id, connector->name);
>>>
>>>       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_priv)->gen >= 7 && !IS_IVYBRIDGE(dev_priv)) {
>>> +        unsigned int try;
>>> +
>>> +        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));
>>> +        }
>>>       }
>>>
>>> -    if (!live_status)
>>> -        DRM_DEBUG_KMS("Live status not up!");
>>> +    if (!live_status) {
>>> +        /*
>>> +        * TODO: Replace this with some magic code.
>>> +        * Even after giving enough delay, live status is not up.
>>> +        * Lets read EDID and decide if HDMI is available. We
>>> +        * have to do this not to break old platforms, but ideally
>>> +        * should read EDID only when live_status reg allows us.
>>> +        */
>>> +        DRM_DEBUG_KMS("Live status down, making it up\n");
>>> +        live_status = true;
>>> +    }
>>
>> Hmm. This is still not what I suggested earlier. Was there some problem
>> with my idea?
>>
> Not at all, in fact I thought I was doing just as you told. I guess I
> still missed something, please help me to understand what was that.
> our last discussion was:
>
> Ville: Sample code:
> if (don't trust live status)
> live_status = true;
>
> Shashank: Now, my question is, do you want to remove live_status check for
> VLV and other platforms too ? or this is good enough ?
>
> Ville:
> "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"
>
> Did you mean to add a kernel command-line flag type stuff for 'don't
> trust live status' or just gen_check was enough ?
>
> Regards
> Shashank
>>>
>>>       intel_hdmi_unset_edid(connector);
>>>
>>> --
>>> 1.9.1
>>