Re: [PATCH] drm/i915/vlv: DP_SINK_COUNT is not reliable for valleyview platform.

From: Dave Airlie <airlied@gmail.com>
To: "Wang, Quanxian" <quanxian.wang@intel.com>
Cc: "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH] drm/i915/vlv: DP_SINK_COUNT is not reliable for valleyview platform.
Date: Wed, 25 Jun 2014 07:27:44 +1000	[thread overview]
Message-ID: <CAPM=9tzdtgzQhZiuz1qXmUYj4onx0B4b4SnVhdREZ6MQEf+Zfw@mail.gmail.com> (raw)
In-Reply-To: <50C7F552BA2A744D84D95119645BEABD0EC4CD1F@SHSMSX101.ccr.corp.intel.com>

On 23 June 2014 20:37, Wang, Quanxian <quanxian.wang@intel.com> wrote:
>
>
>> -----Original Message-----
>> From: Jani Nikula [mailto:jani.nikula@linux.intel.com]
>> Sent: Tuesday, June 17, 2014 11:38 PM
>> To: Wang, Quanxian
>> Cc: intel-gfx@lists.freedesktop.org; Daniel Vetter
>> Subject: RE: [Intel-gfx] [PATCH] drm/i915/vlv: DP_SINK_COUNT is not reliable
>> for valleyview platform.
>>
>> On Tue, 17 Jun 2014, "Wang, Quanxian" <quanxian.wang@intel.com> wrote:
>> > File dmesg_normal_20140617.log will contain dmesg log when boot the
>> > machine and start weston. (Previous is overwrite, but it is enough for
>> graphics boot message) File dmesg_error_20140617.log contains dmesg log
>> after Weston exit when it found no connector available.
>> >
>> > I disable log for  hotplug event from valleyview_irq_handler. There are so
>> many. Maybe you can find some private debug log. Don't need to care that.
>>
>> Per DP spec we need to read the SINK_COUNT. Perhaps your problem is the
>> hotplug irqs?
> [Wang, Quanxian] Hi, Jani
> The log event is about the transaction event instead of hotplug event. It is general since they will use I2c to read byte one by one. It will generate many transaction.
>
> But the root cause is really about hotplug(intel_hpd_irq_handler). When we switch to console, there will be a hotplug event happens after a while. After that, the system will continually get the hotplug event to switch sink device on and off periodly.  With DisplayPort 1.2 spec, '' This bit is used for either monitor hotplug/unplug or for notification of a sink event.", I am not sure if it is notification of  a sink event or real hotplug event. We have no code to identify the difference between hotplug/unplug  and notification of a sink event. I check display port spec and also not found how to identify them differently.
>
There are patches on the list to distinguish between short and long
hpd irqs, they are need of review.

Dave.