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Date:   Wed, 28 Aug 2019 16:19:43 +0300
From:   Mika Westerberg <mika.westerberg@linux.intel.com>
To:     Brad Campbell <lists2009@fnarfbargle.com>
Cc:     linux-kernel@vger.kernel.org, michael.jamet@intel.com,
        YehezkelShB@gmail.com
Subject: Re: Thunderbolt DP oddity on v5.2.9 on iMac 12,2
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On Wed, Aug 28, 2019 at 06:43:35PM +0800, Brad Campbell wrote:
> On 28/8/19 6:23 pm, Mika Westerberg wrote:
> 
> > On Wed, Aug 28, 2019 at 05:12:00PM +0800, Brad Campbell wrote:
> > 
> > Apart from the warning in the log (which is not fatal, I'll look into
> > it) to me the second path setup looks fine.
> > 
> > Can you do one more experiment? Boot the system up without anything
> > connected and then plug both monitors. Does it work?
> > 
> 
> Aside from head ordering issues in X it works just fine.
> I've attached the dmesg. Boot with nothing plugged in, then plug in 0-1 and
> 0-3 in that order.

OK, thanks for checking. So when Linux is in complete control both DP
tunnels get created properly. I suspect there is something different
what the firmware does compared to other Macs I've been using and that
causes the driver to fail to discover all the paths. I will take a look
at this but I'm away tomorrow and friday so it goes to next week.

BTW, have you tried to chain the two monitors?