linux-kernel - Re: Thunderbolt DP oddity on v5.2.9 on iMac 12,2

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Message-ID: <20190913082415.GA28281@lahna.fi.intel.com>
Date:   Fri, 13 Sep 2019 11:24:15 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Brad Campbell <lists2009@...rfbargle.com>
Cc:     linux-kernel@...r.kernel.org, michael.jamet@...el.com,
        YehezkelShB@...il.com
Subject: Re: Thunderbolt DP oddity on v5.2.9 on iMac 12,2

Hi Brad,

On Tue, Sep 03, 2019 at 04:33:23PM +0300, Mika Westerberg wrote:
> On Tue, Sep 03, 2019 at 08:54:02PM +0800, Brad Campbell wrote:
> > On 3/9/19 7:55 pm, Mika Westerberg wrote:
> > > On Tue, Sep 03, 2019 at 07:11:32PM +0800, Brad Campbell wrote:
> > > 
> > > I think the problem is that for some reason, probably because this is
> > > first generation hardware with all the bugs included, you cannot read
> > > the second dword from DP adapter path config space (you can write it
> > > though).
> > > 
> > > I've updated the patch so that it reads only the first dword when it
> > > discovers paths and also when it disables them. Can you try it out and
> > > see if it makes a difference? This should also get rid of the warnings
> > > you get.
> > > 
> > 
> > It would seem so. Now I get 3 heads on a cold or warm boot and no warnings
> > in the log, so it looks like that did the job. I've attached the dmesg from
> > the last cold boot for reference.
> 
> Great, thanks for checking. I will create a proper patch and submit
> upstream hopefully later this week or early next.

Unfortunately I did not have time to create a proper patch yet. I've
been busy with other things currently. Since merge window opens next
week this would have to wait until it closes anyway. I'm trying to get
this as part of a patch series I plan to submit after v5.4-rc1 is
released.