linux-kernel - Re: Apple Thunderbolt Display chaining

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Message-ID: <YvI1lQh+C0SJiG73@lahna>
Date:   Tue, 9 Aug 2022 13:23:17 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Brad Campbell <lists2009@...rfbargle.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: Apple Thunderbolt Display chaining

Hi,

On Mon, Aug 08, 2022 at 09:27:24PM +0800, Brad Campbell wrote:
> If I don't authorize the PCIe tunnels and just leave the DP enabled it
> works fine also.

But you say that it fails on boot when the driver discovers the tunnels,
right? So there is really nothing to authorize (they should be already
"authorized" by the boot firmware).

If I understand correctly this is how it reproduces (the simplest):

  1. Connect a single Apple TB1 display to the system
  2. Boot it up
  3. Wait a while and it hangs

If this is the case, then the driver certainly is not creating any
PCIe tunnels itself unless there is a bug somewhere.

An additional question, does it reproduce with either TB1 display
connected or just with specific TB1 display?