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Date:      Tue, 27 Oct 2020 09:02:59 +0100
From:      Hans Petter Selasky <hps@selasky.org>
To:        Mark Millard <marklmi@yahoo.com>, freebsd-arm <freebsd-arm@freebsd.org>
Subject:   Re: A RPi4 xHCI VL805 problem that needs to be avoided: "xhci: quirks: add link TRB quirk for VL805"
Message-ID:  <0b70dbc4-f118-29bc-d814-8fc0a5669382@selasky.org>
In-Reply-To: <FD9CBF82-36D5-4650-8F8C-FAE0688E6F68@yahoo.com>
References:  <FD9CBF82-36D5-4650-8F8C-FAE0688E6F68.ref@yahoo.com> <FD9CBF82-36D5-4650-8F8C-FAE0688E6F68@yahoo.com>

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On 2020-10-27 00:58, Mark Millard via freebsd-arm wrote:
> https://github.com/raspberrypi/linux/pull/3929 reports:
> 
> QUOTE
> The VL805 controller can't cope with the TR Dequeue Pointer for an endpoint
> being set to a Link TRB. The hardware-maintained endpoint context ends up
> stuck at the address of the Link TRB, leading to erroneous ring expansion
> events whenever the enqueue pointer wraps to the dequeue position.
> 
> If the search for the end of the current TD and ring cycle state lands on
> a Link TRB, move to the next segment.
> END QUOTE
> 
> Also: Dealing with the link trb also toggling the ring cycle state
> is something to watch for according to the later notes.
> 

Is this an issue under FreeBSD too? Can it be reproduced?

--HPS




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