Date: Mon, 26 Oct 2020 16:58:20 -0700 From: Mark Millard <marklmi@yahoo.com> To: freebsd-arm <freebsd-arm@freebsd.org> Subject: A RPi4 xHCI VL805 problem that needs to be avoided: "xhci: quirks: add link TRB quirk for VL805" Message-ID: <FD9CBF82-36D5-4650-8F8C-FAE0688E6F68@yahoo.com> References: <FD9CBF82-36D5-4650-8F8C-FAE0688E6F68.ref@yahoo.com>
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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. === Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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