linux/drivers/usb/early
Jann Horn 7dbdb53d72 USB: early: Handle AMD's spec-compliant identifiers, too
This fixes a bug that causes the USB3 early console to freeze after
printing a single line on AMD machines because it can't parse the
Transfer TRB properly.

The spec at
https://www.intel.com/content/dam/www/public/us/en/documents/technical-specifications/extensible-host-controler-interface-usb-xhci.pdf
says in section "4.5.1 Device Context Index" that the Context Index,
also known as Endpoint ID according to
section "1.6 Terms and Abbreviations", is normally computed as
`DCI = (Endpoint Number * 2) + Direction`, which matches the current
definitions of XDBC_EPID_OUT and XDBC_EPID_IN.

However, the numbering in a Debug Capability Context data structure is
supposed to be different:
Section "7.6.3.2 Endpoint Contexts and Transfer Rings" explains that a
Debug Capability Context data structure has the endpoints mapped to indices
0 and 1.

Change XDBC_EPID_OUT/XDBC_EPID_IN to the spec-compliant values, add
XDBC_EPID_OUT_INTEL/XDBC_EPID_IN_INTEL with Intel's incorrect values, and
let xdbc_handle_tx_event() handle both.

I have verified that with this patch applied, the USB3 early console works
on both an Intel and an AMD machine.

Fixes: aeb9dd1de9 ("usb/early: Add driver for xhci debug capability")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20200401074619.8024-1-jannh@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-04-16 14:46:00 +02:00
..
ehci-dbgp.c drivers: usb: early: clean up indentation, remove extraneous tabs 2018-11-23 16:13:14 +01:00
Makefile USB: add SPDX identifiers to all remaining Makefiles 2017-11-07 15:53:48 +01:00
xhci-dbc.c USB: early: Handle AMD's spec-compliant identifiers, too 2020-04-16 14:46:00 +02:00
xhci-dbc.h USB: early: Handle AMD's spec-compliant identifiers, too 2020-04-16 14:46:00 +02:00