diff options
author | Jann Horn <jannh@google.com> | 2020-04-01 09:46:19 +0200 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-04-16 14:46:00 +0200 |
commit | 7dbdb53d72a51cea9b921d9dbba54be00752212a (patch) | |
tree | 1a37c38cd2541ae73f9075ef1c8781e650d9225c /drivers/usb/early/xhci-dbc.h | |
parent | 056ad39ee9253873522f6469c3364964a322912b (diff) | |
download | linux-7dbdb53d72a51cea9b921d9dbba54be00752212a.tar.bz2 |
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: aeb9dd1de98c ("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>
Diffstat (limited to 'drivers/usb/early/xhci-dbc.h')
-rw-r--r-- | drivers/usb/early/xhci-dbc.h | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/drivers/usb/early/xhci-dbc.h b/drivers/usb/early/xhci-dbc.h index 673686eeddd7..6e2b7266a695 100644 --- a/drivers/usb/early/xhci-dbc.h +++ b/drivers/usb/early/xhci-dbc.h @@ -120,8 +120,22 @@ struct xdbc_ring { u32 cycle_state; }; -#define XDBC_EPID_OUT 2 -#define XDBC_EPID_IN 3 +/* + * These are the "Endpoint ID" (also known as "Context Index") values for the + * OUT Transfer Ring and the IN Transfer Ring of a Debug Capability Context data + * structure. + * According to the "eXtensible Host Controller Interface for Universal Serial + * Bus (xHCI)" specification, section "7.6.3.2 Endpoint Contexts and Transfer + * Rings", these should be 0 and 1, and those are the values AMD machines give + * you; but Intel machines seem to use the formula from section "4.5.1 Device + * Context Index", which is supposed to be used for the Device Context only. + * Luckily the values from Intel don't overlap with those from AMD, so we can + * just test for both. + */ +#define XDBC_EPID_OUT 0 +#define XDBC_EPID_IN 1 +#define XDBC_EPID_OUT_INTEL 2 +#define XDBC_EPID_IN_INTEL 3 struct xdbc_state { u16 vendor; |