Hello,
Yes, I'm aware that the event TRBs that follow a COMP_SHORT_PACKET
should be COMP_SHORT_PACKET as well. That what I meant with "faulty
event TRBs".
However I wasn't aware that these event TRBs were discarded on the basis
that they didn't have a matching TD queued. Or more precisely, that the
ep_seg would turn out NULL, and then it will turn out that !ep->skip &&
(xhci->quirks & XHCI_SPURIOUS_SUCCESS) will be true, as all recent xHCI
controllers have XHCI_SPURIOUS_SUCCESS set.
So what I suggest is to move the XHCI_TRUST_TX_LENGTH fix and warning to
a place where it won't be reached if the event TRB is ignored anyhow.
This makes the code slightly uglier, but it's a catch-all solution for
all future Renesas (and similar?) chipsets.
Plus it does XHCI_TRUST_TX_LENGTH some justice: I don't think it was
meant as a way to silence warnings, but rather to handle controllers
that submit a COMP_SUCCESS TRB with a non-zero length instead of a
COMP_SHORT_PACKET.
I shall submit a patch with my suggested shortly after this mail. It
silences the warnings on my machine (without the XHCI_TRUST_TX_LENGTH
you sent to me yesterday). Please take a look.
Thanks and regards,
Eli
On 12/11/19 16:33, Mathias Nyman wrote:
On 12.11.2019 14.03, Eli Billauer wrote:
Hello,
Thanks, this patch solves the issue, as one would expect.
However I'm under the impression that the underlying problem is only
in the Event TRBs that arrive after the Event TRB of
COMP_SHORT_PACKET type. In other words, the quirky behavior is only
when the xHC flushes the Data TRBs that are left after the short
packet has arrived, and sends faulty Event TRBs on their behalf.
Specs say that the completion code of event TRBs following a
COMP_SHORT_PACKET should
also be COMP_SHORT_PACKET for a TD, so we don't expect success
completion codes.
xhci 4.10.1.1.2
"If the Short Packet occurred while processing a Transfer TRB with
only an ISP
flag set, then two events shall be generated for the transfer; one for
the Transfer
TRB that the Short Packet occurred on, and a second for the last TRB
with the
IOC flag set. Table 6-38 defines the Completion Code and TRB Transfer
Length
for the first event. In the second event, the Completion Code shall be
set to
Short Packet, and the TRB Transfer Length should be set to the same
value that
was reported by the initial Short Packet Event."
So maybe ignore any Event TRB on behalf of a TD for which a
COMP_SHORT_PACKET has been received? I mean, what information could
it possibly contain?
We kind of do. The TD is removed from list and possibly given back
after first short packet.
If a event TRB doesn't match the next queued TD on list, and the
previous TD was short,
then the event is silently ignored.
Or well, if its completion code is success you will see the warning
message you mentioned.
-Mathias
This would also have solved the "Event TRB with no TDs queued" issue,
just in a more generalized manner.
Regards,
Eli
On 12/11/19 11:36, Mathias Nyman wrote:
On 12.11.2019 6.25, Eli Billauer wrote:
Hello,
Connecting a custom designed (on FPGA) USB 3.0 device to a Renesas
uPD720202 (1912:0015) and kernel v5.3.0, I get a lot of messages in
the kernel log, while transmitting data at a high bandwidth through
a BULK IN endpoint:
handle_tx_event: 36590 callbacks suppressed
xhci_hcd 0000:03:00.0: WARN Successful completion on short TX for
slot 1 ep 18: needs XHCI_TRUST_TX_LENGTH quirk?
(last message repeated several times)
The driver in charge, as reported by lspci, is xhci_hcd.
Probably relevant details:
* The buffer size of the USB transactions is 32 kiB and up (with
libusb). With e.g. 16 kiB buffers these log messages don't appear.
* The device produces short packets occasionally. When only
full-length packets are sent, these log messages don't appear.
* Other than these log messages, everything works fine. In
particular, there are no errors in the data exchange in either
situation.
* This problem doesn't happen when running the same test on an
Intel B150 chipset’s USB 3.0 xHCI controller (8086:a12f).
I don't really know what this warning means, but this whole thing
kind-of reminds the "WARN Event TRB for slot x ep y with no TDs
queued" issue that was solved recently. Just a wild guess.
It just means that we got an event from the xHC host saying the
transfer was
completed with completion code "Success" even if we didn't get as
many bytes as was requested.
Driver is expecting a completion code of Short Packet.
Any idea how this can be fixed?
diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
index 1e0236e90687..687182afc59b 100644
--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -228,6 +228,7 @@ static void xhci_pci_quirks(struct device *dev,
struct xhci_hcd *xhci)
}
if (pdev->vendor == PCI_VENDOR_ID_RENESAS &&
pdev->device == 0x0015) {
+ xhci->quirks |= XHCI_TRUST_TX_LENGTH;
xhci->quirks |= XHCI_RESET_ON_RESUME;
xhci->quirks |= XHCI_ZERO_64B_REGS;
}
You could give it a try and see if everything works normally.
But this quirk is now quite common.
Could make sense to get rid of it completely and just handle this
case as default driver behavior.
-Mathias
