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Michal Pecio 8b2e38f2a9 usb: xhci: Avoid queuing redundant Stop Endpoint commands 
[ Upstream commit 474538b8dd ]

Stop Endpoint command on an already stopped endpoint fails and may be
misinterpreted as a known hardware bug by the completion handler. This
results in an unnecessary delay with repeated retries of the command.

Avoid queuing this command when endpoint state flags indicate that it's
stopped or halted and the command will fail. If commands are pending on
the endpoint, their completion handlers will process cancelled TDs so
it's done. In case of waiting for external operations like clearing TT
buffer, the endpoint is stopped and cancelled TDs can be processed now.

This eliminates practically all unnecessary retries because an endpoint
with pending URBs is maintained in Running state by the driver, unless
aforementioned commands or other operations are pending on it. This is
guaranteed by xhci_ring_ep_doorbell() and by the fact that it is called
every time any of those operations completes.

The only known exceptions are hardware bugs (the endpoint never starts
at all) and Stream Protocol errors not associated with any TRB, which
cause an endpoint reset not followed by restart. Sounds like a bug.

Generally, these retries are only expected to happen when the endpoint
fails to start for unknown/no reason, which is a worse problem itself,
and fixing the bug eliminates the retries too.

All cases were tested and found to work as expected. SET_DEQ_PENDING
was produced by patching uvcvideo to unlink URBs in 100us intervals,
which then runs into this case very often. EP_HALTED was produced by
restarting 'cat /dev/ttyUSB0' on a serial dongle with broken cable.
EP_CLEARING_TT by the same, with the dongle on an external hub.

Fixes: fd9d55d190 ("xhci: retry Stop Endpoint on buggy NEC controllers")
CC: stable@vger.kernel.org
Signed-off-by: Michal Pecio <michal.pecio@gmail.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20241106101459.775897-34-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-01-09 13:31:53 +01:00
arch x86/fred: Clear WFE in missing-ENDBRANCH #CPs 2025-01-09 13:31:52 +01:00
block block: avoid to reuse hctx not removed from cpuhp callback list 2025-01-02 10:32:11 +01:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: ecc - Prevent ecc_digits_from_bytes from reading too many bytes 2025-01-09 13:31:52 +01:00
Documentation ACPI/IORT: Add PMCG platform information for HiSilicon HIP09A 2025-01-09 13:31:51 +01:00
drivers usb: xhci: Avoid queuing redundant Stop Endpoint commands 2025-01-09 13:31:53 +01:00
fs btrfs: fix use-after-free when COWing tree bock and tracing is enabled 2025-01-09 13:31:52 +01:00
include cleanup: Remove address space of returned pointer 2025-01-09 13:31:53 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-09 10:32:46 +01:00
io_uring io_uring/sqpoll: fix sqpoll error handling races 2025-01-02 10:32:10 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-09 10:32:54 +01:00
kernel softirq: Allow raising SCHED_SOFTIRQ from SMP-call-function on RT kernel 2025-01-09 13:31:48 +01:00
lib lib: stackinit: hide never-taken branch from compiler 2024-12-14 19:59:57 +01:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm memblock: allow zero threshold in validate_numa_converage() 2025-01-09 13:31:40 +01:00
net Bluetooth: hci_conn: Reduce hci_conn_drop() calls in two functions 2025-01-09 13:31:43 +01:00
rust rust: macros: fix documentation of the paste! macro 2024-12-09 10:32:25 +01:00
samples samples/bpf: Fix a resource leak 2024-12-14 20:00:03 +01:00
scripts setlocalversion: work around "git describe" performance 2024-12-14 20:00:17 +01:00
security apparmor: test: Fix memory leak for aa_unpack_strdup() 2024-12-09 10:32:45 +01:00
sound ALSA: ump: Update legacy substream names upon FB info update 2025-01-09 13:31:51 +01:00
tools stddef: make __struct_group() UAPI C++-friendly 2025-01-02 10:32:03 +01:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock 2024-10-04 16:29:47 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-04 16:29:44 +02:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS membarrier: riscv: Add full memory barrier in switch_mm() 2024-09-12 11:11:45 +02:00
Makefile Linux 6.6.69 2025-01-02 10:32:11 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.