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Mathias Nyman 2b3ffb5628 usb: hub: Don't try to recover devices lost during warm reset. 
[ Upstream commit 2521106fc7 ]

Hub driver warm-resets ports in SS.Inactive or Compliance mode to
recover a possible connected device. The port reset code correctly
detects if a connection is lost during reset, but hub driver
port_event() fails to take this into account in some cases.
port_event() ends up using stale values and assumes there is a
connected device, and will try all means to recover it, including
power-cycling the port.

Details:
This case was triggered when xHC host was suspended with DbC (Debug
Capability) enabled and connected. DbC turns one xHC port into a simple
usb debug device, allowing debugging a system with an A-to-A USB debug
cable.

xhci DbC code disables DbC when xHC is system suspended to D3, and
enables it back during resume.
We essentially end up with two hosts connected to each other during
suspend, and, for a short while during resume, until DbC is enabled back.
The suspended xHC host notices some activity on the roothub port, but
can't train the link due to being suspended, so xHC hardware sets a CAS
(Cold Attach Status) flag for this port to inform xhci host driver that
the port needs to be warm reset once xHC resumes.

CAS is xHCI specific, and not part of USB specification, so xhci driver
tells usb core that the port has a connection and link is in compliance
mode. Recovery from complinace mode is similar to CAS recovery.

xhci CAS driver support that fakes a compliance mode connection was added
in commit 8bea2bd37d ("usb: Add support for root hub port status CAS")

Once xHCI resumes and DbC is enabled back, all activity on the xHC
roothub host side port disappears. The hub driver will anyway think
port has a connection and link is in compliance mode, and hub driver
will try to recover it.

The port power-cycle during recovery seems to cause issues to the active
DbC connection.

Fix this by clearing connect_change flag if hub_port_reset() returns
-ENOTCONN, thus avoiding the whole unnecessary port recovery and
initialization attempt.

Cc: stable@vger.kernel.org
Fixes: 8bea2bd37d ("usb: Add support for root hub port status CAS")
Tested-by: Łukasz Bartosik <ukaszb@chromium.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20250623133947.3144608-1-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-08-28 16:22:53 +02:00
arch x86/mce/amd: Add default names for MCA banks and blocks 2025-08-28 16:22:53 +02:00
block block: avoid possible overflow for chunk_sectors check in blk_stack_limits() 2025-08-28 16:22:47 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:13:17 +02:00
crypto crypto: xts - Only add ecb if it is not already there 2025-06-27 11:04:01 +01:00
Documentation Documentation: ACPI: Fix parent device references 2025-08-28 16:22:39 +02:00
drivers usb: hub: Don't try to recover devices lost during warm reset. 2025-08-28 16:22:53 +02:00
fs f2fs: fix to do sanity check on ino and xnid 2025-08-28 16:22:53 +02:00
include move_mount: allow to add a mount into an existing group 2025-08-28 16:22:52 +02:00
init bpf: Clean up sockmap related Kconfigs 2025-06-27 11:04:09 +01:00
io_uring io_uring: fix possible deadlock in io_register_iowq_max_workers() 2024-11-17 14:59:39 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:04:14 +01:00
kernel ftrace: Also allocate and copy hash for reading of filter files 2025-08-28 16:22:52 +02:00
lib lib: test_objagg: Set error message in check_expect_hints_stats() 2025-07-17 18:27:47 +02:00
LICENSES
mm mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock 2025-08-28 16:22:48 +02:00
net sch_htb: make htb_deactivate() idempotent 2025-08-28 16:22:51 +02:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:22:32 +02:00
scripts kconfig: lxdialog: fix 'space' to (de)select options 2025-08-28 16:22:47 +02:00
security securityfs: don't pin dentries twice, once is enough... 2025-08-28 16:22:40 +02:00
sound ALSA: hda/realtek: Add support for HP EliteBook x360 830 G6 and EliteBook 830 G6 2025-08-28 16:22:51 +02:00
tools selftests: mptcp: connect: also cover alt modes 2025-08-28 16:22:52 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:04:11 +01:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-10-22 15:39:24 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:07:59 +02:00
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS platform: Add Surface platform directory 2025-06-27 11:04:19 +01:00
Makefile kbuild: userprogs: use correct linker when mixing clang and GNU ld 2025-08-28 16:22:52 +02:00
README

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.