kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-11-08 18:57:22 +00:00
Code Issues Releases Packages Activity
No description
1,320,961 commits 117 branches 5,824 tags 6.2 GiB
  • C 96.8%
  • Assembly 0.9%
  • Rust 0.7%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Lukas Wunner 25ae311e32 PCI: Honor Max Link Speed when determining supported speeds 
commit 3202ca2215 upstream.

The Supported Link Speeds Vector in the Link Capabilities 2 Register
indicates the *supported* link speeds.  The Max Link Speed field in the
Link Capabilities Register indicates the *maximum* of those speeds.

pcie_get_supported_speeds() neglects to honor the Max Link Speed field and
will thus incorrectly deem higher speeds as supported.  Fix it.

One user-visible issue addressed here is an incorrect value in the sysfs
attribute "max_link_speed".

But the main motivation is a boot hang reported by Niklas:  Intel JHL7540
"Titan Ridge 2018" Thunderbolt controllers supports 2.5-8 GT/s speeds,
but indicate 2.5 GT/s as maximum.  Ilpo recalls seeing this on more
devices.  It can be explained by the controller's Downstream Ports
supporting 8 GT/s if an Endpoint is attached, but limiting to 2.5 GT/s
if the port interfaces to a PCIe Adapter, in accordance with USB4 v2
sec 11.2.1:

   "This section defines the functionality of an Internal PCIe Port that
    interfaces to a PCIe Adapter. [...]
    The Logical sub-block shall update the PCIe configuration registers
    with the following characteristics: [...]
    Max Link Speed field in the Link Capabilities Register set to 0001b
    (data rate of 2.5 GT/s only).
    Note: These settings do not represent actual throughput. Throughput
    is implementation specific and based on the USB4 Fabric performance."

The present commit is not sufficient on its own to fix Niklas' boot hang,
but it is a prerequisite:  A subsequent commit will fix the boot hang by
enabling bandwidth control only if more than one speed is supported.

The GENMASK() macro used herein specifies 0 as lowest bit, even though
the Supported Link Speeds Vector ends at bit 1.  This is done on purpose
to avoid a GENMASK(0, 1) macro if Max Link Speed is zero.  That macro
would be invalid as the lowest bit is greater than the highest bit.
Ilpo has witnessed a zero Max Link Speed on Root Complex Integrated
Endpoints in particular, so it does occur in practice.  (The Link
Capabilities Register is optional on RCiEPs per PCIe r6.2 sec 7.5.3.)

Fixes: d2bd39c045 ("PCI: Store all PCIe Supported Link Speeds")
Closes: https://lore.kernel.org/r/70829798889c6d779ca0f6cd3260a765780d1369.camel@kernel.org
Link: https://lore.kernel.org/r/fe03941e3e1cc42fb9bf4395e302bff53ee2198b.1734428762.git.lukas@wunner.de
Reported-by: Niklas Schnelle <niks@kernel.org>
Tested-by: Niklas Schnelle <niks@kernel.org>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-08-20 18:30:58 +02:00
arch arm64: dts: ti: k3-j722s-evm: Fix USB gpio-hog level for Type-C 2025-08-20 18:30:57 +02:00
block block: Introduce bio_needs_zone_write_plugging() 2025-08-20 18:30:51 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: jitter - fix intermediary handling 2025-08-20 18:30:42 +02:00
Documentation Documentation: ACPI: Fix parent device references 2025-08-20 18:30:15 +02:00
drivers PCI: Honor Max Link Speed when determining supported speeds 2025-08-20 18:30:58 +02:00
fs smb: client: fix netns refcount leak after net_passive changes 2025-08-20 18:30:57 +02:00
include ata: libata-sata: Add link_power_management_supported sysfs attribute 2025-08-20 18:30:57 +02:00
init io_uring: fix breakage in EXPERT menu 2025-08-15 12:13:32 +02:00
io_uring io_uring/rw: cast rw->flags assignment to rwf_t 2025-08-20 18:30:58 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel rcu: Fix racy re-initialization of irq_work causing hangs 2025-08-20 18:30:58 +02:00
lib lib/sbitmap: convert shallow_depth from one word to the whole sbitmap 2025-08-20 18:30:49 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock 2025-08-20 18:30:55 +02:00
net net: better track kernel sockets lifetime 2025-08-20 18:30:56 +02:00
rust rust: workaround rustdoc target modifiers bug 2025-08-20 18:30:57 +02:00
samples samples: mei: Fix building on musl libc 2025-08-15 12:13:38 +02:00
scripts kconfig: lxdialog: fix 'space' to (de)select options 2025-08-20 18:30:48 +02:00
security apparmor: fix x_table_lookup when stacking is not the first entry 2025-08-20 18:30:47 +02:00
sound ASoC: fsl_sai: replace regmap_write with regmap_update_bits 2025-08-20 18:30:50 +02:00
tools tools/hv: fcopy: Fix irregularities with size of ring buffer 2025-08-20 18:30:56 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.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 MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
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 MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.42 2025-08-15 12:14:14 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.