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Vidya Sagar ebfde1584d
Revert "PCI: tegra194: Enable support for 256 Byte payload"
After commit 4fb8e46c1b ("PCI: tegra194: Enable support for 256 Byte
payload"), we initialize MPS=256 for tegra194 Root Ports before enumerating
the hierarchy.

Consider an Endpoint that supports only MPS=128.  In the default situation
(CONFIG_PCIE_BUS_DEFAULT set and no "pci=pcie_bus_*" parameter), Linux
tries to configure the MPS of every device to match the upstream bridge.
If the Endpoint is directly below the Root Port, Linux can reduce the Root
Port MPS to 128 to match the Endpoint.  But if there's a switch in the
middle, Linux doesn't reduce the Root Port MPS because other devices below
the switch may already be configured with MPS larger than 128.

This scenario results in uncorrectable Malformed TLP errors if the Root
Port sends TLPs with payloads larger than 128 bytes.  These errors can
be avoided by using the "pci=pcie_bus_safe" parameter, but it doesn't
seem to be a good idea to always have this parameter even for basic
functionality to work.

Revert commit 4fb8e46c1b ("PCI: tegra194: Enable support for 256 Byte
payload") so the Root Ports default to MPS=128, which all devices
support.

If peer-to-peer DMA is not required, one can use "pci=pcie_bus_perf" to
get the benefit of larger MPS settings.

[bhelgaas: commit log; kwilczynski: retain "u16 val_16" declaration at
the top, add missing acked by tag]
Fixes: 4fb8e46c1b ("PCI: tegra194: Enable support for 256 Byte payload")
Link: https://lore.kernel.org/linux-pci/20230619102604.3735001-1-vidyas@nvidia.com
Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Cc: stable@vger.kernel.org # v6.0-rc1+
History 2023-08-03 18:33:05 +00:00
arch - Do FPU AP initialization on Xen PV too which got missed by the recent 2023-07-09 10:13:32 -07:00
block block-6.5-2023-07-03 2023-07-03 18:48:38 -07:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto This update includes the following changes: 2023-06-30 21:27:13 -07:00
Documentation Fixes for pci_clean_master, error handling in driver inits, and various 2023-07-09 09:35:51 -07:00
drivers Revert "PCI: tegra194: Enable support for 256 Byte payload" 2023-08-03 18:33:05 +00:00
fs Minor cleanups for 6.5: 2023-07-09 09:50:42 -07:00
include 16 hotfixes. Six are cc:stable and the remainder address post-6.4 issues. 2023-07-08 14:30:25 -07:00
init Kbuild updates for v6.5 2023-07-01 09:24:31 -07:00
io_uring io_uring-6.5-2023-07-03 2023-07-03 18:43:10 -07:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel dma-mapping fixes for Linux 6.5 2023-07-09 10:24:22 -07:00
lib 16 hotfixes. Six are cc:stable and the remainder address post-6.4 issues. 2023-07-08 14:30:25 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: lock newly mapped VMA with corrected ordering 2023-07-08 16:44:11 -07:00
net Including fixes from bluetooth, bpf and wireguard. 2023-07-05 15:44:45 -07:00
rust rust: error: impl Debug for Error with errname() integration 2023-06-13 01:24:42 +02:00
samples Including fixes from bluetooth, bpf and wireguard. 2023-07-05 15:44:45 -07:00
scripts A half-dozen late arriving docs patches. They are mostly fixes, but we 2023-07-06 22:15:38 -07:00
security + Bug Fixes 2023-07-07 09:55:31 -07:00
sound sound fixes for 6.5-rc1 2023-07-07 15:40:17 -07:00
tools perf tools changes and fixes for v6.5: 2nd batch 2023-07-08 10:21:51 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM64: 2023-07-03 15:32:22 -07:00
.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 Revert ".gitignore: ignore *.cover and *.mbx" 2023-07-04 15:05:12 -07:00
.mailmap 16 hotfixes. Six are cc:stable and the remainder address post-6.4 issues. 2023-07-08 14:30:25 -07:00
.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 - Address -Wmissing-prototype warnings 2023-06-26 16:43:54 -07:00
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 2: Electric Boogaloo 2023-07-09 10:29:53 -07:00
Makefile Linux 6.5-rc1 2023-07-09 13:53:13 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.