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Manivannan Sadhasivam b27d26d07b PCI: rockchip: Use GPIOD_OUT_LOW flag while requesting ep_gpio 
commit 840b7a5edf upstream.

Rockchip platforms use 'GPIO_ACTIVE_HIGH' flag in the devicetree definition
for ep_gpio. This means, whatever the logical value set by the driver for
the ep_gpio, physical line will output the same logic level.

For instance,

  gpiod_set_value_cansleep(rockchip->ep_gpio, 0); --> Level low
  gpiod_set_value_cansleep(rockchip->ep_gpio, 1); --> Level high

But while requesting the ep_gpio, GPIOD_OUT_HIGH flag is currently used.
Now, this also causes the physical line to output 'high' creating trouble
for endpoint devices during host reboot.

When host reboot happens, the ep_gpio will initially output 'low' due to
the GPIO getting reset to its POR value. Then during host controller probe,
it will output 'high' due to GPIOD_OUT_HIGH flag. Then during
rockchip_pcie_host_init_port(), it will first output 'low' and then 'high'
indicating the completion of controller initialization.

On the endpoint side, each output 'low' of ep_gpio is accounted for PERST#
assert and 'high' for PERST# deassert. With the above mentioned flow during
host reboot, endpoint will witness below state changes for PERST#:

  (1) PERST# assert - GPIO POR state
  (2) PERST# deassert - GPIOD_OUT_HIGH while requesting GPIO
  (3) PERST# assert - rockchip_pcie_host_init_port()
  (4) PERST# deassert - rockchip_pcie_host_init_port()

Now the time interval between (2) and (3) is very short as both happen
during the driver probe(), and this results in a race in the endpoint.
Because, before completing the PERST# deassertion in (2), endpoint got
another PERST# assert in (3).

A proper way to fix this issue is to change the GPIOD_OUT_HIGH flag in (2)
to GPIOD_OUT_LOW. Because the usual convention is to request the GPIO with
a state corresponding to its 'initial/default' value and let the driver
change the state of the GPIO when required.

As per that, the ep_gpio should be requested with GPIOD_OUT_LOW as it
corresponds to the POR value of '0' (PERST# assert in the endpoint). Then
the driver can change the state of the ep_gpio later in
rockchip_pcie_host_init_port() as per the initialization sequence.

This fixes the firmware crash issue in Qcom based modems connected to
Rockpro64 based board.

Fixes: e77f847df5 ("PCI: rockchip: Add Rockchip PCIe controller support")
Closes: https://lore.kernel.org/mhi/20240402045647.GG2933@thinkpad/
Link: https://lore.kernel.org/linux-pci/20240416-pci-rockchip-perst-fix-v1-1-4800b1d4d954@linaro.org
Reported-by: Slark Xiao <slark_xiao@163.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Niklas Cassel <cassel@kernel.org>
Cc: stable@vger.kernel.org	# v4.9
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-08-03 09:00:44 +02:00
arch parisc: Fix warning at drivers/pci/msi/msi.h:121 2024-08-03 09:00:43 +02:00
block block: check bio alignment in blk_mq_submit_bio 2024-08-03 09:00:37 +02:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto This push fixes a bug in the new ecc P521 code as well as a buggy 2024-05-20 08:47:54 -07:00
Documentation KVM: PPC: Book3S HV nestedv2: Add DPDES support in helper library for Guest state buffer 2024-08-03 09:00:41 +02:00
drivers PCI: rockchip: Use GPIOD_OUT_LOW flag while requesting ep_gpio 2024-08-03 09:00:44 +02:00
fs jbd2: avoid infinite transaction commit loop 2024-08-03 09:00:40 +02:00
include fbdev: vesafb: Detect VGA compatibility from screen info's VESA attributes 2024-08-03 09:00:43 +02:00
init gcc: disable '-Warray-bounds' for gcc-9 2024-06-15 10:43:04 -07:00
io_uring io_uring: don't allow netpolling with SETUP_IOPOLL 2024-08-03 09:00:37 +02:00
ipc Mainly singleton patches, documented in their respective changelogs. 2024-05-19 14:02:03 -07:00
kernel trace/pid_list: Change gfp flags in pid_list_fill_irq() 2024-08-03 09:00:37 +02:00
lib sbitmap: fix io hung due to race on sbitmap_word::cleared 2024-08-03 09:00:26 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/mglru: fix ineffective protection calculation 2024-08-03 09:00:29 +02:00
net wifi: mac80211: chanctx emulation set CHANGE_CHANNEL when in_reconfig 2024-08-03 09:00:32 +02:00
rust rust: avoid unused import warning in rusttest 2024-06-11 23:33:28 +02:00
samples tracing/treewide: Remove second parameter of __assign_str() 2024-05-22 20:14:47 -04:00
scripts x86/syscall: Mark exit[_group] syscall handlers __noreturn 2024-08-03 08:59:12 +02:00
security task_work: s/task_work_cancel()/task_work_cancel_func()/ 2024-08-03 09:00:36 +02:00
sound ALSA: usb-audio: Add a quirk for Sonix HD USB Camera 2024-08-03 09:00:43 +02:00
tools tools/memory-model: Fix bug in lock.cat 2024-08-03 09:00:43 +02:00
usr kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
virt KVM fixes for 6.10 2024-06-21 08:03:55 -04:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.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 kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap MAINTAINERS: mailmap: update Lorenzo Stoakes's email address 2024-07-06 11:39:51 -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 pci-v6.10-fixes-2 2024-07-05 12:33:00 -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 Fixes for the I2C testunit, the Renesas R-Car driver and some 2024-07-13 16:34:22 -07:00
Makefile Linux 6.10.2 2024-07-27 11:40:36 +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.