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Claudiu Beznea 977b7cc778 serial: sh-sci: Increment the runtime usage counter for the earlycon device 
commit 651dee0369 upstream.

In the sh-sci driver, serial ports are mapped to the sci_ports[] array,
with earlycon mapped at index zero.

The uart_add_one_port() function eventually calls __device_attach(),
which, in turn, calls pm_request_idle(). The identified code path is as
follows:

uart_add_one_port() ->
  serial_ctrl_register_port() ->
    serial_core_register_port() ->
      serial_core_port_device_add() ->
        serial_base_port_add() ->
          device_add() ->
            bus_probe_device() ->
              device_initial_probe() ->
                __device_attach() ->
                  // ...
                  if (dev->p->dead) {
                    // ...
                  } else if (dev->driver) {
                    // ...
                  } else {
                    // ...
                    pm_request_idle(dev);
                    // ...
                  }

The earlycon device clocks are enabled by the bootloader. However, the
pm_request_idle() call in __device_attach() disables the SCI port clocks
while earlycon is still active.

The earlycon write function, serial_console_write(), calls
sci_poll_put_char() via serial_console_putchar(). If the SCI port clocks
are disabled, writing to earlycon may sometimes cause the SR.TDFE bit to
remain unset indefinitely, causing the while loop in sci_poll_put_char()
to never exit. On single-core SoCs, this can result in the system being
blocked during boot when this issue occurs.

To resolve this, increment the runtime PM usage counter for the earlycon
SCI device before registering the UART port.

Fixes: 0b0cced19a ("serial: sh-sci: Add CONFIG_SERIAL_EARLYCON support")
Cc: stable@vger.kernel.org
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Link: https://lore.kernel.org/r/20250116182249.3828577-6-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-06-27 11:11:45 +01:00
arch x86/tools: Drop duplicate unlikely() definition in insn_decoder_test.c 2025-06-27 11:11:41 +01:00
block block: Clear BIO_EMULATES_ZONE_APPEND flag on BIO completion 2025-06-27 11:11:19 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: api - Redo lookup on EEXIST 2025-06-19 15:31:30 +02:00
Documentation dt-bindings: i2c: nvidia,tegra20-i2c: Specify the required properties 2025-06-27 11:11:44 +01:00
drivers serial: sh-sci: Increment the runtime usage counter for the earlycon device 2025-06-27 11:11:45 +01:00
fs smb: Log an error when close_all_cached_dirs fails 2025-06-27 11:11:45 +01:00
include ipv6: replace ipcm6_init calls with ipcm6_init_sk 2025-06-27 11:11:41 +01:00
init rust: clean Rust 1.88.0's unnecessary_transmutes lint 2025-05-18 08:24:51 +02:00
io_uring io_uring/sqpoll: don't put task_struct on tctx setup failure 2025-06-27 11:11:42 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel workqueue: Initialize wq_isolated_cpumask in workqueue_init_early() 2025-06-27 11:11:42 +01:00
lib pldmfw: Select CRC32 when PLDMFW is selected 2025-06-27 11:11:42 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/hugetlb: unshare page tables during VMA split, not before 2025-06-27 11:11:40 +01:00
net net: atm: fix /proc/net/atm/lec handling 2025-06-27 11:11:44 +01:00
rust rust: compile libcore with edition 2024 for 1.87+ 2025-06-27 11:11:40 +01:00
samples samples/bpf: Fix compilation failure for samples/bpf on LoongArch Fedora 2025-05-29 11:02:01 +02:00
scripts rust: compile libcore with edition 2024 for 1.87+ 2025-06-27 11:11:40 +01:00
security selinux: fix selinux_xfrm_alloc_user() to set correct ctx_len 2025-06-27 11:11:38 +01:00
sound ALSA: hda/realtek: Add quirk for Asus GU605C 2025-06-27 11:11:40 +01:00
tools bpf: Fix L4 csum update on IPv6 in CHECKSUM_COMPLETE 2025-06-27 11:11:40 +01:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Add member to struct kvm_gfn_range to indicate private/shared 2025-05-22 14:29:36 +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: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-18 08:24:51 +02:00
.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 6.12.34 2025-06-19 15:32:38 +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.