742ed5bb68
commit 5f949f140f73696f64acb89a1f16ff9153d017e0 upstream.
The driver have a race, experienced only with PREEMPT_RT patchset:
CPU0 | CPU1
==================================================================
qcom_geni_serial_probe |
uart_add_one_port |
| serdev_drv_probe
| qca_serdev_probe
| serdev_device_open
| uart_open
| uart_startup
| qcom_geni_serial_startup
| enable_irq
| __irq_startup
| WARN_ON()
| IRQ not activated
request_threaded_irq |
irq_domain_activate_irq |
The warning:
894000.serial: ttyHS1 at MMIO 0x894000 (irq = 144, base_baud = 0) is a MSM
serial serial0: tty port ttyHS1 registered
WARNING: CPU: 7 PID: 107 at kernel/irq/chip.c:241 __irq_startup+0x78/0xd8
...
qcom_geni_serial 894000.serial: serial engine reports 0 RX bytes in!
Adding UART port triggers probe of child serial devices - serdev and
eventually Qualcomm Bluetooth hci_qca driver. This opens UART port
which enables the interrupt before it got activated in
request_threaded_irq(). The issue originates in commit f3974413cf02
("tty: serial: qcom_geni_serial: Wakeup IRQ cleanup") and discussion on
mailing list [1]. However the above commit does not explain why the
uart_add_one_port() is moved above requesting interrupt.
[1] https://lore.kernel.org/all/5d9f3dfa.1c69fb81.84c4b.30bf@mx.google.com/
Fixes: f3974413cf02 ("tty: serial: qcom_geni_serial: Wakeup IRQ cleanup")
Cc: <stable@vger.kernel.org>
Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20230505152301.2181270-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
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Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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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.