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08ce9a1b72
This device has a silicon bug that makes it report a timeout interrupt but no data in the FIFO. The datasheet states the following in the errata section 18.1.4: "If the host reads the receive FIFO at the same time as a time-out interrupt condition happens, the host might read 0xCC (time-out) in the Interrupt Indication Register (IIR), but bit 0 of the Line Status Register (LSR) is not set (means there is no data in the receive FIFO)." The errata description seems to indicate it concerns only polled mode of operation when reading bit 0 of the LSR register. However, tests have shown and NXP has confirmed that the RXLVL register also yields 0 when the bug is triggered, and hence the IRQ driven implementation in this driver is equally affected. This bug has hit us on production units and when it does, sc16is7xx_irq() would spin forever because sc16is7xx_port_irq() keeps seeing an interrupt in the IIR register that is not cleared because the driver does not call into sc16is7xx_handle_rx() unless the RXLVL register reports at least one byte in the FIFO. Fix this by always reading one byte from the FIFO when this condition is detected in order to clear the interrupt. This approach was confirmed to be correct by NXP through their support channels. Tested by: Hugo Villeneuve <hvilleneuve@dimonoff.com> Signed-off-by: Daniel Mack <daniel@zonque.org> Co-Developed-by: Maxim Popov <maxim.snafu@gmail.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20231123072818.1394539-1-daniel@zonque.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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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.