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Commit801954d121("serial: 8250: 8250_omap: Support native RS485") calculates RS485 delays from the baudrate. The baudrate is generated with either a 16x or 13x divisor. The divisor is set in the Mode Definition Register 1 (MDR1). The commit erroneously assumes that the register stores the divisor as a bitmask and uses a logical AND to differentiate between 16x and 13x divisors. However the divisor is really stored as a 3-bit mode (see lines 363ff in include/uapi/linux/serial_reg.h). The logical AND operation is performed with UART_OMAP_MDR1_16X_MODE, which is defined as 0x0 and hence yields false. So the commit always assumes a 13x divisor. Fix by using an equal comparison. This works because we never set any of the other 5 bits in the register. (They pertain to IrDA mode, which is not supported by the driver). Fixes:801954d121("serial: 8250: 8250_omap: Support native RS485") Link: https://lore.kernel.org/linux-serial/202211070440.8hWunFUN-lkp@intel.com/ Reported-by: kernel test robot <lkp@intel.com> Reported-by: Dan Carpenter <error27@gmail.com> Signed-off-by: Lukas Wunner <lukas@wunner.de> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Link: https://lore.kernel.org/r/7d5b04da13d89b8708b9543a0b125f2b6062a77b.1667977259.git.lukas@wunner.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.