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Commit 801954d1210a ("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: 801954d1210a ("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>