b5a2a69081
[ Upstream commit 8492bd91aa055907c67ef04f2b56f6dadd1f44bf ]
When using a high speed clock with a low baud rate, the 4x prescaler is
automatically selected if required. In that case, sc16is7xx_set_baud()
properly configures the chip registers, but returns an incorrect baud
rate by not taking into account the prescaler value. This incorrect baud
rate is then fed to uart_update_timeout().
For example, with an input clock of 80MHz, and a selected baud rate of 50,
sc16is7xx_set_baud() will return 200 instead of 50.
Fix this by first changing the prescaler variable to hold the selected
prescaler value instead of the MCR bitfield. Then properly take into
account the selected prescaler value in the return value computation.
Also add better documentation about the divisor value computation.
Fixes: dfeae619d781 ("serial: sc16is7xx")
Cc: stable@vger.kernel.org
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20240430200431.4102923-1-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.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.