107c6b6058
commit d02b006b29de14968ba4afa998bede0d55469e29 upstream.
This reverts commit 32262e2e429cdb31f9e957e997d53458762931b7.
The commit in question claims to determine the inverse of
serial8250_get_divisor() but failed to notice that some drivers override
the default implementation using a get_divisor() callback.
This means that the computed line-speed values can be completely wrong
and results in regular TCSETS requests failing (the incorrect values
would also be passed to any overridden set_divisor() callback).
Similarly, it also failed to honour the old (deprecated) ASYNC_SPD_FLAGS
and would break applications relying on those when re-encoding the
actual line speed.
There are also at least two quirks, UART_BUG_QUOT and an OMAP1510
workaround, which were happily ignored and that are now broken.
Finally, even if the offending commit were to be implemented correctly,
this is a new feature and not something which should be backported to
stable.
Cc: Pali Rohár <pali@kernel.org>
Fixes: 32262e2e429c ("serial: 8250: Fix reporting real baudrate value in c_ospeed field")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20211007133146.28949-1-johan@kernel.org
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.