0f8e6fe09c
[ Upstream commit 3f44f7156f59cae06e9160eafb5d8b2dfd09e639 ]
Documentation for most CMTs say that it takes two input clocks before
changes propagate to the timer. This is especially relevant when the timer
is stopped to change further settings.
Implement the delays according to the spec. To avoid unnecessary delays in
atomic mode, also check if the to-be-written value actually differs.
CMCNT is a bit special because testing showed that it requires 3 cycles to
propagate, which affects all CMTs. Also, the WRFLAG needs to be checked
before writing. This fixes "cannot clear CMCNT" messages which occur often
on R-Car Gen4 SoCs, but only very rarely on older SoCs for some reason.
Fixes: 81b3b2711072 ("clocksource: sh_cmt: Add support for multiple channels per device")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20221130210609.7718-1-wsa+renesas@sang-engineering.com
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.