mirror of
https://github.com/hardkernel/linux.git
synced 2026-06-02 01:06:46 +09:00
c66234cfed
When restoring registers during runtime resume, we must not write to
I2S_TXDR which is the transmit FIFO as this queues up a sample to be
output and pushes all of the output channels down by one.
This can be demonstrated with the speaker-test utility:
for i in a b c; do speaker-test -c 2 -s 1; done
which should play a test through the left speaker three times but if the
I2S hardware starts runtime suspended the first sample will be played
through the right speaker.
Fix this by marking I2S_TXDR as volatile (which also requires marking it
as readble, even though it technically isn't). This seems to be the
most robust fix, the alternative of giving I2S_TXDR a default value is
more fragile since it does not prevent regcache writing to the register
in all circumstances.
While here, also fix the configuration of I2S_RXDR and I2S_FIFOLR; these
are not writable so they do not suffer from the same problem as I2S_TXDR
but reading from I2S_RXDR does suffer from a similar problem.
Fixes: f0447f6cbb ("ASoC: rockchip: i2s: restore register during runtime_suspend/resume cycle", 2016-09-07)
Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.