mirror of https://gitee.com/openkylin/linux.git
73a47bd0da
SYS/RT/Audio DMAC includes independent data buffers for reading
and writing. Therefore, the read transfer counter and write transfer
counter have different values.
TCR indicates read counter, and TCRB indicates write counter.
The relationship is like below.
TCR TCRB
[SOURCE] -> [DMAC] -> [SINK]
In the MEM_TO_DEV direction, what really matters is how much data has
been written to the device. If the DMA is interrupted between read and
write, then, the data doesn't end up in the destination, so shouldn't
be counted. TCRB is thus the register we should use in this cases.
In the DEV_TO_MEM direction, the situation is more complex. Both the
read and write side are important. What matters from a data consumer
point of view is how much data has been written to memory.
On the other hand, if the transfer is interrupted between read and
write, we'll end up losing data. It can also be important to report.
In the MEM_TO_MEM direction, what matters is of course how much data
has been written to memory from data consumer point of view.
Here, because read and write have independent data buffers, it will
take a while for TCR and TCRB to become equal. Thus we should check
TCRB in this case, too.
Thus, all cases we should check TCRB instead of TCR.
Without this patch, Sound Capture has noise after PulseAudio support
(=
|
||
|---|---|---|
| Documentation | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
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.