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When stopping the stream, the driver needs to ensure that ongoing DMA completes and that no new DMA is started. It does so using a feature of the PPI that can be stopped on a frame boundary. The downside of this mechanism is that the DMA can't be stopped independently of the source, which prevents usage of multiple contexts for the same source (to handle CSI-2 virtual channels or data types). Rework the stream stop mechanism to stop the write DMA without disabling the PPI first. The new mechanism relies on the combination of a state machine in the driver and shadowing of the CAL_WR_DMA_CTRL_j.MODE field in the hardware. When a stop is requested, the DMA start interrupt handler will request the hardware to stop at the end of the current frame by disabling the write DMA context in the shadowed register, and flag that a stop is in progress. The next DMA end interrupt will then report that the stop is complete. This makes it possible to stop the PPI after stopping the DMA, and fold the cal_camerarx_ppi_disable() call into cal_camerarx_stop(). Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Benoit Parrot <bparrot@ti.com> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> |
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| kernel | ||
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| README | ||
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.