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3dc4365ba8
When the CAL driver stops streaming, it will shut everything down without waiting for the current frame to finish. This leaves the CAL DMA in a slightly undefined state, and when CAL DMA is enabled when the stream is started the next time, the old DMA transfer will continue. It is not clear if the old DMA transfer continues with the exact settings of the original transfer, or is it a mix of old and new settings, but in any case the end result is memory corruption as the destination memory address is no longer valid. I could not find any way to ensure that any old DMA transfer would be discarded, except perhaps full CAL reset. But we cannot do a full reset when one port is getting enabled, as that would reset both ports. This patch tries to make sure that the DMA transfer is finished properly when the stream is being stopped. I say "tries", as, as mentioned above, I don't see a way to force the DMA transfer to finish. I believe this fixes the corruptions for normal cases, but if for some reason the DMA of the final frame would stall a lot, resulting in timeout in the code waiting for the DMA to finish, we'll again end up with unfinished DMA transfer. However, I don't know what could cause such a timeout. Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.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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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.