b72af445cd
Some Vivante GPUs are found in systems that have interconnects restricted to 32 address bits, but may have system memory mapped above the 4GB mark. As this region isn't accessible to the GPU via DMA any GPU memory allocated in the upper part needs to go through SWIOTLB bounce buffering. This kills performance if it happens too often, as well as overrunning the available bounce buffer space, as the GPU buffer may stay mapped for a long time. Avoid bounce buffering by checking the addressing restrictions. If the GPU is unable to access memory above the 4GB mark, request our SHM buffers to be located in the DMA32 zone. Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
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.