mirror of
https://github.com/torvalds/linux.git
synced 2026-01-25 15:03:52 +08:00
affe93dd5b
It turns out having a Rx DMA channel serviced with higher priority than a Tx DMA channel is not enough to provide a well balanced DMA-based SPI transfer interface. There might still be moments when the Tx DMA channel is occasionally handled faster than the Rx DMA channel. That in its turn will eventually cause the SPI Rx FIFO overflow if SPI bus speed is high enough to fill the SPI Rx FIFO in before it's cleared by the Rx DMA channel. That's why having the DMA-based SPI Tx interface too optimized is the errors prone, so the commit0b2b66514f("spi: dw: Use DMA max burst to set the request thresholds") though being perfectly normal from the standard functionality point of view implicitly introduced the problem described above. In order to fix that the Tx DMA activity is intentionally slowed down by limiting the SPI Tx FIFO depth with a value twice bigger than the Tx burst length calculated earlier by the dw_spi_dma_maxburst_init() method. Fixes:0b2b66514f("spi: dw: Use DMA max burst to set the request thresholds") Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Cc: Andy Shevchenko <andy.shevchenko@gmail.com> Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru> Cc: Feng Tang <feng.tang@intel.com> Link: https://lore.kernel.org/r/20200721203951.2159-1-Sergey.Semin@baikalelectronics.ru Signed-off-by: Mark Brown <broonie@kernel.org>
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.