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33bb2f6ac3
This patch reworks RX support over DMA to improve reliability: - change dma buffer cyclic configuration by using 2 periods. DMA buffer data are handled by a flip-flop between the 2 periods in order to avoid risk of data loss/corruption - change the size of dma buffer to 4096 to limit overruns - add rx errors management (breaks, parity, framing and overrun). When an error occurs on the uart line, the dma request line is masked at HW level. The SW must 1st clear DMAR (dma request line enable), to handle the error, then re-enable DMAR to recover. So, any correct data is taken from the DMA buffer, before handling the error itself. Then errors are handled from RDR/ISR/FIFO (e.g. in PIO mode). Last, DMA reception is resumed. - add a condition on DMA request line in DMA RX routines in order to switch to PIO mode when no DMA request line is disabled, even if the DMA channel is still enabled. When the UART is wakeup source and is configured to use DMA for RX, any incoming data that wakes up the system isn't correctly received. At data reception, the irq_handler handles the WUF irq, and then the data reception over DMA. As the DMA transfer has been terminated at suspend, and will be restored by resume callback (which has no yet been called by system), the data can't be received. The wake-up data has to be handled in PIO mode while suspend callback has not been called. Signed-off-by: Valentin Caron <valentin.caron@foss.st.com> Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com> Link: https://lore.kernel.org/r/20211020150332.10214-3-erwan.leray@foss.st.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.