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887e359d6c
This patch prepares the driver to use more than one RX-FIFO. Having a bigger RX buffer is beneficial in high load situations, where the system temporarily cannot keep up reading CAN frames from the chip. Using a bigger RX buffer also allows to implement RX IRQ coalescing, which will be added in a later patch series. If using more than 1 RX-FIFO the driver has to figure out, which FIFOs have RX'ed CAN frames pending. This is indicated by a set bit in the RXIF register, which is positioned directly after the interrupt status register INT. If more than 1 RX-FIFO is used, the driver reads both registers in 1 transfer. The mcp251xfd_handle_rxif() function iterates over all RX rings and reads out the RX'ed CAN frames for for all pending FIFOs. To keep the logic for the 1 RX-FIFO only case in mcp251xfd_handle_rxif() simple, the driver marks that FIFO pending in mcp251xfd_ring_init(). The chip has a dedicated RX interrupt line to signal pending RX'ed frames. If connected to an input GPIO and the driver will skip the initial read of the interrupt status register (INT) and directly read the pending RX'ed frames if the line is active. The driver assumes the 1st RX-FIFO pending (a read of the RXIF register would re-introduce the skipped initial read of the INT register). Any other pending RX-FIFO will be served in the main interrupt handler. Link: https://lore.kernel.org/all/20220217103826.2299157-8-mkl@pengutronix.de Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de> |
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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.