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a09c8b3f90
Add eDMA mode support for LPI2C. There are some differences between TX DMA mode and RX DMA mode. LPI2C MTDR register is Controller Transmit Data Register. When lpi2c send data, it is tx cmd register and tx data fifo. When lpi2c receive data, it is just a rx cmd register. LPI2C MRDR register is Controller Receive Data Register, received data are stored in this. MTDR[8:10] is CMD field and MTDR[0:7] is DATA filed. +-----------+-------------------------------+ | C M D | D A T A | +---+---+---+---+---+---+---+---+---+---+---+ | 10| 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | +---+---+---+---+---+---+---+---+---+---+---+ MRDR is Controller Receive Data Register. MRDR[0:7] is DATA filed. +-------------------------------+ | D A T A | +---+---+---+---+---+---+---+---+ | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | +---+---+---+---+---+---+---+---+ When the LPI2C controller needs to send data, tx cmd and 8-bit data should be written into MTDR: CMD: 000b: Transmit the value in DATA[7:0]. DATA: 8-bit data. If lpi2c controller needs to send N 8-bit data, just write N times (CMD(W) + DATA(u8)) to MTDR. When the LPI2C controller needs to receive data, rx cmd should be written into MTDR, the received data will be stored in the MRDR. MTDR(CMD): 001b: Receive (DATA[7:0] + 1) 8-bit data. MTDR(DATA): byte counter. MRDR(DATA): 8-bit data. So when lpi2c controller needs to receive N 8-bit data, 1. N <= 256: Write 1 time (CMD(R) + BYTE COUNT(N-1)) into MTDR and receive data from MRDR. 2. N > 256: Write N/256 times (CMD(R) + BYTE COUNT(255)) + 1 time (CMD(R) + BYTE COUNT(N%256)) into MTDR and receive data from MRDR. Due to these differences, when lpi2c is in DMA TX mode, only enable TX channel to send data. But when lpi2c is in DMA RX mode, TX and RX channel are both enabled, TX channel is used to send RX cmd and RX channel is used to receive data. Signed-off-by: Carlos Song <carlos.song@nxp.com> Signed-off-by: Frank Li <frank.li@nxp.com> Link: https://lore.kernel.org/r/20241125142909.1613245-1-carlos.song@nxp.com Signed-off-by: Andi Shyti <andi.shyti@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 reStructuredText 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.