i2c: imx-lpi2c: add eDMA mode support for LPI2C

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>

0 files changed, 0 insertions, 0 deletions