[PATCH v6] i2c: imx-lpi2c: add eDMA mode support for LPI2C

[Andi Shyti]

Hi Carlos,

On Mon, Nov 25, 2024 at 10:29:09PM +0800, carlos.song at nxp.com wrote:
> From: Carlos Song <carlos.song at nxp.com>
> 
> 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 at nxp.com>
> Signed-off-by: Frank Li <frank.li at nxp.com>

merged to i2c/i2c-host.

Thanks,
Andi