Hi Carlos, On Mon, Nov 25, 2024 at 10:29:09PM +0800, carlos.song@xxxxxxx wrote: > From: Carlos Song <carlos.song@xxxxxxx> > > 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@xxxxxxx> > Signed-off-by: Frank Li <frank.li@xxxxxxx> merged to i2c/i2c-host. Thanks, Andi
