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Commit c55ebe0e authored by Sifan Naeem's avatar Sifan Naeem Committed by Wolfram Sang
Browse files

i2c: img-scb: support I2C_M_IGNORE_NAK 



This commit adds support for the I2C_M_IGNORE_NAK protocol
modification.

Such behaviour can only be implemented in atomic mode. So, if a
transaction contains a message with such flag the drivers
switches to atomic mode. The implementation consists simply in
treating NAKs as ACKs.

Signed-off-by: default avatarSifan Naeem <sifan.naeem@imgtec.com>
Acked-by: default avatarJames Hogan <james.hogan@imgtec.com>
Reviewed-by: default avatarJames Hartley <james.hartley@imgtec.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 54177ccf

drivers/i2c/busses/i2c-img-scb.c

+10 −5
Original line number Diff line number Diff line
@@ -750,7 +750,9 @@ static unsigned int img_i2c_atomic(struct img_i2c *i2c, 
			next_cmd = CMD_RET_ACK;

		break;

	case CMD_RET_ACK:

		if (i2c->line_status & LINESTAT_ACK_DET) {

		if (i2c->line_status & LINESTAT_ACK_DET ||

		    (i2c->line_status & LINESTAT_NACK_DET &&

		    i2c->msg.flags & I2C_M_IGNORE_NAK)) {

			if (i2c->msg.len == 0) {

				next_cmd = CMD_GEN_STOP;

			} else if (i2c->msg.flags & I2C_M_RD) {
@@ -1017,19 +1019,22 @@ static int img_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, 
		return -EIO;



	for (i = 0; i < num; i++) {

		if (likely(msgs[i].len))

			continue;

		/*

		 * 0 byte reads are not possible because the slave could try

		 * and pull the data line low, preventing a stop bit.

		 */

		if (unlikely(msgs[i].flags & I2C_M_RD))

		if (!msgs[i].len && msgs[i].flags & I2C_M_RD)

			return -EIO;

		/*

		 * 0 byte writes are possible and used for probing, but we

		 * cannot do them in automatic mode, so use atomic mode

		 * instead.

		 *

		 * Also, the I2C_M_IGNORE_NAK mode can only be implemented

		 * in atomic mode.

		 */

		if (!msgs[i].len ||

		    (msgs[i].flags & I2C_M_IGNORE_NAK))

			atomic = true;

	}