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i2c: img-scb: support I2C_M_IGNORE_NAK

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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: Sifan Naeem <sifan.naeem@imgtec.com>
Acked-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: James Hartley <james.hartley@imgtec.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Sifan Naeem 2015-11-19 09:35:13 +00:00 committed by Wolfram Sang
parent 54177ccfbe
commit c55ebe0e72
1 changed files with 10 additions and 5 deletions
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15
drivers/i2c/busses/i2c-img-scb.c
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@ -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) {
@ -1017,20 +1019,23 @@ 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.
*/
atomic = true;
if (!msgs[i].len ||
(msgs[i].flags & I2C_M_IGNORE_NAK))
atomic = true;
}
ret = clk_prepare_enable(i2c->scb_clk);