From: Quanyang Wang <quanyang.w...@windriver.com>
When using i2c_smbus_read_byte_data to read one byte from a
slave device, because of the commit d358def70688
("i2c: cadence: Fix the hold bit setting"), the transaction becomes:
S Addr Wr [A] Comm [A] P S Addr Rd [A] [Data] NA P
^
CR_HOLD bit as 0
This will result that the read operation fails and will read "0xff" from
the slave device. In the SMBus protocol, it stipulates that it must follow
that command with a repeated START condition as below:
S Addr Wr [A] Comm [A] Sr Addr Rd [A] [Data] NA P
So add a check if I2C_M_NOSTART is set in flags. If set, clear the
CR_HOLD bit, or else keep CR_HOLD bit to be 1 to make sure that
the read operation begins with a repeated START.
Signed-off-by: Quanyang Wang <quanyang.w...@windriver.com>
Reviewed-by: Shubhrajyoti Datta <shubh...@xilinx.com>
Signed-off-by: Bruce Ashfield <bruce.ashfi...@gmail.com>
---
drivers/i2c/busses/i2c-cadence.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index 6b011931e090..22c1590c0e7a 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -624,10 +624,12 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
* Check for the message size against FIFO depth and set the
* 'hold bus' bit if it is greater than FIFO depth.
*/
- if ((id->recv_count > CDNS_I2C_FIFO_DEPTH) || id->bus_hold_flag)
+ if ((id->recv_count > CDNS_I2C_FIFO_DEPTH) || id->bus_hold_flag) {
ctrl_reg |= CDNS_I2C_CR_HOLD;
- else
- ctrl_reg = ctrl_reg & ~CDNS_I2C_CR_HOLD;
+ } else {
+ if (id->p_msg->flags & I2C_M_NOSTART)
+ ctrl_reg = ctrl_reg & ~CDNS_I2C_CR_HOLD;
+ }
cdns_i2c_writereg(ctrl_reg, CDNS_I2C_CR_OFFSET);
--
2.17.1
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