[PATCH 3.16 049/192] i2c: cadance: fix ctrl/addr reg write order

Ben Hutchings
2017-10-09T13:48:57Z

From: Matt Weber <matthew.weber@rockwellcollins.com>

commit 8064c616984eaa015f018dba595d78cd24a0cc8c upstream.

The driver was clearing the hold bit in the control register before
writing to the address register which resulted in a stop condition
being generated rather than a repeated start.

This issue was only observed when a system was running much
slower than a normal processor would execute. The IP data sheet
mentions a ordering of writing to the address register before
clearing the hold.

Fixes: df8eb5691c4 ("i2c: Add driver for Cadence I2C controller")
Signed-off-by: John Linn <john.linn@xilinx.com>
Signed-off-by: Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>
Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/i2c/busses/i2c-cadence.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -340,14 +340,14 @@ static void cdns_i2c_mrecv(struct cdns_i
CDNS_I2C_XFER_SIZE_OFFSET);
else
cdns_i2c_writereg(id->recv_count, CDNS_I2C_XFER_SIZE_OFFSET);
+ /* Set the slave address in address register - triggers operation */
+ cdns_i2c_writereg(id->p_msg->addr & CDNS_I2C_ADDR_MASK,
+ CDNS_I2C_ADDR_OFFSET);
/* Clear the bus hold flag if bytes to receive is less than FIFO size */
if (!id->bus_hold_flag &&
((id->p_msg->flags & I2C_M_RECV_LEN) != I2C_M_RECV_LEN) &&
(id->recv_count <= CDNS_I2C_FIFO_DEPTH))
cdns_i2c_clear_bus_hold(id);
- /* Set the slave address in address register - triggers operation */
- cdns_i2c_writereg(id->p_msg->addr & CDNS_I2C_ADDR_MASK,
- CDNS_I2C_ADDR_OFFSET);
cdns_i2c_writereg(CDNS_I2C_ENABLED_INTR_MASK, CDNS_I2C_IER_OFFSET);
}