From: Clifford Wolf <clifford@xxxxxxxxxxx>
Simply retry on arbitration lost until xfer is successfull, a
non-arbitration-lost error is triggered or the 1s timeout is hit.
Tested with a freescale MPC8349E host cpu.
Signed-off-by: Clifford Wolf <clifford@xxxxxxxxxxx>
Cc: Jean Delvare <khali@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/i2c/busses/i2c-mpc.c | 22 ++++++++++++++--------
1 file changed, 14 insertions(+), 8 deletions(-)
diff -puN drivers/i2c/busses/i2c-mpc.c~i2c-fix-i2c-mpc-driver-for-multi-master-i2c-busses drivers/i2c/busses/i2c-mpc.c
--- a/drivers/i2c/busses/i2c-mpc.c~i2c-fix-i2c-mpc-driver-for-multi-master-i2c-busses
+++ a/drivers/i2c/busses/i2c-mpc.c
@@ -134,13 +134,13 @@ static int i2c_wait(struct mpc_i2c *i2c,
if (result < 0)
return result;
- if (!(x & CSR_MCF)) {
- pr_debug("I2C: unfinished\n");
- return -EIO;
- }
-
if (x & CSR_MAL) {
pr_debug("I2C: MAL\n");
+ return -EAGAIN;
+ }
+
+ if (!(x & CSR_MCF)) {
+ pr_debug("I2C: unfinished\n");
return -EIO;
}
@@ -257,11 +257,11 @@ static int mpc_read(struct mpc_i2c *i2c,
static int mpc_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
struct i2c_msg *pmsg;
- int i;
- int ret = 0;
+ int i, ret;
unsigned long orig_jiffies = jiffies;
struct mpc_i2c *i2c = i2c_get_adapdata(adap);
+restart:
mpc_i2c_start(i2c);
/* Allow bus up to 1s to become not busy */
@@ -281,7 +281,7 @@ static int mpc_xfer(struct i2c_adapter *
schedule();
}
- for (i = 0; ret >= 0 && i < num; i++) {
+ for (i = 0, ret = 0; ret >= 0 && i < num; i++) {
pmsg = &msgs[i];
pr_debug("Doing %s %d bytes to 0x%02x - %d of %d messages\n",
pmsg->flags & I2C_M_RD ? "read" : "write",
@@ -292,7 +292,13 @@ static int mpc_xfer(struct i2c_adapter *
else
ret =
mpc_write(i2c, pmsg->addr, pmsg->buf, pmsg->len, i);
+ if (ret == -EAGAIN) {
+ pr_debug("Lost i2c arbitration -> retry.\n");
+ mpc_i2c_stop(i2c);
+ goto restart;
+ }
}
+
mpc_i2c_stop(i2c);
return (ret < 0) ? ret : num;
}
_
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