i2c: Retry automatically on arbitration loss

Some small changes in i2c core to retry i2c xfers until either the
maximum number of retries or the timeout is hit.

Signed-off-by: Clifford Wolf <clifford@clifford.at>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 26 insertions, 4 deletions

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index dfd7bc8094b..635c488262c 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -1022,7 +1022,8 @@ module_exit(i2c_exit);
  */
 int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 {
-        int ret;
+        unsigned long orig_jiffies;
+        int ret, try;
 
         /* REVISIT the fault reporting model here is weak:
          *
@@ -1060,7 +1061,15 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
                         mutex_lock_nested(&adap->bus_lock, adap->level);
                 }
 
-                ret = adap->algo->master_xfer(adap,msgs,num);
+                /* Retry automatically on arbitration loss */
+                orig_jiffies = jiffies;
+                for (ret = 0, try = 0; try <= adap->retries; try++) {
+                        ret = adap->algo->master_xfer(adap, msgs, num);
+                        if (ret != -EAGAIN)
+                                break;
+                        if (time_after(jiffies, orig_jiffies + adap->timeout))
+                                break;
+                }
                 mutex_unlock(&adap->bus_lock);
 
                 return ret;
@@ -1995,14 +2004,27 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
                    char read_write, u8 command, int protocol,
                    union i2c_smbus_data *data)
 {
+        unsigned long orig_jiffies;
+        int try;
         s32 res;
 
         flags &= I2C_M_TEN | I2C_CLIENT_PEC;
 
         if (adapter->algo->smbus_xfer) {
                 mutex_lock(&adapter->bus_lock);
-                res = adapter->algo->smbus_xfer(adapter,addr,flags,read_write,
-                                                command, protocol, data);
+
+                /* Retry automatically on arbitration loss */
+                orig_jiffies = jiffies;
+                for (res = 0, try = 0; try <= adapter->retries; try++) {
+                        res = adapter->algo->smbus_xfer(adapter, addr, flags,
+                                                        read_write, command,
+                                                        protocol, data);
+                        if (res != -EAGAIN)
+                                break;
+                        if (time_after(jiffies,
+                                       orig_jiffies + adapter->timeout))
+                                break;
+                }
                 mutex_unlock(&adapter->bus_lock);
         } else
                 res = i2c_smbus_xfer_emulated(adapter,addr,flags,read_write,