i2c: recovery: if possible send STOP with recovery pulses

I2C clients may misunderstand recovery pulses if they can't read SDA to
bail out early. In the worst case, as a write operation. To avoid that
and if we can write SDA, try to send STOP to avoid the
misinterpretation.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 31d16ada6e7d9a789240cc62f50a7fcde840bb2e..301285c54603fda6ded7653ad2446c8421cb2ee2 100644 (file)
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -198,7 +198,16 @@ int i2c_generic_scl_recovery(struct i2c_adapter *adap)
 
                val = !val;
                bri->set_scl(adap, val);
-               ndelay(RECOVERY_NDELAY);
+
+               /*
+                * If we can set SDA, we will always create STOP here to ensure
+                * the additional pulses will do no harm. This is achieved by
+                * letting SDA follow SCL half a cycle later.
+                */
+               ndelay(RECOVERY_NDELAY / 2);
+               if (bri->set_sda)
+                       bri->set_sda(adap, val);
+               ndelay(RECOVERY_NDELAY / 2);
        }
 
        /* check if recovery actually succeeded */