i2c-au1550: properly terminate zero-byte transfers

Zero-bytes transfers would leave the bus transaction unfinished
(no i2c stop is sent), with the following transfer actually
sending the slave address to the previously addressed device,
resulting in weird device failures (e.g. reset minute register
values in my RTC).
This patch instructs the controller to send an I2C STOP right after
the slave address in case of a zero-byte transfer.

Signed-off-by: Manuel Lauss <mano@roarinelk.homelinux.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

diff --git a/drivers/i2c/busses/i2c-au1550.c b/drivers/i2c/busses/i2c-au1550.c
index 2f684166c43de49b19a9369651a63f36b901c005..7d51a43b38d3d5f1f97ab305141079cd4eb588c6 100644 (file)
--- a/drivers/i2c/busses/i2c-au1550.c
+++ b/drivers/i2c/busses/i2c-au1550.c
@@ -105,7 +105,7 @@ wait_master_done(struct i2c_au1550_data *adap)
 }
 
 static int
-do_address(struct i2c_au1550_data *adap, unsigned int addr, int rd)
+do_address(struct i2c_au1550_data *adap, unsigned int addr, int rd, int q)
 {
        volatile psc_smb_t      *sp;
        u32                     stat;
@@ -134,6 +134,10 @@ do_address(struct i2c_au1550_data *adap, unsigned int addr, int rd)
        if (rd)
                addr |= 1;
 
+       /* zero-byte xfers stop immediately */
+       if (q)
+               addr |= PSC_SMBTXRX_STP;
+
        /* Put byte into fifo, start up master.
        */
        sp->psc_smbtxrx = addr;
@@ -142,7 +146,7 @@ do_address(struct i2c_au1550_data *adap, unsigned int addr, int rd)
        au_sync();
        if (wait_ack(adap))
                return -EIO;
-       return 0;
+       return (q) ? wait_master_done(adap) : 0;
 }
 
 static u32
@@ -262,7 +266,8 @@ au1550_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg *msgs, int num)
 
        for (i = 0; !err && i < num; i++) {
                p = &msgs[i];
-               err = do_address(adap, p->addr, p->flags & I2C_M_RD);
+               err = do_address(adap, p->addr, p->flags & I2C_M_RD,
+                                (p->len == 0));
                if (err || !p->len)
                        continue;
                if (p->flags & I2C_M_RD)