From 91f27958d686da713c3b0a1dc205288898e44124 Mon Sep 17 00:00:00 2001 From: Manuel Lauss Date: Sun, 27 Jan 2008 18:14:52 +0100 Subject: [PATCH] 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 Signed-off-by: Jean Delvare --- drivers/i2c/busses/i2c-au1550.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/busses/i2c-au1550.c b/drivers/i2c/busses/i2c-au1550.c index 2f684166c4..7d51a43b38 100644 --- 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) -- 2.39.5