Hi Jean, Here is my third try to fix the corrupted RTC minute register on my board in conjunction with the i2c-au1550 driver.
Here's a trace of the controller accessing the RTC (0xA2): http://mlau.at/files/i2c-au1550-original_behav.png Notice the missing stop condition after the quick probe. Here's a trace with the patch applied: http://mlau.at/files/i2c-au1550-misbehavior-patch-behav.png Please apply! --- >From 443520b88bda030ba304dcbbbf14f977abad5ff5 Mon Sep 17 00:00:00 2001 From: Manuel Lauss <[EMAIL PROTECTED]> Date: Mon, 14 Jan 2008 09:28:11 +0100 Subject: [PATCH] i2c: 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 <[EMAIL PROTECTED]> --- drivers/i2c/busses/i2c-au1550.c | 11 ++++++++--- 1 files changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/busses/i2c-au1550.c b/drivers/i2c/busses/i2c-au1550.c index 2f68416..7d51a43 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) -- 1.5.3.7 _______________________________________________ i2c mailing list [email protected] http://lists.lm-sensors.org/mailman/listinfo/i2c
