Hi Manuel,
On Mon, 14 Jan 2008 09:46:52 +0100, Manuel Lauss wrote:
> 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!
Nice pictures, it's really helpful to be able to visualize what's
happening on the I2C bus.
>
> ---
> 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)
This approach looks much nicer than your previous proposal. I like it.
Applied, thanks!
--
Jean Delvare
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