On Mon, Nov 16, 2015 at 7:12 PM, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
> Commit d701667bb331 ("i2c: xiic: Do not reset controller before every
> transfer") removed the reinitialization of the controller before the start
> of each transfer. Apparently this change is not safe to make and the commit
> results in random I2C bus failures.
Which is the platform and the ip version that you saw the issue.
Did you see the issue with read and write as well?
.
>
> An easy way to trigger the issue is to run i2cdetect.
>
> Without the patch applied:
> 0 1 2 3 4 5 6 7 8 9 a b c d e f
> 00: -- -- -- -- -- -- -- -- -- -- -- -- --
> 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 30: -- -- -- -- -- -- -- -- UU UU -- UU 3c -- -- UU
> 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 70: -- -- -- -- -- -- -- --
>
> With the patch applied every other or so invocation:
> 0 1 2 3 4 5 6 7 8 9 a b c d e f
> 00: 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
> 10: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
> 20: 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
> 30: -- -- -- -- -- -- -- -- UU UU -- UU 3c -- -- UU
> 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 70: -- -- -- -- -- -- -- --
>
I assume that you have these many peripherals.
on the bus am I right?
> So revert the commit for now.
>
> Fixes: d701667bb331 ("i2c: xiic: Do not reset controller before every transfer")
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> ---
> drivers/i2c/busses/i2c-xiic.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
> index e23a7b0..705cf69 100644
> --- a/drivers/i2c/busses/i2c-xiic.c
> +++ b/drivers/i2c/busses/i2c-xiic.c
> @@ -662,6 +662,9 @@ static void __xiic_start_xfer(struct xiic_i2c *i2c)
>
> static void xiic_start_xfer(struct xiic_i2c *i2c)
> {
> + spin_lock(&i2c->lock);
> + xiic_reinit(i2c);
> + spin_unlock(&i2c->lock);
>
> __xiic_start_xfer(i2c);
> }
> --
> 2.1.4
>
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