[PATCH 03/12] i2c: pxa: Add reset operation when i2c bus busy

[Robert Jarzmik]

Vaibhav Hiremath <vaibhav.hiremath at linaro.org> writes:

> From: "Jett.Zhou" <jtzhou at marvell.com>
>
> According to some test in emei_dkb, we found some i2c slave device
> (eg. camera sensor ov2659 power up) introduce noise on sda, so detect
> i2c controller busy, and assert reset to i2c controller to recover as
> early as possible to avoid more latency on the entire i2c transaction.
>
> Signed-off-by: Jett.Zhou <jtzhou at marvell.com>
> [vaibhav.hiremath at linaro.org: Removed reduction in timeout value, as I
> do not have goot explanation for it. Logically it is not required.
> And also Updated changelog]
> Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath at linaro.org>
>
> Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath at linaro.org>
> ---
>  drivers/i2c/busses/i2c-pxa.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-pxa.c b/drivers/i2c/busses/i2c-pxa.c
> index d4c798a..a76c901 100644
> --- a/drivers/i2c/busses/i2c-pxa.c
> +++ b/drivers/i2c/busses/i2c-pxa.c
> @@ -314,6 +314,10 @@ static int i2c_pxa_wait_bus_not_busy(struct pxa_i2c *i2c)
>  {
>  	int timeout = DEF_TIMEOUT;
>  
> +	if (readl(_ISR(i2c)) & (ISR_IBB | ISR_UB))
> +		i2c_pxa_reset(i2c);

The pxa27x manual states in the Developer Manual, chapter 9.4.13 "Reset
Conditions" :
            Software must ensure that (1) the I 2 C unit is not busy before it
            asserts a reset

Given that, I don't agree with this patch. Moreover, reseting unconditionaly the
i2c bus on each busy state on a write transaction for one single corner case is
not something that has my agreement. A quirk might overcome my reluctance.

Cheers.

-- 
Robert