Re: [PATCH 6/7] i2c/pxa2xx: reset the chip if the bus is not free

[Igor Grinberg <grinberg-UTxiZqZC01RS1MOuV/RT9w@public.gmane.org>]

 Hi,

On 11/25/10 04:49, Haojian Zhuang wrote:
> On Thu, Nov 25, 2010 at 10:30 AM, Haojian Zhuang
> <haojian.zhuang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> On Thu, Nov 25, 2010 at 5:20 AM, Sebastian Andrzej Siewior
>> <bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org> wrote:
>>> I haven't seen this (yet) during a normal transfer but starting
>>> i2cdetect seems to hang the bus. On my Sodaville board, i2cdetect runs
>>> fine on bus zero and runs into timeouts on bus one and two. The chip
>>> never recovers from this condition. The following transfers hang as
>>> well. The ISR_UB never disappears.
>>> Issuing a chip reset fixes the timeout and following transfer succeed.
>>>
>>> Signed-off-by: Sebastian Andrzej Siewior <bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
>>> Signed-off-by: Dirk Brandewie <dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>>> ---
>>>  drivers/i2c/busses/i2c-pxa.c |   35 +++++++++++++++++++----------------
>>>  1 files changed, 19 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/drivers/i2c/busses/i2c-pxa.c b/drivers/i2c/busses/i2c-pxa.c
>>> index bd4b885..1a48470 100644
>>> --- a/drivers/i2c/busses/i2c-pxa.c
>>> +++ b/drivers/i2c/busses/i2c-pxa.c
>>> @@ -257,23 +257,7 @@ static void i2c_pxa_abort(struct pxa_i2c *i2c)
>>>               _ICR(i2c));
>>>  }
>>>
>>> -static int i2c_pxa_wait_bus_not_busy(struct pxa_i2c *i2c)
>>> -{
>>> -       int timeout = DEF_TIMEOUT;
>>>
>>> -       while (timeout-- && readl(_ISR(i2c)) & (ISR_IBB | ISR_UB)) {
>>> -               if ((readl(_ISR(i2c)) & ISR_SAD) != 0)
>>> -                       timeout += 4;
>>> -
>>> -               msleep(2);
>>> -               show_state(i2c);
>>> -       }
>>> -
>>> -       if (timeout < 0)
>>> -               show_state(i2c);
>>> -
>>> -       return timeout < 0 ? I2C_RETRY : 0;
>>> -}
>>>
>>>  static int i2c_pxa_wait_master(struct pxa_i2c *i2c)
>>>  {
>>> @@ -425,6 +409,25 @@ static void i2c_pxa_reset(struct pxa_i2c *i2c)
>>>        udelay(100);
>>>  }
>>>
>>> +static int i2c_pxa_wait_bus_not_busy(struct pxa_i2c *i2c)
>>> +{
>>> +       int timeout = DEF_TIMEOUT;
>>> +
>>> +       while (timeout-- && readl(_ISR(i2c)) & (ISR_IBB | ISR_UB)) {
>>> +               if ((readl(_ISR(i2c)) & ISR_SAD) != 0)
>>> +                       timeout += 4;
>>> +
>>> +               msleep(2);
>>> +               show_state(i2c);
>>> +       }
>>> +
>>> +       if (timeout < 0) {
>>> +               show_state(i2c);
>>> +               i2c_pxa_reset(i2c);
>>> +       }
>> Even you reset I2C controller, it shouldn't help you since bus isn't
>> free. I thinkt that you should reset I2C bus before you reseting I2C
>> controller.
>>
> Excuse me that my previous comments are for PXA master mode.
>
> I think that you're focused on pxa working on slave mode. But if pxa
> is working in master mode, it seems that we needn't reset I2C
> controller since it doesn't help.

As for PXA3xx, the Developer Manual states:
"Software must ensure that the TWSI unit is not busy (ISR[UB] = 0)
before it asserts a reset. Software must also ensure that the TWSI bus is idle (ISR[IBB] = 0)
when the unit is enabled after reset."

>From my experience, in master mode resetting the controller
does not help and if the bus is busy for too much time,
there always was a h/w problem involved.

>>> +
>>> +       return timeout < 0 ? I2C_RETRY : 0;
>>> +}
>>>
>>>  #ifdef CONFIG_I2C_PXA_SLAVE
>>>  /*
>>> --
>>> 1.7.3.2
>>>
>>>
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>>>
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>

-- 
Regards,
Igor.