Re: [PATCH 12/12] i2c: pxa: enable/disable i2c module across msg xfer

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On Wednesday 03 June 2015 04:26 PM, Yi Zhang wrote:
On Tue, Jun 02, 2015 at 10:29:23PM +0530, Vaibhav Hiremath wrote:


On Tuesday 02 June 2015 10:22 PM, Vaibhav Hiremath wrote:


On Thursday 28 May 2015 06:53 PM, Russell King - ARM Linux wrote:
On Thu, May 28, 2015 at 06:33:44PM +0530, Vaibhav Hiremath wrote:
From: Yi Zhang <yizhang@xxxxxxxxxxx>

Enable i2c module/unit before transmission and disable when it finishes.

why?
It's because the i2c bus may be distrubed if the slave device,
typically a touch, powers on.

"disturbed"

I'd recommend that this is a DT property - not every platform is going to
want this, and as there is rudimentary I2C slave support in this driver,
this change breaks that.


I would take it as two different comments here, and I believe you also
meant same,

1. Not breaking I2C slave support

Not sure whether enabling/disabling module in ISR would suffice here.
To be specific, in the functions i2c_pxa_slave_start() &
i2c_pxa_slave_stop()



Please ignore this option, as enable is important to generate interrupt
on slave start.

   Yes, you are right, enabling i2c controller first is must for
   generating the interrupt


Zang,

Probably you can help me,

I am trying to introduce standard DT propertied for sclk adjustment,
meant for ILCR and IWCR register.
The datasheet I have has some confusion in terms of usage of load
counters and wait counters.

Can you please help me understand on below queries -

 1. Any additional calculation (any offset or something) I need to add
    for calculating counter values from time in nsec/usec?

 2. Counters just counts the input clock (of either 26MHz or 69MHz)?

 3. Are all counters to respective modes mutual exclusive? I mean, if I
    set fast mode, any dependency on other counters? I see IWCR.COUNT
    is common for both standard and fast mode, what about high speed
    mode?

 4. IWCR.COUNT field is meant for tHD.DATA ???

Thanks,
Vaibhav
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