[PATCH v2] ARM: pxa27x: fix ac97 controller warm reset code

[mikedunn@newsguy.com (Mike Dunn)]

On 01/05/2013 11:11 PM, Igor Grinberg wrote:
> On 01/04/13 22:34, Robert Jarzmik wrote:
>> Igor Grinberg <grinberg@compulab.co.il> writes:
>>
>>> On 01/04/13 08:50, Igor Grinberg wrote:
>>>> On 01/03/13 16:39, Mike Dunn wrote:
>>>>> fb1bf8cd13bfa7ed0364ab0d82f717fc020d35f6 
>>>>> ([ARM] pxa: introduce processor specific pxa27x_assert_ac97reset())
>>>>> which changed the mfp to a GPIO input instead of a high output.
>>>
>>> Looking at this one more time...
>>> fb1bf8cd13 ([ARM] pxa: introduce processor specific pxa27x_assert_ac97reset())
>>> also removed the call to pxa_gpio_mode() function which effectively set
>>> AF to GPIO and configured the GPIO to output high.
>>> (Later b1d9bf1d ([ARM] pxa: remove pxa_gpio_mode() and files) removed the
>>> pxa_gpio_mode() function)
>>>
>>> See below...
>>> The DRIVE_HIGH does not really configures the GPIO to output high, but
>>> only sets the MFP_LPM_DRIVE_HIGH bit which in turn is only effective in
>>> low power modes.
>>> This means, that by doing the above, you just configure the MFP for GPIO output,
>>> but do not assign it a value, so it gets driven with some undefined value.
>>> This is not safe.
>>>
>>> Can you please, check if the attached patch below does the job?
>>
>> This is not the original behaviour before commit
>> fb1bf8cd13bfa7ed0364ab0d82f717fc020d35f6.
>>
>> The original behaviour was :
>>  - on = 1 => set GPIO as output GPIO, set to 1
>>  - on = 0 => set GPIO to the alternate function ac97reset, driven by PXA2xx AC97
>>  IP.
>>
>> If you don't set the alternate function, the GCR register usage for reset is
>> useless, isn't it ? So why do you set the GPIO as "input" with on == 0 ?
> 
> Well, I've made a quick patch for Mike to test if this works and
> since it works I will submit a proper one.
> 
> To your question about setting the direction,
> I'd like us to be on a safe side and not drive the pin if AF is not GPIO.


I just finished testing a patch that only sets the level and direction if
switching from the ac97 alt fn to gpio, and it works fine.


> Although it should not meter and changing the AF to ac97reset should do the job,
> but just to be on the safe side, as I think GPDR/GPCR/GPSR settings are preserved
> even if you change the AF to something other than GPIO.


Yes, I think this is the case, but for simplicity my patch sets GPDR and GPSR
every time the function is called.

Thanks,
Mike