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

[Mike Dunn]

On 01/06/2013 06:00 AM, Robert Jarzmik wrote:
> Igor Grinberg <grinberg at compulab.co.il> writes:
> 
>> On 01/04/13 22:34, Robert Jarzmik wrote:
>>> 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.
> Mmm...
> 
>> 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.
>> 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.
> 
> I think I was not clear enough.
> 
> My point is that if you program the GPIO as input, then the PXA will not drive
> the pin anymore. If you have a resistor doing the "pullup", everything will work
> (as I assume is the case in your board). If not, the AC97 codec (wm9713 and
> co...) could have its reset line asserted (ie. #RESET line), and *this* bothers me.
> 
> So changing the AC97 #RESET line to "GPIO input" is incorrect, and I don't agree
> with the patch.


I believe the extra lines in Igor's patch just effectively set the direction but
not the alt fn setting, which shouldn't do anything after the pin was configured
for the alt fn.  But in fact, I skipped those lines in the patch I prepared.  I
was too happy about discovering the reason warm reset continued to fail to
quibble :) Thanks again Igor.

Another change I made to Igor's patch is to drive the line (effectively set GPSR
bit) before switching from the ac97_reset alt fn to gpio / AF0.  Will CC you on
the patches.  They work well; warm and cold reset.  Yay!

Mike