[alsa-devel] [PATCH v2 2/2] ASoC: tlv320aic32x4: Add rstn gpio to platform data.

Mike Looijmans mike.looijmans at topic.nl
Thu Nov 1 16:28:59 CET 2012

On 11/01/2012 03:35 PM, Mark Brown wrote:
>> is a very nice power saving feature. I just cache all the register
>> settings up until that point (which required a bit of coding because
>> of the "paging" of the I2C address space).
> Probably easiest to just convert over to regmap, it handles paging fine.
I've backported the driver to 2.6.37 so probably my regmap wasn't smart 
enough yet.

>> It was the best I could think off at the time, and it made me wonder
>> why those reset lines aren't modelled this way more often.
> This breaks down if any of the drivers actually uses the reset pin to
> reset the chip - if the reset might not actually happen but the driver
> wants it to happen then things are going to go wrong.

Good point. But in that case, the gpio cannot be "optional", the board 
file MUST supply it.

Most chips - if not all, and this one certainly has it - also have a 
software routine for resetting it.

 From a hardware perspective, when using two codecs to get a 4-channel 
input, it makes perfect sense to use the same GPIO line to reset them 
both. This will never work with two instances of a driver that wants to 
control the GPIO line directly, but it works flawlessly when that line 
is modelled as a power supply. Each instance can request the reset to be 
relaxed, and each instance gets feedback from the supply core when the 
reset line is actually being altered (which can for example be used to 
update the codec's registers from the cache, or to indicate that the 
chip is no longer online and every write must go to the cache only).

Do I understand correctly that I'm totally alone in this and that there 
is no point in uploading the code?

Met vriendelijke groet / kind regards,

Mike Looijmans

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