[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
TOPIC Embedded Systems
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E-mail: mike.looijmans at topic.nl
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