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

Mike Looijmans mike.looijmans at topic.nl
Wed Oct 31 15:40:17 CET 2012

On 10/31/2012 11:53 AM, Javier Martin wrote:
> Add the possibility to specify a gpio through platform data
> so that a HW reset can be issued to the codec.
> Signed-off-by: Javier Martin <javier.martin at vista-silicon.com>
> ---
> Changes since v1:
>   - Use a subject line according to the ASoC subsystem.
>   - Use 'devm_gpio_request_one()'
>   - Provide correct default value to the GPIO.

Now that I see your patch - I modelled the RESET pins (and the power 
supply pins) as power supply inputs, and request them to be active when 
the bias goes into standby or higher. Keeping the chip in RESET 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).

The reason that I also made RESET a "power" rather than a GPIO is that I 
have seven codecs, using three GPIO lines (in 3/3/1 configuration) to 
reset the chips. Having the RESET pin modelled as a powersupply allowed 
the codec instance to blindly turn it on, letting the powersupply keep 
track of the number of clients.

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.

If anyone's interested, I can upload the modified source. A patch is 
difficult, because I did horrible things to the code for our specific needs.

What's your view on this?


Met vriendelijke groet / kind regards,

Mike Looijmans

TOPIC Embedded Systems
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