[PATCH v2 2/4] iio: at91: Use different prescal, startup mask in MR for different IP

[maxime.ripard@free-electrons.com (Maxime Ripard)]

Hi Ludovic, Josh,

On Fri, Aug 23, 2013 at 05:46:03PM +0200, Desroches, Ludovic wrote:
> On Thu, Aug 22, 2013 at 05:53:00PM +0800, Josh Wu wrote:
> > On 8/22/2013 5:51 PM, Josh Wu wrote:
> > >Hi, Maxime
> > >
> > >On 8/16/2013 3:20 AM, Maxime Ripard wrote:
> > >>Hi Josh,
> > >>
> > >>On Sun, Aug 11, 2013 at 07:04:29PM +0800, Josh Wu wrote:
> > >>>For at91 boards, there are different IPs for adc. Different IPs has
> > >>>different STARTUP & PRESCAL mask in ADC_MR.
> > >>>
> > >>>This patch introduce the multiple compatible string for those
> > >>>different IPs.
> > >>>
> > >>>Signed-off-by: Josh Wu <josh.wu@atmel.com>
> > >>Overall it looks like the right ways, but I think we can take it a step
> > >>further.
> > >>
> > >>I'd drop at least the atmel,adc-drdy-mask, atmel,adc-num-channels,
> > >>atmel,adc-status-register, atmel,adc-trigger-register properties (and
> > >>probably the triggers as well description as well).
> > >
> > >yeah, right. Currently I want to drop following:
> > >
> > >atmel,adc-drdy-mask, atmel,adc-status-register,
> > >atmel,adc-trigger-register, atmel,adc-channel-base
> > >
> > >For the adc-num-channels, I'd like to leave it in dt parameters.
> > >It is a description for an adc capablity.
> 
> About this parameter, I'll remove it too from the dt bindings. To set it you
> need to have a look to the datasheet and to copy a constant value into the
> dt. From my point of view, it means than this parameter should be managed by
> the driver and by the dt.
> 
> On the other side since there are some dynamic allocation depending on this
> parameter maybe it makes sense to keep it in the dt. If the user wants to use
> only 2 channels why doing allocation for max channel number. By the way, this
> case is only valid if he uses the two first channels.

I don't recall it very well, is there any reason to not have it in the
DT? Can the ADC channels be used for something else? Or is it just some
IP-specific number of channels?

> > >
> > >For the triggers, I am not decided. An obvious benifit to remove
> > >trigger in dt will save many lines of code.
> > >
> > >>
> > >>Maxime
> > >>
> > >
> > >Best Regards,
> > >Josh Wu
> >
> 
> Since we are talking about reworking this binding I was thinking about
> resolution stuff. Filling atmel,adc-res is also copying constant value from
> the device datasheet, so if I was consistent I would say it has to be removed
> too. But I am not consistent! I mean by doing this the only thing the user
> will have to fill is the resolution value. He can't set the value he wants,
> there are only two choices. By keeping it into the dt then he will immediately
> see the choices he has.

But the resolution should probably be somehow user-defined, probably not
really related to the DT has well. I think some other IIO ADC drivers
are using sysfs files for this purpose, maybe that would be a better
fit?

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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