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

On Fri, Aug 23, 2013 at 06:59:36PM +0200, Maxime Ripard wrote:

Hi Ludovic, Josh,

On Fri, Aug 23, 2013 at 05:46:03PM +0200, Desroches, Ludovic wrote:

quoted

On Thu, Aug 22, 2013 at 05:53:00PM +0800, Josh Wu wrote:

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On 8/22/2013 5:51 PM, Josh Wu wrote:

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Hi, Maxime

On 8/16/2013 3:20 AM, Maxime Ripard wrote:

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Hi Josh,

On Sun, Aug 11, 2013 at 07:04:29PM +0800, Josh Wu wrote:

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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 <redacted>

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?

It is IP-specific. I don't see what benefit we could have to keep it in the DT?
But Josh seems to have arguments to keep it.

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For the triggers, I am not decided. An obvious benifit to remove
trigger in dt will save many lines of code.

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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?

It sounds to be a good solution.


Ludovic