linux-kernel - Re: [PATCH v2 2/4] iio: adc: add support for Allwinner SoCs ADC

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Date:	Thu, 21 Jul 2016 14:15:38 +0200
From:	Quentin Schulz <quentin.schulz@...e-electrons.com>
To:	Jonathan Cameron <jic23@...nel.org>, jdelvare@...e.com,
	linux@...ck-us.net, knaack.h@....de, lars@...afoo.de,
	pmeerw@...erw.net, maxime.ripard@...e-electrons.com, wens@...e.org,
	lee.jones@...aro.org
Cc:	linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
	linux-iio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	thomas.petazzoni@...e-electrons.com,
	antoine.tenart@...e-electrons.com
Subject: Re: [PATCH v2 2/4] iio: adc: add support for Allwinner SoCs ADC

On 20/07/2016 16:57, Jonathan Cameron wrote:
> On 19/07/16 09:33, Quentin Schulz wrote:
>> On 18/07/2016 15:18, Jonathan Cameron wrote:
>>> On 15/07/16 10:59, Quentin Schulz wrote:
[...]
>>>> +	enable_irq(info->temp_data_irq);
>>> Is this hardware spitting out extra irqs?  If not, much better to just
>>> leave it enabled all the time and control whether it can occur or not
>>> by controlling the device state..
>>
>> The temp_data_irq occurs every SUNXI_GPADC_TEMP_PERIOD(x) periods (in
>> the current state of the driver: 2s). What do you mean by controlling
>> the device state? Enabling or disabling the hardware part of the IP
>> responsible of getting the temperature
>> (SUNXI_GPADC_TP_TPR_TEMP_ENABLE(x) here)?
> Yes, or something along those lines if it wakes up fast enough.

The ADC wakes up fast enough but resets its internal time clock (I don't
know if it's the right term to use). Note that the temperature interrupt
occurs by period of X seconds in this IP.

This means that each time we disable the ADC on the hardware side, no
temperature interrupt will occur within the first X seconds. I don't
think this is what we want.

[...]

Quentin