Re: [PATCH v4 08/10] iio: adc: Support ROHM BD79124 ADC

Matti Vaittinen
2025-03-02T13:15:50Z

On 02/03/2025 06:10, Jonathan Cameron wrote:
> On Mon, 24 Feb 2025 20:34:30 +0200
> Matti Vaittinen <mazziesaccount@gmail.com> wrote:
>
>> The ROHM BD79124 is a 12-bit, 8-channel, SAR ADC. The ADC supports
>> an automatic measurement mode, with an alarm interrupt for out-of-window
>> measurements. The window is configurable for each channel.
>>
>> The I2C protocol for manual start of the measurement and data reading is
>> somewhat peculiar. It requires the master to do clock stretching after
>> sending the I2C slave-address until the slave has captured the data.
>> Needless to say this is not well suopported by the I2C controllers.
>>
>> Thus the driver does not support the BD79124's manual measurement mode
>> but implements the measurements using automatic measurement mode relying
>> on the BD79124's ability of storing latest measurements into register.
>>
>> The driver does also support configuring the threshold events for
>> detecting the out-of-window events.
>>
>> The BD79124 keeps asserting IRQ for as long as the measured voltage is
>> out of the configured window. Thus the driver masks the received event
>> for a fixed duration (1 second) when an event is handled. This prevents
>> the user-space from choking on the events
>>
>> The ADC input pins can be also configured as general purpose outputs.
>> Those pins which don't have corresponding ADC channel node in the
>> device-tree will be controllable as GPO.
>>
>> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
> Some minor stuff inline.

...

>> +#define BD79124_INTERVAL_075 0
>
> Can we make these units in these explicit?
> #define BD79124_INTERVAL_MS_0_75
> maybe? Nice to avoid need for comments on what the units are where
> you use these.
>

Sure, thanks.

>> +#define BD79124_INTERVAL_150 1
>> +#define BD79124_INTERVAL_300 2
>> +#define BD79124_INTERVAL_600 3

...

>
>> +static void bd79124_re_enable_hi(struct bd79124_data *data, unsigned int channel)
>> +{
>> + int ret, evbit = BIT(IIO_EV_DIR_RISING);
>> +
>> + if (!(data->alarm_suppressed[channel] & evbit))
>> + return;
>> +
>> + data->alarm_suppressed[channel] &= (~evbit);
>
> No brackets around the ~evbit.
> Check for other cases of this.
> Otherwise we'll get some script written 'cleanup'.

Sigh. I had a lengthy discussion about this with Andy explaining why I
like having the parenthesis to avoid any confusion. Well, I suppose I
have no options if you're strongly opposing them.

...

>> +static void bd79124_alm_enable_worker(struct work_struct *work)
>> +{
>> + int i;
>> + struct bd79124_data *data = container_of(work, struct bd79124_data,
>> + alm_enable_work.work);
>> +
>> + guard(mutex)(&data->mutex);
>> + /*
>> + * We should not re-enable the event if user has disabled it while
>> + * rate-limiting was enabled.
>> + */
>
> Is this comment suggesting something that isn't done or referring to specific
> code? I think it wants to be in the function above where the decision is made.

I have to take another look but it seems it got misplaced during the
road. Thanks!

Agreeing with all the rest, thanks!

Yours,
-- Matti