Re: [PATCH 1/2] iio: hrtimer-trigger: Mark hrtimer to expire in hard interrupt context

Stefan Agner
2020-09-24T09:01:40Z

On 2020-09-24 08:41, Sanchayan Maity wrote:
> On 20-09-22 02:51:11, Andy Duan wrote:
>> From: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
>> > On Mon, 21 Sep 2020 14:27:28 +0200
>> > Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
>> >
>> > > On 2020-09-21 10:57:03 [+0100], Jonathan Cameron wrote:
>> > > > So looking at this the other way, are there any significant risks
>> > > > associated with this change? If not I'm tempted to queue them up
>> > > > and we have the rcX time to fix anything we've missed (just like
>> > > > every other patch!)
>> > >
>> > > I've been told that it only performs IRQ-thread wake-ups in hard-IRQ
>> > > context. This is fine then.
>> > >
>> > drivers/iio/adc/vf610-adc.c
>> >
>> > However, there looks to be a lot more wrong in there than just this.
>> > So normally for a device with a data ready signal like this we would hook up as
>> > follows.
>> >
>> > Data ready #1 -> IRQ chip (trigger) -> Read sensor #1 +
>> > iio_trigger_notify_done()
>> > -> Read sensor #2 +
>> > iio_trigger_notify_done()
>> >
>> > (note that the read etc is normally in a thread - all we do in interrupt context is
>> > usually to grab a timestamp if that makes sense for a given sensor).
>> >
>> > This driver does both of.
>> > Data ready -> Read data from itself and call iio_trigger_notify_done() IRQ chip
>> > for a different trigger -> Take a timestamp and never call
>> > iio_trigger_notify_done()
>> > or read any data for that matter.
>> >
>> > Which won't do what we want at all.
>> >
>> > Andy, if I have a go at fixing this are you able to test the result?
>> > I think the simplest is probably to introduce a trigger to tie the two halves
>> > together.
>> > We can set it as the default trigger so things should keep on working for existing
>> > users.
>> >
>> > For more general case, we should probably have two functions.
>> >
>> > iio_trigger_notify_done() which is only called from places we can sleep.
>> > iio_trigger_notify_done_no_action() which only decrements the counter (or
>> > given this is only called inside industrialio-trigger.c could just replace with
>> > atomic_dec(&trig->use_count)).
>> >
>>
>> Sanchayan, can you help to verify the fixes that Jonathan will send out ?
>>
>
> Sorry for the delay in reply. Unfortunately can't as I do not access to the
> hardware having left Toradex.
>
> CCed Stefan Agner who might be able to help.
>
> @Stefan
>
> Hello Stefan :), may be you can help here?

Hi all,

I do have access to the hardware and can run a test if required. I guess
I would just need to test if ADC sampling still work with something like
tools/iio/iio_generic_buffer.c?

--
Stefan