Re: [PATCH 1/2] iio: imu: st_lsm6dsx: support open drain mode

[Linus Walleij <linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

On Sun, Jun 25, 2017 at 11:34 AM, Lorenzo Bianconi
<lorenzo.bianconi83-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

>> In common with the mpu3050 which was the first driver in IIO to do open drain,

I think I implemented it on the ST sensors first actually.

>> I think you need to think about precedence as we allow for IRQF_RISING
>> and IRQF_FALLING already.  Open drain only allows for shared interrupts
>> if IRQF_FALLING (I think)
>>>       err = devm_request_threaded_irq(hw->dev, hw->irq,
>>>                                       st_lsm6dsx_handler_irq,
>>>                                       st_lsm6dsx_handler_thread,
>
> I have not got the difference between IRQF_RISING and IRQF_FALLING
> when the irq line
> is marked as shared (when open drain is enabled).
> Looking at the code, mpu3050 gyro sensor does not support shared interrupts
> with IRQF_RISING and IRQF_TRIGGER_HIGH. Is it a hw limitation?

It seems like I have inverted the logic in the MPU3050 driver.
I'll send a patch.

> Speaking with digital designer, lsm6dsx series allows open drain mode
> even if the requested irq line
> is IRQF_TRIGGER_HIGH or IRQF_RISING, we need to add a pull-down resistor.
> Moreover ST framework already supports open drain if the requested
> interrupt is IRQF_RISING.

This seems correct.

Yours,
Linus Walleij