Re: [PATCH v2 2/2] serial: sc16is7xx: hard reset the chip if reset-gpios is defined in dt

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On Wed, Jun 5, 2024 at 1:55 PM Hui Wang <hui.wang@xxxxxxxxxxxxx> wrote:
> On 6/5/24 18:30, Maarten Brock wrote:
> >> From: Hugo Villeneuve <hugo@xxxxxxxxxxx>
> >> Sent: Tuesday, 4 June 2024 16:23

<...>

> >> Add function description from original comment "Reset device,
> >> purging any pending irq / data", since the comment applies to both
> >> hardware and software reset,
> > No it does not (at this moment). See below.

...

> > The problem here is that this only deasserts the reset if it were asserted before.
> > Nothing happens if it already was deasserted. This makes the delay also pretty
> > useless.
> >
> > To make this a proper reset pulse for the device you must first assert the reset,
> > then wait >3us, and finally deassert the reset.

> My understanding is when calling devm_gpiod_get_optional(dev, "reset",
> GPIOD_OUT_LOW) and returning a valid (gpio_desc *), the flag
> GPIOD_OUT_LOW guarantees the GPIO is set to output and low (assert the
> reset pin).

No, this is logical, not physical state. Maarten is correct. How did
you test this?

-- 
With Best Regards,
Andy Shevchenko





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