Re: bq24735 charger and ac-detect

[Sebastian Reichel <sre-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

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Hi,

Ok, Darbha Sriharsha's mail address no longer works, so I Cc'd
linux-tegra instead. Maybe some of the people there have the
schematics for one of the Tegra boards using the bq24735 and/or
could check if charger presence detection actually works on
those boards with current mainline kernel.

-- Sebastian

On Wed, Dec 14, 2016 at 03:25:02PM +0100, Sebastian Reichel wrote:
> Hi Peter,
> 
> On Mon, Dec 12, 2016 at 12:12:47AM +0100, Peter Rosin wrote:
> > Hi!
> > 
> > I'm wondering about the dt bindings for the bq24735 charger. Specifically
> > the ac-detect property. The bindings say:
> 
> I don't have a device with bq24735 and the driver has been added
> before I was the maintainer of the power-supply subsystem.
> 
> >  - ti,ac-detect-gpios : This GPIO is optionally used to read the AC adapter
> >    presence. This is a Host GPIO that is configured as an input and
> >    connected to the bq24735.
> > 
> > The only way I can make sense of that is if this is the pin on the bq24735
> > that is named ACOK.
> 
> Yes. I would expect the same.
> 
> > But that pin is active high, and the code has this:
> > 
> > static bool bq24735_charger_is_present(struct bq24735 *charger)
> > {
> > 	if (charger->status_gpio)
> > 		return !gpiod_get_value_cansleep(charger->status_gpio);
> > ...
> > 
> > 
> > (status_gpio is what holds the gpio_desc of ac-detect)
> > 
> > In other words, the code seems to want a signal that is effectively
> > active low (the code negates the signal and thus returns "present"
> > when the signal is zero). The existing dts users all have active high
> > in their bindings, so it's not like they say active low to work around
> > the negation in the code...
> > 
> > This just makes no sense to me and I'm wondering what I'm missing and
> > what pin is really meant to be fed to ac-detect???
> > 
> > Yes, there is a pin on the bq24735 that is named ACDET which seems like
> > a good match, but that is a signal that is entering the bq24735. And it
> > is also active high, at least the way I read it so the problem persists...
> > 
> > Cheers,
> > Peter
> 
> As far as I can see all current users are Tegra boards and the
> driver is also from Nvidia, so let's ask them directly. I guess
> the driver was ported incorrectly and the "!" should be removed.
> 
> -- Sebastian



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