linux-kernel - Re: [PATCH v5] mfd: tqmx86: IO controller with i2c, wachdog and gpio

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Date:   Thu, 7 Feb 2019 14:37:45 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     linux-kernel@...r.kernel.org,
        Emeric Dupont <emeric.dupont@....aero>
Subject: Re: [PATCH v5] mfd: tqmx86: IO controller with i2c, wachdog and gpio

> > +			dev_warn(dev, "GPIO interrupts not supported.\n");
> 
> Do you know why they wouldn't be supported?
> 
> Isn't that the point of the device?

Hi Lee

I don't know the history of this device, but i suspect it has been
through a number of revisions. The vendor driver suggests some
versions support interrupts from the I2C bus master, but the version i
have does not. As a result the i2c bus master has to do polled
IO. GPIO interrupts are optional in the GPIO world. So it could be
some versions don't support it. But the version i have does.

It seems like if you write to bits of the interrupt configuration
register on a revision which don't support interrupts, the write does
not stick. So reading it back then lets you know this. The GPIO still
works for plain I and O, but don't expect interrupts to work.

      Andrew