Re: [PATCH 2/3] pinctrl: mcp23s08: fix irq and irqchip setup order

[Marco Felsch <m.felsch@xxxxxxxxxxxxxx>]

Hi Phil,

On 18-09-27 21:05, Phil Reid wrote:
> G'day Marco,
> 
> 
> On 25/09/2018 10:56 PM, Marco Felsch wrote:
> > Since 'commit 02e389e63e35 ("pinctrl: mcp23s08: fix irq setup order")' the
> > irq request isn't the last devm_* allocation. Without a deeper look at
> > the irq and testing this isn't a good solution. Since this driver relies
> > on the devm mechanism, requesting a interrupt should be the last thing
> > to avoid memory corruptions during unbinding.
> > 
> > 'Commit 02e389e63e35 ("pinctrl: mcp23s08: fix irq setup order")' fixed the
> > order for the interrupt-controller use case only. The
> > mcp23s08_irq_setup() must be split into two to fix it for the
> > interrupt-controller use case and to register the irq at last. So the
> > irq will be freed first during unbind.
> > 
> 
> I'm no expert on the irq's, but after a bit of reading the patch makes sense to me.
> I've got one question below.

Thanks for review.

> 
> > Cc: stable@xxxxxxxxxxxxxxx
> > Cc: Dmitry Mastykin <mastichi@xxxxxxxxx>
> > Cc: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxxxx>
> > Fixes: 82039d244f87 ("pinctrl: mcp23s08: add pinconf support")
> > Fixes: 02e389e63e35 ("pinctrl: mcp23s08: fix irq setup order")
> > Signed-off-by: Marco Felsch <m.felsch@xxxxxxxxxxxxxx>
> > ---
> >   drivers/pinctrl/pinctrl-mcp23s08.c | 15 +++++++++++++--
> >   1 file changed, 13 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pinctrl/pinctrl-mcp23s08.c b/drivers/pinctrl/pinctrl-mcp23s08.c
> > index 472746931ea8..367b648be7c7 100644
> > --- a/drivers/pinctrl/pinctrl-mcp23s08.c
> > +++ b/drivers/pinctrl/pinctrl-mcp23s08.c
> > @@ -636,6 +636,14 @@ static int mcp23s08_irq_setup(struct mcp23s08 *mcp)
> >   		return err;
> >   	}
> > +	return 0;
> > +}
> > +
> > +static int mcp23s08_irqchip_setup(struct mcp23s08 *mcp)
> > +{
> > +	struct gpio_chip *chip = &mcp->chip;
> > +	int err;
> > +
> >   	err =  gpiochip_irqchip_add_nested(chip,
> >   					   &mcp23s08_irq_chip,
> >   					   0,
> > @@ -908,8 +916,8 @@ static int mcp23s08_probe_one(struct mcp23s08 *mcp, struct device *dev,
> >   			goto fail;
> >   	}
> > -	if (mcp->irq && mcp->irq_controller) {
> > -		ret = mcp23s08_irq_setup(mcp);
> > +	if (mcp->irq_controller) {
> > +		ret = mcp23s08_irqchip_setup(mcp);
> The condition check changes, which may make sense to someone more knowledgeable.,
> but gpiochip_set_nested_irqchip in mcp23s08_irqchip_setup references mcp->irq as well
> so I'm a little confused.

You're right, it make no sense to setup a irqchip without having a
upstream irq. I will fix this for a v2.

> >   		if (ret)
> >   			goto fail;
> >   	}
> > @@ -941,6 +949,9 @@ static int mcp23s08_probe_one(struct mcp23s08 *mcp, struct device *dev,
> >   		goto fail;
> >   	}
> > +	if (mcp->irq)
> > +		ret = mcp23s08_irq_setup(mcp);
> > +
> Is there any point if it's not a irq_controller?

AFAK, if it is a irqchip/irq_controller it can be used as a irq-parent for
other devices. The irq itself can be setup without irq_controller must
be set. E.g. Inform the System about a changed gpio state.

Kind regards,
Marco
 
> 
> >   fail:
> >   	if (ret < 0)
> >   		dev_dbg(dev, "can't setup chip %d, --> %d\n", addr, ret);
> > 
> 
> Otherwise LGTM.
> 
> -- 
> Regards
> Phil Reid
> 

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