linux-kernel - Re: [PATCH] pinctrl: qcom: spmi-gpio: make the irqchip immutable

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Message-ID: <87czea1i2f.wl-maz@kernel.org>
Date:   Tue, 12 Jul 2022 16:12:08 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     Robert Marko <robimarko@...il.com>, bjorn.andersson@...aro.org,
        agross@...nel.org, linus.walleij@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pinctrl: qcom: spmi-gpio: make the irqchip immutable

On Tue, 12 Jul 2022 13:44:45 +0100,
Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> wrote:
> 
> On Tue, Jul 12, 2022 at 11:42:32AM +0100, Marc Zyngier wrote:
> > On Fri, 24 Jun 2022 20:51:12 +0100,
> > Robert Marko <robimarko@...il.com> wrote:
> > > 
> > > Commit 6c846d026d49 ("gpio: Don't fiddle with irqchips marked as
> > > immutable") added a warning to indicate if the gpiolib is altering the
> > > internals of irqchips.
> > > 
> > > Following this change the following warning is now observed for the SPMI
> > > PMIC pinctrl driver:
> > > gpio gpiochip1: (200f000.spmi:pmic@0:gpio@...0): not an immutable chip, please consider fixing it!
> > > 
> > > Fix this by making the irqchip in the SPMI PMIC pinctrl driver immutable.
> > > 
> > > Signed-off-by: Robert Marko <robimarko@...il.com>
> > > ---
> > >  drivers/pinctrl/qcom/pinctrl-spmi-gpio.c | 22 ++++++++++++----------
> > >  1 file changed, 12 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c b/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
> > > index c3255b0bece4..406ee0933d0b 100644
> > > --- a/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
> > > +++ b/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
> > > @@ -171,7 +171,6 @@ struct pmic_gpio_state {
> > >  	struct regmap	*map;
> > >  	struct pinctrl_dev *ctrl;
> > >  	struct gpio_chip chip;
> > > -	struct irq_chip irq;
> > >  	u8 usid;
> > >  	u8 pid_base;
> > >  };
> > > @@ -988,6 +987,17 @@ static void *pmic_gpio_populate_parent_fwspec(struct gpio_chip *chip,
> > >  	return fwspec;
> > >  }
> > >  
> > > +static const struct irq_chip spmi_gpio_irq_chip = {
> > > +	.name		= "spmi-gpio",
> > > +	.irq_ack	= irq_chip_ack_parent,
> > > +	.irq_mask	= irq_chip_mask_parent,
> > > +	.irq_unmask	= irq_chip_unmask_parent,
> > 
> > No, this is wrong. Please look at the documentation to see how you
> > must now directly call into the gpiolib helpers for these two
> > callbacks.
> > 
> 
> IIUC, you are referring to gpiochip_disable_irq() and
> gpiochip_enable_irq() APIs.

I am indeed.

> These APIs are supposed to let the gpiolib know about that the IRQ
> usage of these GPIOs. But for the case of hierarchial IRQ domain,
> isn't the parent is going to do that?

Why would it? The parent has no clue about what sits above it. In a
hierarchical configuration, each level is responsible for its own
level, and the GPIO layer should be responsible for its own
management.

> Please correct me if I'm wrong.

I'm afraid you are, and this patch is a fairly obvious change in
behaviour, as the callbacks you mention above are not called anymore,
while they were before.

If they are not necessary (for reasons I can't fathom), then this
should be clearly explained.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.