[PATCH 1/2 v1] gpio: sifive: Set affinity callback to parent

[PATCH 1/2 v1] gpio: sifive: Set affinity callback to parent

[Linus Walleij]

This assigns the .irq_set_affinity to the parent callback.
I assume the sifive GPIO can be used in systems with
SMP.

I used the pattern making the hirerarchy tolerant for missing
parent as in Marc's earlier patches.

Cc: Yash Shah <yash.shah@sifive.com>
Cc: Wesley W. Terpstra <wesley@sifive.com>
Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog RFT->v1:
- Make the affinity setting call return -EINVAL if there
  is no parent.
- Real patch because now we believe in this
---
 drivers/gpio/gpio-sifive.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpio/gpio-sifive.c b/drivers/gpio/gpio-sifive.c
index c54dd08f2cbf..485820e4488c 100644
--- a/drivers/gpio/gpio-sifive.c
+++ b/drivers/gpio/gpio-sifive.c
@@ -128,6 +128,16 @@ static void sifive_gpio_irq_eoi(struct irq_data *d)
 	irq_chip_eoi_parent(d);
 }
 
+static int sifive_gpio_irq_set_affinity(struct irq_data *data,
+					const struct cpumask *dest,
+					bool force)
+{
+	if (data->parent_data)
+		return irq_chip_set_affinity_parent(data, dest, force);
+
+	return -EINVAL;
+}
+
 static struct irq_chip sifive_gpio_irqchip = {
 	.name		= "sifive-gpio",
 	.irq_set_type	= sifive_gpio_irq_set_type,
@@ -136,6 +146,7 @@ static struct irq_chip sifive_gpio_irqchip = {
 	.irq_enable	= sifive_gpio_irq_enable,
 	.irq_disable	= sifive_gpio_irq_disable,
 	.irq_eoi	= sifive_gpio_irq_eoi,
+	.irq_set_affinity = sifive_gpio_irq_set_affinity,
 };
 
 static int sifive_gpio_child_to_parent_hwirq(struct gpio_chip *gc,
-- 
2.26.2

[PATCH 2/2 v1] gpio: tegra186: Set affinity callback to parent

[Linus Walleij]

This assigns the .irq_set_affinity to the parent callback.
I assume the Tegra186 is an SMP system so this would be
beneficial.

I used the pattern making the hirerarchy tolerant for missing
parent as in Marc's earlier patch.

Cc: Thierry Reding <treding@nvidia.com>
Cc: Vidya Sagar <vidyas@nvidia.com>
Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog RFT->v1:
- Make the affinity setting call return -EINVAL if there
  is no parent.
- Real patch because now we believe in this
---
 drivers/gpio/gpio-tegra186.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpio/gpio-tegra186.c b/drivers/gpio/gpio-tegra186.c
index 9500074b1f1b..286e0b1f46e4 100644
--- a/drivers/gpio/gpio-tegra186.c
+++ b/drivers/gpio/gpio-tegra186.c
@@ -444,6 +444,16 @@ static int tegra186_irq_set_wake(struct irq_data *data, unsigned int on)
 	return 0;
 }
 
+static int tegra186_irq_set_affinity(struct irq_data *data,
+				     const struct cpumask *dest,
+				     bool force)
+{
+	if (data->parent_data)
+		return irq_chip_set_affinity_parent(data, dest, force);
+
+	return -EINVAL;
+}
+
 static void tegra186_gpio_irq(struct irq_desc *desc)
 {
 	struct tegra_gpio *gpio = irq_desc_get_handler_data(desc);
@@ -690,6 +700,7 @@ static int tegra186_gpio_probe(struct platform_device *pdev)
 	gpio->intc.irq_unmask = tegra186_irq_unmask;
 	gpio->intc.irq_set_type = tegra186_irq_set_type;
 	gpio->intc.irq_set_wake = tegra186_irq_set_wake;
+	gpio->intc.irq_set_affinity = tegra186_irq_set_affinity;
 
 	irq = &gpio->gpio.irq;
 	irq->chip = &gpio->intc;
-- 
2.26.2

Re: [PATCH 1/2 v1] gpio: sifive: Set affinity callback to parent

[Geert Uytterhoeven]

Hi Linus,

On Tue, Nov 17, 2020 at 10:37 PM Linus Walleij <linus.walleij@linaro.org> wrote:
> This assigns the .irq_set_affinity to the parent callback.
> I assume the sifive GPIO can be used in systems with
> SMP.
>
> I used the pattern making the hirerarchy tolerant for missing
> parent as in Marc's earlier patches.
>
> Cc: Yash Shah <yash.shah@sifive.com>
> Cc: Wesley W. Terpstra <wesley@sifive.com>
> Suggested-by: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Thanks for your patch!

> ---
> ChangeLog RFT->v1:
> - Make the affinity setting call return -EINVAL if there
>   is no parent.

Would it make sense to incorporate this check into
irq_chip_set_affinity_parent(), so drivers can just point
.irq_set_affinity to the latter, without having to provide (duplicate)
the same wrapper over and over?

> - Real patch because now we believe in this
> ---
>  drivers/gpio/gpio-sifive.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpio/gpio-sifive.c b/drivers/gpio/gpio-sifive.c
> index c54dd08f2cbf..485820e4488c 100644
> --- a/drivers/gpio/gpio-sifive.c
> +++ b/drivers/gpio/gpio-sifive.c
> @@ -128,6 +128,16 @@ static void sifive_gpio_irq_eoi(struct irq_data *d)
>         irq_chip_eoi_parent(d);
>  }
>
> +static int sifive_gpio_irq_set_affinity(struct irq_data *data,
> +                                       const struct cpumask *dest,
> +                                       bool force)
> +{
> +       if (data->parent_data)
> +               return irq_chip_set_affinity_parent(data, dest, force);
> +
> +       return -EINVAL;
> +}
> +
>  static struct irq_chip sifive_gpio_irqchip = {
>         .name           = "sifive-gpio",
>         .irq_set_type   = sifive_gpio_irq_set_type,
> @@ -136,6 +146,7 @@ static struct irq_chip sifive_gpio_irqchip = {
>         .irq_enable     = sifive_gpio_irq_enable,
>         .irq_disable    = sifive_gpio_irq_disable,
>         .irq_eoi        = sifive_gpio_irq_eoi,
> +       .irq_set_affinity = sifive_gpio_irq_set_affinity,
>  };

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH 1/2 v1] gpio: sifive: Set affinity callback to parent

[Marc Zyngier]

On Tue, 06 Apr 2021 11:20:57 +0100,
Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> 
> Hi Linus,
> 
> On Tue, Nov 17, 2020 at 10:37 PM Linus Walleij <linus.walleij@linaro.org> wrote:
> > This assigns the .irq_set_affinity to the parent callback.
> > I assume the sifive GPIO can be used in systems with
> > SMP.
> >
> > I used the pattern making the hirerarchy tolerant for missing
> > parent as in Marc's earlier patches.
> >
> > Cc: Yash Shah <yash.shah@sifive.com>
> > Cc: Wesley W. Terpstra <wesley@sifive.com>
> > Suggested-by: Marc Zyngier <maz@kernel.org>
> > Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> 
> Thanks for your patch!
> 
> > ---
> > ChangeLog RFT->v1:
> > - Make the affinity setting call return -EINVAL if there
> >   is no parent.
> 
> Would it make sense to incorporate this check into
> irq_chip_set_affinity_parent(), so drivers can just point
> .irq_set_affinity to the latter, without having to provide (duplicate)
> the same wrapper over and over?

Calling one of the irq_chip_*_parent() functions assumes that there
*is* a parent at all times, because you really need to know what
context you are in by construction. There are a couple of exceptions
to this rule (irqchip state, retriggering), but overall I'd like to
stick to it and leave the checks on the implementations that have
weird setups.

I would assume that it is possible to know at the point where you map
the interrupt whether it has a parent or not, and use a different
irqchip. Is that doable in this case?

Thanks,

	M.

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

Re: [PATCH 1/2 v1] gpio: sifive: Set affinity callback to parent

[Geert Uytterhoeven]

Hi Marc,

On Tue, Apr 6, 2021 at 12:40 PM Marc Zyngier <maz@kernel.org> wrote:
> On Tue, 06 Apr 2021 11:20:57 +0100,
> Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > On Tue, Nov 17, 2020 at 10:37 PM Linus Walleij <linus.walleij@linaro.org> wrote:
> > > This assigns the .irq_set_affinity to the parent callback.
> > > I assume the sifive GPIO can be used in systems with
> > > SMP.
> > >
> > > I used the pattern making the hirerarchy tolerant for missing
> > > parent as in Marc's earlier patches.
> > >
> > > Cc: Yash Shah <yash.shah@sifive.com>
> > > Cc: Wesley W. Terpstra <wesley@sifive.com>
> > > Suggested-by: Marc Zyngier <maz@kernel.org>
> > > Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> >
> > Thanks for your patch!
> >
> > > ---
> > > ChangeLog RFT->v1:
> > > - Make the affinity setting call return -EINVAL if there
> > >   is no parent.
> >
> > Would it make sense to incorporate this check into
> > irq_chip_set_affinity_parent(), so drivers can just point
> > .irq_set_affinity to the latter, without having to provide (duplicate)
> > the same wrapper over and over?
>
> Calling one of the irq_chip_*_parent() functions assumes that there
> *is* a parent at all times, because you really need to know what
> context you are in by construction. There are a couple of exceptions
> to this rule (irqchip state, retriggering), but overall I'd like to
> stick to it and leave the checks on the implementations that have
> weird setups.
>
> I would assume that it is possible to know at the point where you map
> the interrupt whether it has a parent or not, and use a different
> irqchip. Is that doable in this case?

I think you're missing my point (or I'm missing yours ;-)

I don't mean to set up .irq_set_affinity = irq_chip_set_affinity_parent()
by default.

Right now, several drivers do this:

    static int foo_irq_set_affinity(struct irq_data *data,
                                       const struct cpumask *dest,
                                       bool force)
    {
           if (data->parent_data)
                   return irq_chip_set_affinity_parent(data, dest, force);

           return -EINVAL;
    }

    .irq_set_affinity = foo_irq_set_affinity,

If irq_chip_set_affinity_parent() would not blindly dereference
data->parent_data, there would be no need for the
foo_irq_set_affinity() wrappers.

Or are all those drivers using such a wrapper wrong?
Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH 1/2 v1] gpio: sifive: Set affinity callback to parent

[Marc Zyngier]

Hi Geert,

On Tue, 06 Apr 2021 11:51:25 +0100,
Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> 
> Hi Marc,
> 
> On Tue, Apr 6, 2021 at 12:40 PM Marc Zyngier <maz@kernel.org> wrote:
> > On Tue, 06 Apr 2021 11:20:57 +0100,
> > Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > On Tue, Nov 17, 2020 at 10:37 PM Linus Walleij <linus.walleij@linaro.org> wrote:
> > > > This assigns the .irq_set_affinity to the parent callback.
> > > > I assume the sifive GPIO can be used in systems with
> > > > SMP.
> > > >
> > > > I used the pattern making the hirerarchy tolerant for missing
> > > > parent as in Marc's earlier patches.
> > > >
> > > > Cc: Yash Shah <yash.shah@sifive.com>
> > > > Cc: Wesley W. Terpstra <wesley@sifive.com>
> > > > Suggested-by: Marc Zyngier <maz@kernel.org>
> > > > Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> > >
> > > Thanks for your patch!
> > >
> > > > ---
> > > > ChangeLog RFT->v1:
> > > > - Make the affinity setting call return -EINVAL if there
> > > >   is no parent.
> > >
> > > Would it make sense to incorporate this check into
> > > irq_chip_set_affinity_parent(), so drivers can just point
> > > .irq_set_affinity to the latter, without having to provide (duplicate)
> > > the same wrapper over and over?
> >
> > Calling one of the irq_chip_*_parent() functions assumes that there
> > *is* a parent at all times, because you really need to know what
> > context you are in by construction. There are a couple of exceptions
> > to this rule (irqchip state, retriggering), but overall I'd like to
> > stick to it and leave the checks on the implementations that have
> > weird setups.
> >
> > I would assume that it is possible to know at the point where you map
> > the interrupt whether it has a parent or not, and use a different
> > irqchip. Is that doable in this case?
> 
> I think you're missing my point (or I'm missing yours ;-)
> 
> I don't mean to set up .irq_set_affinity = irq_chip_set_affinity_parent()
> by default.
> 
> Right now, several drivers do this:
> 
>     static int foo_irq_set_affinity(struct irq_data *data,
>                                        const struct cpumask *dest,
>                                        bool force)
>     {
>            if (data->parent_data)
>                    return irq_chip_set_affinity_parent(data, dest, force);
> 
>            return -EINVAL;
>     }
> 
>     .irq_set_affinity = foo_irq_set_affinity,
> 
> If irq_chip_set_affinity_parent() would not blindly dereference
> data->parent_data, there would be no need for the
> foo_irq_set_affinity() wrappers.

The "blind dereference" is a completely assumed design choice. That's
because when you instantiate an irqchip, you know whether there is
another chip on the IRQ path, or whether this is a root (or a mux,
which amounts to the same thing).

So in most cases, you shouldn't need to check for a parent. You know
there is one by construction, and if there isn't one, you don't call
the *_parent() anyway. So unless the HW is representative of what I
describe below, a static parent/no-parent setup is preferable.

> Or are all those drivers using such a wrapper wrong?

I only know of a few drivers that have some variability around that,
which resulted in some hacks similar to what you describe. See these
patches for example:

c351ab7bf2a5 soc/tegra: pmc: Don't create fake interrupt hierarchy levels
8681cc33f817 soc/tegra: pmc: Allow optional irq parent callbacks
986ec63d4482 gpio: tegra186: Allow optional irq parent callbacks
55567976629e genirq/irqdomain: Allow partial trimming of irq_data hierarchy

This could have been avoided by restructuring the driver, but would
also have had impacts on DT, resulting in something even more horrible.

QC's PDC also suffer from a similar hack, which I plan to address once
I get this !"£$% machine to boot...

But in general, if you need to check for a parent, that's because you
are doing something that is either a bit unexpected, or has a *very*
broad spectrum (doing something generic enough that it must cope with
all possible situations).

Thanks,

	M.

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