linux-kernel - Re: [PATCH v3] thermal: rcar_thermal: Use platform_get_irq

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Date:   Thu, 6 Jan 2022 16:29:41 +0100
From:   Niklas Söderlund 
        <niklas.soderlund@...natech.se>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] thermal: rcar_thermal: Use
 platform_get_irq_optional() to get the interrupt

Hi Lad,

On 2022-01-05 19:25:25 +0000, Lad, Prabhakar wrote:
> Hi Niklas,
> 
> Thank you for the review.
> 
> On Wed, Jan 5, 2022 at 7:13 PM Niklas Söderlund
> <niklas.soderlund@...natech.se> wrote:
> >
> > Hi Lad,
> >
> > Thanks for your work.
> >
> > On 2022-01-04 14:52:11 +0000, Lad Prabhakar wrote:
> > > platform_get_resource(pdev, IORESOURCE_IRQ, ..) relies on static
> > > allocation of IRQ resources in DT core code, this causes an issue
> > > when using hierarchical interrupt domains using "interrupts" property
> > > in the node as this bypasses the hierarchical setup and messes up the
> > > irq chaining.
> > >
> > > In preparation for removal of static setup of IRQ resource from DT core
> > > code use platform_get_irq_optional().
> > >
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > ---
> > > v2-v3:
> > > * Fixed review comment pointed by Andy
> > >
> > > v1->v2
> > > * Simplified checking error code
> > > * Break loop earlier if no interrupts are seen
> > >
> > > v1: https://lkml.org/lkml/2021/12/18/163
> > > ---
> > >  drivers/thermal/rcar_thermal.c | 17 ++++++++++++-----
> > >  1 file changed, 12 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/thermal/rcar_thermal.c b/drivers/thermal/rcar_thermal.c
> > > index b49f04daaf47..e480f7290ccf 100644
> > > --- a/drivers/thermal/rcar_thermal.c
> > > +++ b/drivers/thermal/rcar_thermal.c
> > > @@ -445,7 +445,7 @@ static int rcar_thermal_probe(struct platform_device *pdev)
> > >       struct rcar_thermal_common *common;
> > >       struct rcar_thermal_priv *priv;
> > >       struct device *dev = &pdev->dev;
> > > -     struct resource *res, *irq;
> > > +     struct resource *res;
> > >       const struct rcar_thermal_chip *chip = of_device_get_match_data(dev);
> > >       int mres = 0;
> > >       int i;
> > > @@ -467,9 +467,16 @@ static int rcar_thermal_probe(struct platform_device *pdev)
> > >       pm_runtime_get_sync(dev);
> > >
> > >       for (i = 0; i < chip->nirqs; i++) {
> > > -             irq = platform_get_resource(pdev, IORESOURCE_IRQ, i);
> > > -             if (!irq)
> > > -                     continue;
> > > +             int irq;
> > > +
> > > +             irq = platform_get_irq_optional(pdev, i);
> > > +             if (irq < 0 && irq != -ENXIO) {
> > > +                     ret = irq;
> > > +                     goto error_unregister;
> > > +             }
> > > +             if (!irq || irq == -ENXIO)
> > > +                     break;
> >
> > This do not look correct and differs form v1.
> >
> > In the old code if we can't get an IRQ the loop is continued. This is
> > used to detect if interrupts are supported or not on the platform.  This
> > change will fail on all systems that don't describes interrupts in DT
> > while the driver can function without interrupts.
> >
> There are no non-DT users for this driver. Do you see this driver
> being used in a non-DT environment in near future?

No, maybe I was unclear sorry about that. What I intended to say was 
that this change will break platforms that that make use of this driver 
but do not describe interrupts in its DT description. As with this 
change not describing interrupts is consider an error.

For example checkout thermal@...48000 in arch/arm/boot/dts/r8a7779.dtsi.

> 
> > Is there a reason you wish to do this change in addition to the switch
> > to platform_get_irq_optional()? If so I think that should be done in a
> > separate patch.
> >
> No other reason, It was suggested by Gerrt too to use a break instead
> of continue in v1.

I think we need to keep the original behavior.

> 
> Cheers,
> Prabhakar

-- 
Kind Regards,
Niklas Söderlund