linux-kernel - Re: [PATCH v3 2/4] irqchip/qcom-pdc: Switch to using IRQCHIP_PLATFORM

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Date:   Wed, 5 Aug 2020 18:24:50 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <maz@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        lkml <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Hanks Chen <hanks.chen@...iatek.com>,
        CC Hwang <cc.hwang@...iatek.com>,
        Loda Chou <loda.chou@...iatek.com>
Subject: Re: [PATCH v3 2/4] irqchip/qcom-pdc: Switch to using
 IRQCHIP_PLATFORM_DRIVER helper macros

On Wed, Aug 5, 2020 at 1:19 PM Saravana Kannan <saravanak@...gle.com> wrote:
> On Wed, Aug 5, 2020 at 12:44 AM John Stultz <john.stultz@...aro.org> wrote:
> > On Fri, Jul 17, 2020 at 5:06 PM Saravana Kannan <saravanak@...gle.com> wrote:
> > >
> > > Switch the driver to use the helper macros. In addition to reducing the
> > > number of lines, this also adds module unload protection (if the driver
> > > is compiled as a module) by switching from module_platform_driver to
> > > builtin_platform_driver.
> > >
> > > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> > > ---
> > >  drivers/irqchip/qcom-pdc.c | 26 +++-----------------------
> > >  1 file changed, 3 insertions(+), 23 deletions(-)
> > >
> > > diff --git a/drivers/irqchip/qcom-pdc.c b/drivers/irqchip/qcom-pdc.c
> > > index 5b624e3295e4..c1c5dfad57cc 100644
> > > --- a/drivers/irqchip/qcom-pdc.c
> > > +++ b/drivers/irqchip/qcom-pdc.c
> > > @@ -432,28 +432,8 @@ static int qcom_pdc_init(struct device_node *node, struct device_node *parent)
> > >         return ret;
> > >  }
> > >
> > > -static int qcom_pdc_probe(struct platform_device *pdev)
> > > -{
> > > -       struct device_node *np = pdev->dev.of_node;
> > > -       struct device_node *parent = of_irq_find_parent(np);
> > > -
> > > -       return qcom_pdc_init(np, parent);
> > > -}
> > > -
> > > -static const struct of_device_id qcom_pdc_match_table[] = {
> > > -       { .compatible = "qcom,pdc" },
> > > -       {}
> > > -};
> > > -MODULE_DEVICE_TABLE(of, qcom_pdc_match_table);
> > > -
> > > -static struct platform_driver qcom_pdc_driver = {
> > > -       .probe = qcom_pdc_probe,
> > > -       .driver = {
> > > -               .name = "qcom-pdc",
> > > -               .of_match_table = qcom_pdc_match_table,
> > > -               .suppress_bind_attrs = true,
> > > -       },
> > > -};
> > > -module_platform_driver(qcom_pdc_driver);
> > > +IRQCHIP_PLATFORM_DRIVER_BEGIN(qcom_pdc)
> > > +IRQCHIP_MATCH("qcom,pdc", qcom_pdc_init)
> > > +IRQCHIP_PLATFORM_DRIVER_END(qcom_pdc)
> > >  MODULE_DESCRIPTION("Qualcomm Technologies, Inc. Power Domain Controller");
> > >  MODULE_LICENSE("GPL v2");
> >
> > <sigh>
> > So this is where I bashfully admit I didn't get a chance to try this
> > patch series out, as I had success with a much older version of
> > Saravana's macro magic.
> >
> > But unfortunately, now that this has landed in mainline, I'm seeing
> > boot regressions on db845c. :( This is in the non-modular case,
> > building the driver in.
>
> Does that mean the modular version is working? Or you haven't tried
> that yet? I'll wait for your reply before I try to fix it. I don't
> have the hardware, but it should be easy to guess this issue looking
> at the code delta.

I've not yet tested with modules with your patch.

> The only significant change from what your probe function is doing is
> this snippet. But it'd be surprising if this only affects the builtin
> case.
>
> + if (par_np == np)
> +         par_np = NULL;
> +
> + /*
> + * If there's a parent interrupt controller and  none of the parent irq
> + * domains have been registered, that means the parent interrupt
> + * controller has not been initialized yet.  it's not time for this
> + * interrupt controller to initialize. So, defer probe of this
> + * interrupt controller. The actual initialization callback of this
> + * interrupt controller can check for specific domains as necessary.
> + */
> + if (par_np && !irq_find_matching_host(np, DOMAIN_BUS_ANY))
> +         return -EPROBE_DEFER;

Yep. We're getting caught on the irq_find_matching_host() check. I'm a
little lost as when I look at the qcom,pdc node in the dtsi its not
under a parent controller (instead the soc node).
Not sure if that's an issue in the dtsi or if par_np check needs to
ignore the soc node and pass null?

thanks
-john