Re: [PATCH v3 2/4] irqchip/qcom-pdc: Switch to using IRQCHIP_PLATFORM_DRIVER helper macros

From: Marc Zyngier <maz@kernel.org>
To: John Stultz <john.stultz@linaro.org>
Cc: Saravana Kannan <saravanak@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jason Cooper <jason@lakedaemon.net>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Andy Gross <agross@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Android Kernel Team <kernel-team@android.com>,
	lkml <linux-kernel@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-mediatek@lists.infradead.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Hanks Chen <hanks.chen@mediatek.com>,
	CC Hwang <cc.hwang@mediatek.com>,
	Loda Chou <loda.chou@mediatek.com>,
	steev@kali.org
Subject: Re: [PATCH v3 2/4] irqchip/qcom-pdc: Switch to using IRQCHIP_PLATFORM_DRIVER helper macros
Date: Thu, 06 Aug 2020 09:49:39 +0100	[thread overview]
Message-ID: <5e6124390b9e3e7f4d6f6decbdb669ca@kernel.org> (raw)
In-Reply-To: <CALAqxLUz6GTT96nO9igiWVwyaRs_xbO+=mySLm4BKX6-Uh90ZA@mail.gmail.com>

On 2020-08-06 02:24, John Stultz wrote:
> On Wed, Aug 5, 2020 at 1:19 PM Saravana Kannan <saravanak@google.com> 
> wrote:
>> On Wed, Aug 5, 2020 at 12:44 AM John Stultz <john.stultz@linaro.org> 
>> wrote:
>> > On Fri, Jul 17, 2020 at 5:06 PM Saravana Kannan <saravanak@google.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@google.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?

I think you have nailed it. This checks for a domain attached to
the driver we are about to probe, and this domain cannot possibly
exist. Instead, it is the *parent* this should check for, as we
depend on it for successful probing.

Can you please give this a go?

Thanks,

         M.

diff --git a/drivers/irqchip/irqchip.c b/drivers/irqchip/irqchip.c
index 1bb0e36c2bf3..d2341153e181 100644
--- a/drivers/irqchip/irqchip.c
+++ b/drivers/irqchip/irqchip.c
@@ -52,7 +52,7 @@ int platform_irqchip_probe(struct platform_device 
*pdev)
  	 * 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))
+	if (par_np && !irq_find_matching_host(par_np, DOMAIN_BUS_ANY))
  		return -EPROBE_DEFER;

  	return irq_init_cb(np, par_np);

-- 
Jazz is not dead. It just smells funny...
