Re: [PATCH v2 3/5] irqchip: Allow QCOM_PDC to be loadable as a permanent module

From: Stephen Boyd <swboyd@chromium.org>
To: John Stultz <john.stultz@linaro.org>
Cc: Marc Zyngier <maz@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Andy Gross <agross@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Joerg Roedel <joro@8bytes.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jason Cooper <jason@lakedaemon.net>,
	Linus Walleij <linus.walleij@linaro.org>,
	Maulik Shah <mkshah@codeaurora.org>,
	Lina Iyer <ilina@codeaurora.org>,
	Saravana Kannan <saravanak@google.com>,
	Todd Kjos <tkjos@google.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	iommu@lists.linux-foundation.org, linux-gpio@vger.kernel.org
Subject: Re: [PATCH v2 3/5] irqchip: Allow QCOM_PDC to be loadable as a permanent module
Date: Fri, 10 Jul 2020 16:27:45 -0700	[thread overview]
Message-ID: <159442366514.1987609.434612639050774557@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <CALAqxLW14f4Gn6Q3b89X10y7=Zct2NJSgjagUqxez_bObcp42w@mail.gmail.com>

Quoting John Stultz (2020-07-10 15:44:18)
> On Thu, Jul 9, 2020 at 11:02 PM Stephen Boyd <swboyd@chromium.org> wrote:
> >
> > Does it work? I haven't looked in detail but I worry that the child
> > irqdomain (i.e. pinctrl-msm) would need to delay probing until this
> > parent irqdomain is registered. Or has the hierarchical irqdomain code
> > been updated to handle the parent child relationship and wait for things
> > to probe or be loaded?
> 
> So I can't say I know the underlying hardware particularly well, but
> I've been using this successfully on the Dragonboard 845c with both
> static builds as well as module enabled builds.
> And the same patch has been in the android-mainline and android-5.4
> kernels for a while without objections from QCOM.
> 
> As to the probe ordering question, Saravana can maybe speak in more
> detail if it's involved in this case but the fw_devlink code has
> addressed many of these sorts of ordering issues.
> However, I'm not sure if I'm lucking into the right probe order, as we
> have been able to boot android-mainline w/ both fw_devlink=on and
> fw_devlink=off (though in the =off case, we need
> deferred_probe_timeout=30 to give us a bit more time for modules to
> load after init starts).
> 

Ok I looked at the code (sorry for not checking earlier) and I see this in
msm_gpio_init()

        np = of_parse_phandle(pctrl->dev->of_node, "wakeup-parent", 0);
        if (np) {
                chip->irq.parent_domain = irq_find_matching_host(np,
                                                 DOMAIN_BUS_WAKEUP);
                of_node_put(np);
                if (!chip->irq.parent_domain)
                        return -EPROBE_DEFER;

so it looks like we'll probe defer the pinctrl driver until the pdc module
loads. Meaning it should work to have pinctrl builtin and pdc as a module.