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

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Message-ID: <159442366514.1987609.434612639050774557@swboyd.mtv.corp.google.com>
Date:   Fri, 10 Jul 2020 16:27:45 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     Marc Zyngier <maz@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Linus Walleij <linus.walleij@...aro.org>,
        Maulik Shah <mkshah@...eaurora.org>,
        Lina Iyer <ilina@...eaurora.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Todd Kjos <tkjos@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        iommu@...ts.linux-foundation.org, linux-gpio@...r.kernel.org
Subject: Re: [PATCH v2 3/5] irqchip: Allow QCOM_PDC to be loadable as a permanent module

Quoting John Stultz (2020-07-10 15:44:18)
> On Thu, Jul 9, 2020 at 11:02 PM Stephen Boyd <swboyd@...omium.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.