linux-kernel - Re: [PATCH v4 3/3] arm64: dts: qcom: sc8280xp-x13s: model the PMU of the on-board wcn6855

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Message-ID: <CAMRc=MdXRj0oOxmn_tVKmtVQqKS0H_CGgMBhb6rAOmXz7Qxahg@mail.gmail.com>
Date: Fri, 4 Oct 2024 13:08:27 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Stephan Gerhold <stephan.gerhold@...aro.org>
Cc: Johan Hovold <johan@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Kalle Valo <kvalo@...nel.org>, linux-arm-msm@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, Steev Klimaszewski <steev@...i.org>
Subject: Re: [PATCH v4 3/3] arm64: dts: qcom: sc8280xp-x13s: model the PMU of
 the on-board wcn6855

On Fri, Oct 4, 2024 at 1:04 PM Stephan Gerhold
<stephan.gerhold@...aro.org> wrote:
>
> On Thu, Oct 03, 2024 at 05:16:59AM -0700, Bartosz Golaszewski wrote:
> > On Thu, 3 Oct 2024 13:38:35 +0200, Bartosz Golaszewski <brgl@...ev.pl> said:
> > > On Thu, Oct 3, 2024 at 1:07 PM Johan Hovold <johan@...nel.org> wrote:
> > >>
> > >> Without this patch I'm seeing an indefinite probe deferral with
> > >> 6.12-rc1:
> > >>
> > >>         platform 1c00000.pcie:pcie@0:wifi@0: deferred probe pending: pci-pwrctl-pwrseq: Failed to get the power sequencer
> > >>
> > >> Can you please look into that and make sure that the existing DT
> > >> continues to work without such warnings.
> > >>
> > >
> > > Ah, dammit, I missed the fact that X13s already has this node defined
> > > so PCI pwrctl will consume it and try to get the power sequencer
> > > handle. I'm wondering how to tackle it though... It will most likely
> > > require some kind of a driver quirk where we check if we have the PMU
> > > node and if not, then don't try to set up power sequencing. Any other
> > > ideas?
> > >
> >
> > This is untested but would it make sense?
> >
> > diff --git a/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c
> > b/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c
> > index a23a4312574b..071ee77c763d 100644
> > --- a/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c
> > +++ b/drivers/pci/pwrctl/pci-pwrctl-pwrseq.c
> > @@ -3,6 +3,7 @@
> >   * Copyright (C) 2024 Linaro Ltd.
> >   */
> >
> > +#include <linux/cleanup.h>
> >  #include <linux/device.h>
> >  #include <linux/mod_devicetable.h>
> >  #include <linux/module.h>
> > @@ -87,7 +88,31 @@ static struct platform_driver pci_pwrctl_pwrseq_driver = {
> >       },
> >       .probe = pci_pwrctl_pwrseq_probe,
> >  };
> > -module_platform_driver(pci_pwrctl_pwrseq_driver);
> > +
> > +static int __init pci_pwrctl_pwrseq_init(void)
> > +{
> > +     /*
> > +      * Old device trees for the Lenovo X13s have the "pci17cb,1103" node
> > +      * defined but don't use power sequencing yet. If we register this
> > +      * driver, it will match against this node and lead to emitting of
> > +      * a warning in the kernel log when we cannot get the power sequencing
> > +      * handle. Let's skip registering the platform driver if we're on X13s
> > +      * but don't have the PMU node.
> > +      */
> > +     if (of_machine_is_compatible("lenovo,thinkpad-x13s")) {
> > +             struct device_node *dn __free(device_node) =
> > +                     of_find_compatible_node(NULL, NULL, "qcom,wcn6855-pmu");
> > +             if (!dn)
> > +                     return 0;
> > +     }
> > +
> > +     return platform_driver_register(&pci_pwrctl_pwrseq_driver);
> > +}
> > +
> > +static void __exit pci_pwrctl_pwrseq_exit(void)
> > +{
> > +     platform_driver_unregister(&pci_pwrctl_pwrseq_driver);
> > +}
> >
> >  MODULE_AUTHOR("Bartosz Golaszewski <bartosz.golaszewski@...aro.org>");
> >  MODULE_DESCRIPTION("Generic PCI Power Control module for power
> > sequenced devices");
> >
> > X13s is the only platform that would use one of the compatibles supported by
> > this driver before power sequencing so it should be a one-off quirk.
> >
>
> I'm guessing the pci17cb,1107 node in x1e80100-lenovo-yoga-slim7x is
> also affected?
>
> Maybe you can check if the node has one of the -supply properties and
> return -ENODEV from pci_pwrctl_pwrseq_probe() otherwise?
>

Yeah, that may be a better solution I suppose.

Bart