linux-kernel - Re: [PATCH v3 1/3] soc: qcom: rpmpd: Allow RPMPD driver to be loaded as a module

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Date:   Tue, 14 Apr 2020 15:32:46 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>, Todd Kjos <tkjos@...gle.com>,
        Saravana Kannan <saravanak@...gle.com>,
        Andy Gross <agross@...nel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] soc: qcom: rpmpd: Allow RPMPD driver to be loaded
 as a module

On Tue 14 Apr 15:24 PDT 2020, John Stultz wrote:

> On Tue, Apr 14, 2020 at 3:21 PM Bjorn Andersson
> <bjorn.andersson@...aro.org> wrote:
> >
> > On Thu 26 Mar 15:44 PDT 2020, John Stultz wrote:
> >
> > > This patch allow the rpmpd driver to be loaded as a permenent
> > > module. Meaning it can be loaded from a module, but then cannot
> > > be unloaded.
> > >
> > > Ideally, it would include a remove hook and related logic, but
> > > apparently the genpd code isn't able to track usage and cleaning
> > > things up? (See: https://lkml.org/lkml/2019/1/24/38)
> > >
> > > So making it a permenent module at least improves things slightly
> > > over requiring it to be a built in driver.
> > >
> > > Feedback would be appreciated!
> > >
> > > Cc: Todd Kjos <tkjos@...gle.com>
> > > Cc: Saravana Kannan <saravanak@...gle.com>
> > > Cc: Andy Gross <agross@...nel.org>
> > > Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> > > Cc: Rajendra Nayak <rnayak@...eaurora.org>
> > > Cc: linux-arm-msm@...r.kernel.org
> > > Acked-by: Saravana Kannan <saravanak@...gle.com>
> > > Signed-off-by: John Stultz <john.stultz@...aro.org>
> > > ---
> > > v2:
> > > * Fix MODULE_LICENSE to be GPL v2 as suggested by Bjorn
> > > * Leave initcall as core_initcall, since that switches to module_initcall
> > >   only when built as a module, also suggested by Bjorn
> > > * Add module tags taken from Rajendra's earlier patch
> > > ---
> > >  drivers/soc/qcom/Kconfig | 4 ++--
> > >  drivers/soc/qcom/rpmpd.c | 6 ++++++
> > >  2 files changed, 8 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
> > > index d0a73e76d563..af774555b9d2 100644
> > > --- a/drivers/soc/qcom/Kconfig
> > > +++ b/drivers/soc/qcom/Kconfig
> > > @@ -123,8 +123,8 @@ config QCOM_RPMHPD
> > >         for the voltage rail.
> > >
> > >  config QCOM_RPMPD
> > > -     bool "Qualcomm RPM Power domain driver"
> > > -     depends on QCOM_SMD_RPM=y
> > > +     tristate "Qualcomm RPM Power domain driver"
> > > +     depends on QCOM_SMD_RPM
> > >       help
> > >         QCOM RPM Power domain driver to support power-domains with
> > >         performance states. The driver communicates a performance state
> > > diff --git a/drivers/soc/qcom/rpmpd.c b/drivers/soc/qcom/rpmpd.c
> > > index 2b1834c5609a..22fe94c03e79 100644
> > > --- a/drivers/soc/qcom/rpmpd.c
> > > +++ b/drivers/soc/qcom/rpmpd.c
> > > @@ -5,6 +5,7 @@
> > >  #include <linux/init.h>
> > >  #include <linux/kernel.h>
> > >  #include <linux/mutex.h>
> > > +#include <linux/module.h>
> >
> > module comes before mutex in the alphabet.
> 
> :) Thanks for catching that.
> 
> > >  #include <linux/pm_domain.h>
> > >  #include <linux/of.h>
> > >  #include <linux/of_device.h>
> > > @@ -226,6 +227,7 @@ static const struct of_device_id rpmpd_match_table[] = {
> > >       { .compatible = "qcom,qcs404-rpmpd", .data = &qcs404_desc },
> > >       { }
> > >  };
> > > +MODULE_DEVICE_TABLE(of, rpmpd_match_table);
> > >
> > >  static int rpmpd_send_enable(struct rpmpd *pd, bool enable)
> > >  {
> > > @@ -422,3 +424,7 @@ static int __init rpmpd_init(void)
> > >       return platform_driver_register(&rpmpd_driver);
> > >  }
> > >  core_initcall(rpmpd_init);
> > > +
> > > +MODULE_DESCRIPTION("Qualcomm Technologies, Inc. RPM Power Domain Driver");
> > > +MODULE_LICENSE("GPL v2");
> > > +MODULE_ALIAS("platform:qcom-rpmpd");
> >
> > Is there any reason for this alias?
> >
> > The module will be automatically loaded based on compatible and the
> > MODULE_DEVICE_TABLE() information above, and for ACPI would need a
> > similar acpi_device_id table.
> 
> I pulled it in from Rajendra's earlier patch. I'm ok to drop it though.
> 
> I'll fix these up and respin. Thanks for the review!
> 

No worries, I'll fix these two things and apply the patch. Just wanted
to check if I was missing something.

Regards,
Bjorn