linux-kernel - Re: [PATCH 4/4] cpufreq: add driver for Raspbery Pi

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Date:   Wed, 05 Jun 2019 11:12:25 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Eric Anholt <eric@...olt.net>, stefan.wahren@...e.com,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org, f.fainelli@...il.com,
        ptesarik@...e.com, sboyd@...nel.org, mturquette@...libre.com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        mbrugger@...e.de, ssuloev@...altech.com
Subject: Re: [PATCH 4/4] cpufreq: add driver for Raspbery Pi

Hi Eric,

On Tue, 2019-06-04 at 17:18 -0700, Eric Anholt wrote:
> Nicolas Saenz Julienne <nsaenzjulienne@...e.de> writes:
> 
> > Raspberry Pi's firmware offers and interface though which update it's
> > performance requirements. It allows us to request for specific runtime
> > frequencies, which the firmware might or might not respect, depending on
> > the firmware configuration and thermals.
> > 
> > As the maximum and minimum frequencies are configurable in the firmware
> > there is no way to know in advance their values. So the Raspberry Pi
> > cpufreq driver queries them, builds an opp frequency table to then
> > launch cpufreq-dt.
> > 
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> > ---
> > 
> > Changes since RFC:
> >   - Alphabetically ordered relevant stuff
> >   - Updated Kconfig to select firmware interface
> >   - Correctly unref clk_dev after use
> >   - Remove all opps on failure
> >   - Remove use of dev_pm_opp_set_sharing_cpus()
> > 
> >  drivers/cpufreq/Kconfig.arm           |  8 +++
> >  drivers/cpufreq/Makefile              |  1 +
> >  drivers/cpufreq/raspberrypi-cpufreq.c | 84 +++++++++++++++++++++++++++
> >  3 files changed, 93 insertions(+)
> >  create mode 100644 drivers/cpufreq/raspberrypi-cpufreq.c
> > 
> > diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> > index f8129edc145e..556d432cc826 100644
> > --- a/drivers/cpufreq/Kconfig.arm
> > +++ b/drivers/cpufreq/Kconfig.arm
> > @@ -133,6 +133,14 @@ config ARM_QCOM_CPUFREQ_HW
> >  	  The driver implements the cpufreq interface for this HW engine.
> >  	  Say Y if you want to support CPUFreq HW.
> >  
> > +config ARM_RASPBERRYPI_CPUFREQ
> > +	tristate "Raspberry Pi cpufreq support"
> > +	select RASPBERRYPI_FIRMWARE
> > +	help
> > +	  This adds the CPUFreq driver for Raspberry Pi
> > +
> > +	  If in doubt, say N.
> > +
> >  config ARM_S3C_CPUFREQ
> >  	bool
> >  	help
> > diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
> > index 689b26c6f949..121c1acb66c0 100644
> > --- a/drivers/cpufreq/Makefile
> > +++ b/drivers/cpufreq/Makefile
> > @@ -64,6 +64,7 @@ obj-$(CONFIG_ARM_PXA2xx_CPUFREQ)	+= pxa2xx-cpufreq.o
> >  obj-$(CONFIG_PXA3xx)			+= pxa3xx-cpufreq.o
> >  obj-$(CONFIG_ARM_QCOM_CPUFREQ_HW)	+= qcom-cpufreq-hw.o
> >  obj-$(CONFIG_ARM_QCOM_CPUFREQ_KRYO)	+= qcom-cpufreq-kryo.o
> > +obj-$(CONFIG_ARM_RASPBERRYPI_CPUFREQ) 	+= raspberrypi-cpufreq.o
> >  obj-$(CONFIG_ARM_S3C2410_CPUFREQ)	+= s3c2410-cpufreq.o
> >  obj-$(CONFIG_ARM_S3C2412_CPUFREQ)	+= s3c2412-cpufreq.o
> >  obj-$(CONFIG_ARM_S3C2416_CPUFREQ)	+= s3c2416-cpufreq.o
> > diff --git a/drivers/cpufreq/raspberrypi-cpufreq.c
> > b/drivers/cpufreq/raspberrypi-cpufreq.c
> > new file mode 100644
> > index 000000000000..2b3a195a9d37
> > --- /dev/null
> > +++ b/drivers/cpufreq/raspberrypi-cpufreq.c
> > @@ -0,0 +1,84 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Raspberry Pi cpufreq driver
> > + *
> > + * Copyright (C) 2019, Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/cpu.h>
> > +#include <linux/cpufreq.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pm_opp.h>
> > +
> > +static const struct of_device_id machines[] __initconst = {
> > +	{ .compatible = "raspberrypi,3-model-b-plus" },
> > +	{ .compatible = "raspberrypi,3-model-b" },
> > +	{ .compatible = "raspberrypi,2-model-b" },
> > +	{ /* sentinel */ }
> > +};
> 
> I think I'd skip the compatible string check here.  The firmware's
> clock-management should be well-tested by folks playing with clocking in
> the downstream tree.  There aren't any firmware differences in the
> processing of these clock management packets, to my recollection.

Fair enough, I'll remove it.

> Other than that, I'm happy with the series and would give it my
> acked-by.

Thanks!

Regads,
Nicolas


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