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Date: Mon, 24 Sep 2018 10:02:00 -0700
From: Matthias Kaehlcke <mka@...omium.org>
To: Taniya Das <tdas@...eaurora.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Viresh Kumar <viresh.kumar@...aro.org>,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
Stephen Boyd <sboyd@...nel.org>,
Rajendra Nayak <rnayak@...eaurora.org>,
Amit Nischal <anischal@...eaurora.org>,
devicetree@...r.kernel.org, robh@...nel.org,
skannan@...eaurora.org, amit.kucheria@...aro.org,
evgreen@...gle.com
Subject: Re: [PATCH v7 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq HW
driver
On Sun, Sep 23, 2018 at 03:10:55PM +0530, Taniya Das wrote:
> Hello Matthias,
>
> Thanks for your review comments.
>
> On 8/29/2018 11:31 PM, Matthias Kaehlcke wrote:
> > Hi Taniya,
> >
> > On Tue, Jul 24, 2018 at 04:12:50PM +0530, Taniya Das wrote:
> > > The CPUfreq HW present in some QCOM chipsets offloads the steps necessary
> > > for changing the frequency of CPUs. The driver implements the cpufreq
> > > driver interface for this hardware engine.
> > >
> > > Signed-off-by: Saravana Kannan <skannan@...eaurora.org>
> > > Signed-off-by: Taniya Das <tdas@...eaurora.org>
> > > ---
> > > drivers/cpufreq/Kconfig.arm | 11 ++
> > > drivers/cpufreq/Makefile | 1 +
> > > drivers/cpufreq/qcom-cpufreq-hw.c | 348 ++++++++++++++++++++++++++++++++++++++
> > > 3 files changed, 360 insertions(+)
> > > create mode 100644 drivers/cpufreq/qcom-cpufreq-hw.c
> > >
> > > diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> > > index 0cd8eb7..93a9d72 100644
> > > --- a/drivers/cpufreq/Kconfig.arm
> > > +++ b/drivers/cpufreq/Kconfig.arm
> > > @@ -298,3 +298,14 @@ config ARM_PXA2xx_CPUFREQ
> > > This add the CPUFreq driver support for Intel PXA2xx SOCs.
> > >
> > > If in doubt, say N.
> > > +
> > > +config ARM_QCOM_CPUFREQ_HW
> > > + bool "QCOM CPUFreq HW driver"
> > > + depends on ARCH_QCOM
> > > + help
> > > + Support for the CPUFreq HW driver.
> > > + Some QCOM chipsets have a HW engine to offload the steps
> > > + necessary for changing the frequency of the CPUs. Firmware loaded
> > > + in this engine exposes a programming interface to the OS.
> > > + The driver implements the cpufreq interface for this HW engine.
> > > + Say Y if you want to support CPUFreq HW.
> > > diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
> > > index c1ffeab..ca48a1d 100644
> > > --- a/drivers/cpufreq/Makefile
> > > +++ b/drivers/cpufreq/Makefile
> > > @@ -85,6 +85,7 @@ obj-$(CONFIG_ARM_TEGRA124_CPUFREQ) += tegra124-cpufreq.o
> > > obj-$(CONFIG_ARM_TEGRA186_CPUFREQ) += tegra186-cpufreq.o
> > > obj-$(CONFIG_ARM_TI_CPUFREQ) += ti-cpufreq.o
> > > obj-$(CONFIG_ARM_VEXPRESS_SPC_CPUFREQ) += vexpress-spc-cpufreq.o
> > > +obj-$(CONFIG_ARM_QCOM_CPUFREQ_HW) += qcom-cpufreq-hw.o
> > >
> > >
> > > ##################################################################################
> > > diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
> > > new file mode 100644
> > > index 0000000..ea8f7d1
> > > --- /dev/null
> > > +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
> > > @@ -0,0 +1,348 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * Copyright (c) 2018, The Linux Foundation. All rights reserved.
> > > + */
> > > +
> > > +#include <linux/cpufreq.h>
> > > +#include <linux/init.h>
> > > +#include <linux/kernel.h>
> > > +#include <linux/module.h>
> > > +#include <linux/of_address.h>
> > > +#include <linux/of_platform.h>
> > > +
> > > +#define INIT_RATE 300000000UL
> > > +#define LUT_MAX_ENTRIES 40U
> > > +#define CORE_COUNT_VAL(val) (((val) & (GENMASK(18, 16))) >> 16)
> > > +#define LUT_ROW_SIZE 32
> > > +
> > > +enum {
> > > + REG_ENABLE,
> > > + REG_LUT_TABLE,
> > > + REG_PERF_STATE,
> > > +
> > > + REG_ARRAY_SIZE,
> > > +};
> > > +
> > > +struct cpufreq_qcom {
> > > + struct cpufreq_frequency_table *table;
> > > + struct device *dev;
> >
> > 'dev' is not used and can be removed.
> >
>
> Thanks, would remove in the next patch.
>
> > > ...
> > >
> > > +static int qcom_cpu_resources_init(struct platform_device *pdev,
> > > + struct device_node *np, unsigned int cpu,
> > > + unsigned long xo_rate)
> > > +{
> > > + struct cpufreq_qcom *c;
> > > + struct resource res;
> > > + struct device *dev = &pdev->dev;
> > > + const u16 *offsets;
> > > + int ret, i, cpu_first, cpu_r;
> > > + void __iomem *base;
> > > +
> > > + if (qcom_freq_domain_map[cpu])
> > > + return 0;
> > > +
> > > + c = devm_kzalloc(dev, sizeof(*c), GFP_KERNEL);
> > > + if (!c)
> > > + return -ENOMEM;
> > > +
> > > + offsets = of_device_get_match_data(&pdev->dev);
> > > + if (!offsets)
> > > + return -EINVAL;
> > > +
> > > + if (of_address_to_resource(np, 0, &res))
> > > + return -ENOMEM;
> > > +
> > > + base = devm_ioremap_resource(dev, &res);
> > > + if (!base)
> > > + return -ENOMEM;
> > > +
> > > + for (i = REG_ENABLE; i < REG_ARRAY_SIZE; i++)
> > > + c->reg_bases[i] = base + offsets[i];
> > > +
> > > + /* HW should be in enabled state to proceed */
> > > + if (!(readl_relaxed(c->reg_bases[REG_ENABLE]) & 0x1)) {
> > > + dev_err(dev, "%s cpufreq hardware not enabled\n", np->name);
> > > + return -ENODEV;
> > > + }
> > > +
> > > + ret = qcom_get_related_cpus(np, &c->related_cpus);
> > > + if (ret) {
> > > + dev_err(dev, "%s failed to get related CPUs\n", np->name);
> > > + return ret;
> > > + }
> > > +
> > > + c->max_cores = cpumask_weight(&c->related_cpus);
> > > + if (!c->max_cores)
> > > + return -ENOENT;
> > > +
> > > + c->xo_rate = xo_rate;
> > > +
> > > + ret = qcom_cpufreq_hw_read_lut(pdev, c);
> > > + if (ret) {
> > > + dev_err(dev, "%s failed to read LUT\n", np->name);
> > > + return ret;
> > > + }
> > > +
> > > + qcom_freq_domain_map[cpu] = c;
> > > +
> > > + /* Related CPUs */
> > > + cpu_first = cpumask_first(&c->related_cpus);
> > > +
> > > + for_each_cpu(cpu_r, &c->related_cpus) {
> > > + if (cpu_r != cpu_first)
> > > + qcom_freq_domain_map[cpu_r] =
> > > + qcom_freq_domain_map[cpu_first];
> > > + }
> >
> > The above ten lines could be simplified to:
> >
> > for_each_cpu(cpu_r, &c->related_cpus)
> > qcom_freq_domain_map[cpu_r] = c;
> >
>
> Would clean it up in the next patch.
>
> > > ...
> > >
> > > +static int __init qcom_cpufreq_hw_init(void)
> > > +{
> > > + return platform_driver_register(&qcom_cpufreq_hw_driver);
> > > +}
> > > +subsys_initcall(qcom_cpufreq_hw_init);
> >
> > Is subsys_initcall used for a particular reason? It will cause
> > problems when registering cooling devices, since the thermal device
> > class is initialized through an fs_initcall, which are executed
> > later.
> >
> > Most cpufreq drivers use module_init, device_initcall or
> > late_initcall, can't this driver use one of those?
> >
>
> We want the CPU to be scaling to the highest frequency at the
> earliest.
I guess you also want thermal management for the CPU. With the
subsys_initcall registration of cooling devices fails, as mentioned in
my earlier comment. Do you plan to defer the registration of cooling
devices?
Cheers
Matthias
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