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Date: Wed, 29 Aug 2018 11:01:22 -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
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.
> ...
>
> +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;
> ...
>
> +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?
Cheers
Matthias
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