Message-ID: <20181005105506.neri7niyelz2ahc5@vireshk-i7>
Date:   Fri, 5 Oct 2018 16:25:06 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Taniya Das <tdas@...eaurora.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Stephen Boyd <sboyd@...nel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        devicetree@...r.kernel.org, robh@...nel.org,
        skannan@...eaurora.org, linux-arm-msm@...r.kernel.org,
        amit.kucheria@...aro.org, evgreen@...gle.com
Subject: Re: [PATCH v8 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq HW
 driver

On 23-09-18, 16:03, 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 | 354 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 366 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..43107ab
> --- /dev/null
> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
> @@ -0,0 +1,354 @@
> +// 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 LUT_MAX_ENTRIES			40U
> +#define CORE_COUNT_VAL(val)		(((val) & (GENMASK(18, 16))) >> 16)
> +#define LUT_ROW_SIZE			32
> +#define CLK_HW_DIV			2
> +
> +enum {
> +	REG_ENABLE,
> +	REG_LUT_TABLE,
> +	REG_PERF_STATE,
> +
> +	REG_ARRAY_SIZE,
> +};
> +
> +struct cpufreq_qcom {
> +	struct cpufreq_frequency_table *table;
> +	void __iomem *reg_bases[REG_ARRAY_SIZE];
> +	cpumask_t related_cpus;
> +	unsigned int max_cores;
> +	unsigned long xo_rate;
> +	unsigned long cpu_hw_rate;
> +};
> +
> +static const u16 cpufreq_qcom_std_offsets[REG_ARRAY_SIZE] = {
> +	[REG_ENABLE]		= 0x0,
> +	[REG_LUT_TABLE]		= 0x110,
> +	[REG_PERF_STATE]	= 0x920,
> +};
> +
> +static struct cpufreq_qcom *qcom_freq_domain_map[NR_CPUS];
> +
> +static int
> +qcom_cpufreq_hw_target_index(struct cpufreq_policy *policy,
> +			     unsigned int index)
> +{
> +	struct cpufreq_qcom *c = policy->driver_data;
> +
> +	writel_relaxed(index, c->reg_bases[REG_PERF_STATE]);
> +
> +	return 0;
> +}
> +
> +static unsigned int qcom_cpufreq_hw_get(unsigned int cpu)
> +{
> +	struct cpufreq_qcom *c;
> +	struct cpufreq_policy *policy;
> +	unsigned int index;
> +
> +	policy = cpufreq_cpu_get_raw(cpu);
> +	if (!policy)
> +		return 0;
> +
> +	c = policy->driver_data;
> +
> +	index = readl_relaxed(c->reg_bases[REG_PERF_STATE]);
> +	index = min(index, LUT_MAX_ENTRIES - 1);
> +
> +	return policy->freq_table[index].frequency;
> +}
> +
> +static unsigned int
> +qcom_cpufreq_hw_fast_switch(struct cpufreq_policy *policy,
> +			    unsigned int target_freq)
> +{
> +	struct cpufreq_qcom *c = policy->driver_data;
> +	int index;
> +
> +	index = policy->cached_resolved_idx;
> +	if (index < 0)
> +		return 0;
> +
> +	writel_relaxed(index, c->reg_bases[REG_PERF_STATE]);
> +
> +	return policy->freq_table[index].frequency;
> +}
> +
> +static int qcom_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
> +{
> +	struct cpufreq_qcom *c;
> +
> +	c = qcom_freq_domain_map[policy->cpu];
> +	if (!c) {
> +		pr_err("No scaling support for CPU%d\n", policy->cpu);
> +		return -ENODEV;
> +	}
> +
> +	cpumask_copy(policy->cpus, &c->related_cpus);
> +
> +	policy->fast_switch_possible = true;
> +	policy->freq_table = c->table;
> +	policy->driver_data = c;
> +
> +	return 0;
> +}
> +
> +static struct freq_attr *qcom_cpufreq_hw_attr[] = {
> +	&cpufreq_freq_attr_scaling_available_freqs,
> +	&cpufreq_freq_attr_scaling_boost_freqs,
> +	NULL
> +};
> +
> +static struct cpufreq_driver cpufreq_qcom_hw_driver = {
> +	.flags		= CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK |
> +			  CPUFREQ_HAVE_GOVERNOR_PER_POLICY,
> +	.verify		= cpufreq_generic_frequency_table_verify,
> +	.target_index	= qcom_cpufreq_hw_target_index,
> +	.get		= qcom_cpufreq_hw_get,
> +	.init		= qcom_cpufreq_hw_cpu_init,
> +	.fast_switch    = qcom_cpufreq_hw_fast_switch,
> +	.name		= "qcom-cpufreq-hw",
> +	.attr		= qcom_cpufreq_hw_attr,
> +	.boost_enabled	= true,
> +};
> +
> +static int qcom_cpufreq_hw_read_lut(struct platform_device *pdev,
> +				    struct cpufreq_qcom *c)
> +{
> +	struct device *dev = &pdev->dev;
> +	void __iomem *base;
> +	u32 data, src, lval, i, core_count, prev_cc, prev_freq, cur_freq;
> +
> +	c->table = devm_kcalloc(dev, LUT_MAX_ENTRIES + 1,
> +				sizeof(*c->table), GFP_KERNEL);
> +	if (!c->table)
> +		return -ENOMEM;
> +
> +	base = c->reg_bases[REG_LUT_TABLE];
> +
> +	for (i = 0; i < LUT_MAX_ENTRIES; i++) {
> +		data = readl_relaxed(base + i * LUT_ROW_SIZE);
> +		src = (data & GENMASK(31, 30)) >> 30;
> +		lval = data & GENMASK(7, 0);
> +		core_count = CORE_COUNT_VAL(data);
> +
> +		if (src)
> +			c->table[i].frequency = c->xo_rate * lval / 1000;
> +		else
> +			c->table[i].frequency = c->cpu_hw_rate / 1000;
> +
> +		cur_freq = c->table[i].frequency;
> +
> +		dev_dbg(dev, "index=%d freq=%d, core_count %d\n",
> +			i, c->table[i].frequency, core_count);
> +
> +		if (core_count != c->max_cores)
> +			cur_freq = CPUFREQ_ENTRY_INVALID;
> +
> +		/*
> +		 * Two of the same frequencies with the same core counts means
> +		 * end of table.
> +		 */
> +		if (i > 0 && c->table[i - 1].frequency ==
> +		   c->table[i].frequency && prev_cc == core_count) {
> +			struct cpufreq_frequency_table *prev = &c->table[i - 1];
> +
> +			if (prev_freq == CPUFREQ_ENTRY_INVALID)
> +				prev->flags = CPUFREQ_BOOST_FREQ;
> +			break;
> +		}
> +		prev_cc = core_count;
> +		prev_freq = cur_freq;
> +	}

The logic here always surprises me, why does the firmware keeps the
table this way instead of simplifying it  ?

> +
> +	c->table[i].frequency = CPUFREQ_TABLE_END;
> +
> +	return 0;
> +}
> +
> +static int qcom_get_related_cpus(int index, struct cpumask *m)
> +{
> +	struct device_node *cpu_np;
> +	struct of_phandle_args args;
> +	int cpu, ret;
> +
> +	for_each_possible_cpu(cpu) {
> +		cpu_np = of_cpu_device_node_get(cpu);
> +		if (!cpu_np)
> +			continue;
> +		of_node_put(cpu_np);

Heh, you can't do that here :)

> +
> +		ret = of_parse_phandle_with_args(cpu_np, "qcom,freq-domain",

As this code still needs to use the same pointer. It is possible that
the memory associated with cpu_np gets freed as soon as you call
of_node_put() on that. You should call of_node_put() anytime after
this routine is called.

> +				"#freq-domain-cells", 0, &args);
> +		if (ret < 0)
> +			continue;
> +
> +		if (index == args.args[0])
> +			cpumask_set_cpu(cpu, m);
> +	}
> +
> +	return 0;
> +}
> +
> +static int qcom_cpu_resources_init(struct platform_device *pdev,
> +				   unsigned int cpu, int index,
> +				   unsigned long xo_rate,
> +				   unsigned long cpu_hw_rate)
> +{
> +	struct cpufreq_qcom *c;
> +	struct resource *res;
> +	struct device *dev = &pdev->dev;
> +	const u16 *offsets;
> +	int ret, i, 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;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, index);
> +	base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	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, "Domain-%d cpufreq hardware not enabled\n", index);
> +		return -ENODEV;
> +	}
> +
> +	ret = qcom_get_related_cpus(index, &c->related_cpus);
> +	if (ret) {
> +		dev_err(dev, "Domain-%d failed to get related CPUs\n", index);
> +		return ret;
> +	}
> +
> +	c->max_cores = cpumask_weight(&c->related_cpus);
> +	if (!c->max_cores)
> +		return -ENOENT;
> +
> +	c->xo_rate = xo_rate;
> +	c->cpu_hw_rate = cpu_hw_rate;
> +
> +	ret = qcom_cpufreq_hw_read_lut(pdev, c);
> +	if (ret) {
> +		dev_err(dev, "Domain-%d failed to read LUT\n", index);
> +		return ret;
> +	}
> +
> +	for_each_cpu(cpu_r, &c->related_cpus)
> +		qcom_freq_domain_map[cpu_r] = c;
> +
> +	return 0;
> +}
> +
> +static int qcom_resources_init(struct platform_device *pdev)
> +{
> +	struct device_node *cpu_np;
> +	struct of_phandle_args args;
> +	struct clk *clk;
> +	unsigned int cpu;
> +	unsigned long xo_rate, cpu_hw_rate;
> +	int ret;
> +
> +	clk = devm_clk_get(&pdev->dev, "xo");
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	xo_rate = clk_get_rate(clk);
> +
> +	devm_clk_put(&pdev->dev, clk);

Why use devm_ variants if you want to put the clock anyway ?

> +	clk = devm_clk_get(&pdev->dev, "cpu_clk");
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	cpu_hw_rate = clk_get_rate(clk) / CLK_HW_DIV;
> +
> +	devm_clk_put(&pdev->dev, clk);

same here.

> +
> +	for_each_possible_cpu(cpu) {
> +		cpu_np = of_cpu_device_node_get(cpu);

Where is the of_node_put() corresponding to this ?

> +		if (!cpu_np) {
> +			dev_dbg(&pdev->dev, "Failed to get cpu %d device\n",
> +				cpu);
> +			continue;
> +		}
> +
> +		ret = of_parse_phandle_with_args(cpu_np, "qcom,freq-domain",
> +				"#freq-domain-cells", 0, &args);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = qcom_cpu_resources_init(pdev, cpu, args.args[0],
> +					      xo_rate, cpu_hw_rate);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int qcom_cpufreq_hw_driver_probe(struct platform_device *pdev)
> +{
> +	int rc;
> +
> +	/* Get the bases of cpufreq for domains */
> +	rc = qcom_resources_init(pdev);
> +	if (rc) {
> +		dev_err(&pdev->dev, "CPUFreq resource init failed\n");
> +		return rc;
> +	}
> +
> +	rc = cpufreq_register_driver(&cpufreq_qcom_hw_driver);
> +	if (rc) {
> +		dev_err(&pdev->dev, "CPUFreq HW driver failed to register\n");
> +		return rc;
> +	}
> +
> +	dev_dbg(&pdev->dev, "QCOM CPUFreq HW driver initialized\n");
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id qcom_cpufreq_hw_match[] = {
> +	{ .compatible = "qcom,cpufreq-hw", .data = &cpufreq_qcom_std_offsets },
> +	{}
> +};
> +
> +static struct platform_driver qcom_cpufreq_hw_driver = {
> +	.probe = qcom_cpufreq_hw_driver_probe,
> +	.driver = {
> +		.name = "qcom-cpufreq-hw",
> +		.of_match_table = qcom_cpufreq_hw_match,
> +	},
> +};
> +
> +static int __init qcom_cpufreq_hw_init(void)
> +{
> +	return platform_driver_register(&qcom_cpufreq_hw_driver);
> +}
> +subsys_initcall(qcom_cpufreq_hw_init);
> +
> +MODULE_DESCRIPTION("QCOM firmware-based CPU Frequency driver");
> --
> Qualcomm INDIA, on behalf of Qualcomm Innovation Center, Inc.is a member
> of the Code Aurora Forum, hosted by the  Linux Foundation.

-- 
viresh

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