Date:   Wed, 21 Nov 2018 10:41:06 -0800
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>,
        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 v10 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq
 HW driver

Hi Taniya,

thanks for respinning, a few nits inline.

On Wed, Nov 21, 2018 at 04:12:47PM +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 | 346 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 358 insertions(+)
>  create mode 100644 drivers/cpufreq/qcom-cpufreq-hw.c
> 
> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> index 4e1131e..688f102 100644
> --- a/drivers/cpufreq/Kconfig.arm
> +++ b/drivers/cpufreq/Kconfig.arm
> @@ -114,6 +114,17 @@ config ARM_QCOM_CPUFREQ_KRYO
> 
>  	  If in doubt, say N.
> 
> +config ARM_QCOM_CPUFREQ_HW
> +	tristate "QCOM CPUFreq HW driver"
> +	depends on ARCH_QCOM || COMPILE_TEST
> +	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.
> +
>  config ARM_S3C_CPUFREQ
>  	bool
>  	help
> diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
> index d5ee456..789b2e0 100644
> --- a/drivers/cpufreq/Makefile
> +++ b/drivers/cpufreq/Makefile
> @@ -62,6 +62,7 @@ obj-$(CONFIG_ARM_OMAP2PLUS_CPUFREQ)	+= omap-cpufreq.o
>  obj-$(CONFIG_ARM_PXA2xx_CPUFREQ)	+= pxa2xx-cpufreq.o
>  obj-$(CONFIG_PXA3xx)			+= pxa3xx-cpufreq.o
>  obj-$(CONFIG_ARM_QCOM_CPUFREQ_KRYO)	+= qcom-cpufreq-kryo.o
> +obj-$(CONFIG_ARM_QCOM_CPUFREQ_HW)	+= qcom-cpufreq-hw.o
>  obj-$(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/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
> new file mode 100644
> index 0000000..6390e85
> --- /dev/null
> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
> @@ -0,0 +1,346 @@
> +// 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
> +
> +/* Register offsets */
> +#define REG_ENABLE			0x0
> +#define REG_LUT_TABLE			0x110
> +#define REG_PERF_STATE			0x920
> +
> +struct cpufreq_qcom {
> +	struct cpufreq_frequency_table *table;
> +	void __iomem *perf_base;

nit: is this really a base address? It's the address of the perf state
register, right? Better name it 'perf_state_reg'/'reg_perf_state' or
similar (just 'perf_state' might be confusing, I'd expect a variable
with this name to hold a state, not an address).

> +	cpumask_t related_cpus;
> +	unsigned int max_cores;
> +	unsigned long xo_rate;
> +	unsigned long cpu_hw_rate;
> +};
> +
> +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->perf_base);
> +
> +	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->perf_base);
> +	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->perf_base);
> +
> +	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, void __iomem *base)
> +{
> +	struct device *dev = &pdev->dev;
> +	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;
> +
> +	for (i = 0; i < LUT_MAX_ENTRIES; i++) {
> +		data = readl_relaxed(base + REG_LUT_TABLE + 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;
> +	}
> +
> +	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;
> +
> +		ret = of_parse_phandle_with_args(cpu_np, "qcom,freq-domain",
> +						 "#freq-domain-cells", 0,
> +						  &args);
> +		of_node_put(cpu_np);
> +		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;
> +	void __iomem *base;
> +	int ret, cpu_r;
> +
> +	if (qcom_freq_domain_map[cpu])
> +		return 0;
> +
> +	c = devm_kzalloc(dev, sizeof(*c), GFP_KERNEL);
> +	if (!c)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, index);
> +	base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	/* HW should be in enabled state to proceed */
> +	if (!(readl_relaxed(base + 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;
> +	c->perf_base = base + REG_PERF_STATE;
> +
> +	ret = qcom_cpufreq_hw_read_lut(pdev, c, base);
> +	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 = clk_get(&pdev->dev, "xo");
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	xo_rate = clk_get_rate(clk);
> +
> +	clk_put(clk);
> +
> +	clk = clk_get(&pdev->dev, "gcc_cpuss_gpll0_clk_src");

As commented on the binding patch, I'm not sure if this is the correct
name for this clock input from the POV of this IP block. Just a doubt
at this point, I don't have/find the hardware documentation to suggest
something better.

> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	cpu_hw_rate = clk_get_rate(clk) / CLK_HW_DIV;
> +
> +	clk_put(clk);
> +
> +	for_each_possible_cpu(cpu) {
> +		cpu_np = of_cpu_device_node_get(cpu);
> +		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);
> +		of_node_put(cpu_np);
> +		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" },
> +	{}
> +};
> +
> +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);

I'm still not convinced that a subsys_initcall is needed (instead of
module_init or device_initcall), as mentioned in the review of v7
it causes problems when registering CPU cooling devices, but we can
also fix this when support for cooling devices is added ;-)

> +static void __exit qcom_cpufreq_hw_exit(void)
> +{
> +	cpufreq_unregister_driver(&cpufreq_qcom_hw_driver);
> +	platform_driver_unregister(&qcom_cpufreq_hw_driver);
> +}
> +module_exit(qcom_cpufreq_hw_exit);
> +
> +MODULE_DESCRIPTION("QTI CPUFREQ HW Driver");

nit: make it 'QCOM CPUFreq HW driver' for consistency?

Cheers

Matthias

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