Re: [PATCH v8 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq HW driver

Taniya Das <tdas@xxxxxxxxxxxxxx> · Thu, 11 Oct 2018 16:49:24 +0530

Hello Viresh,

Thanks for your review comments.

On 10/5/2018 4:25 PM, Viresh Kumar wrote:
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@xxxxxxxxxxxxxx>
Signed-off-by: Taniya Das <tdas@xxxxxxxxxxxxxx>
---
  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  ?


Unfortunately that is the only way to identify.

+
+	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 :)


Yes, I would take care to put it in the right place.

+
+		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 ?


Would move to non devm_ variants.

+	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");
--
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of the Code Aurora Forum, hosted by the  Linux Foundation.


--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation.

--






