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Subject[PATCH v6 2/2] cpufreq: brcmstb-cpufreq: CPUfreq driver for older Broadcom STB SoCs
Date
From: Markus Mayer <mmayer@broadcom.com>

This CPUfreq driver provides basic frequency scaling for older Broadcom
STB SoCs that do not use AVS firmware with DVFS support. There is no
support for voltage scaling.

Signed-off-by: Markus Mayer <mmayer@broadcom.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
---
drivers/cpufreq/Kconfig.arm | 12 ++
drivers/cpufreq/Makefile | 1 +
drivers/cpufreq/brcmstb-cpufreq.c | 377 ++++++++++++++++++++++++++++++++++++++
3 files changed, 390 insertions(+)
create mode 100644 drivers/cpufreq/brcmstb-cpufreq.c

diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 920c469..36422af 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -33,6 +33,18 @@ config ARM_BRCMSTB_AVS_CPUFREQ_DEBUG

If in doubt, say N.

+config ARM_BRCMSTB_CPUFREQ
+ tristate "Broadcom STB CPUfreq driver"
+ depends on ARCH_BRCMSTB || COMPILE_TEST
+ default y
+ help
+ Some Broadcom SoCs offer multiple operating frequencies that CPUfreq
+ can take advantage of to improve energy efficiency.
+
+ Say Y, if you have a supported Broadcom SoC. If your Broadcom SoC
+ has AVS firmware with support for frequency and voltage scaling,
+ say N here and enable ARM_BRCMSTB_AVS_CPUFREQ instead.
+
config ARM_DT_BL_CPUFREQ
tristate "Generic probing via DT for ARM big LITTLE CPUfreq driver"
depends on ARM_BIG_LITTLE_CPUFREQ && OF
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 1e46c39..23700aa 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -52,6 +52,7 @@ obj-$(CONFIG_ARM_BIG_LITTLE_CPUFREQ) += arm_big_little.o
obj-$(CONFIG_ARM_DT_BL_CPUFREQ) += arm_big_little_dt.o

obj-$(CONFIG_ARM_BRCMSTB_AVS_CPUFREQ) += brcmstb-avs-cpufreq.o
+obj-$(CONFIG_ARM_BRCMSTB_CPUFREQ) += brcmstb-cpufreq.o
obj-$(CONFIG_ARCH_DAVINCI) += davinci-cpufreq.o
obj-$(CONFIG_UX500_SOC_DB8500) += dbx500-cpufreq.o
obj-$(CONFIG_ARM_EXYNOS5440_CPUFREQ) += exynos5440-cpufreq.o
diff --git a/drivers/cpufreq/brcmstb-cpufreq.c b/drivers/cpufreq/brcmstb-cpufreq.c
new file mode 100644
index 0000000..8849d56
--- /dev/null
+++ b/drivers/cpufreq/brcmstb-cpufreq.c
@@ -0,0 +1,377 @@
+/*
+ * CPU frequency scaling for Broadcom set top box SoCs
+ *
+ * Copyright (c) 2016-17 Broadcom
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/cpufreq.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+
+#define BRCMSTB_CPUFREQ_PREFIX "brcmstb"
+#define BRCMSTB_CPUFREQ_NAME BRCMSTB_CPUFREQ_PREFIX "-cpufreq"
+
+/* We search for these compatible strings. */
+#define BRCMSTB_DT_CPU_CLK_CTRL "brcm,brcmstb-cpu-clk-div"
+#define BRCMSTB_DT_MEMC_DDR "brcm,brcmstb-memc-ddr"
+#define BRCM_AVS_CPU_DATA "brcm,avs-cpu-data-mem"
+
+/*
+ * We also need a few clocks in device tree. They are referenced in the
+ * brcm,brcmstb-cpu-clk-div node in device tree, so we can look them up.
+ */
+#define BRCMSTB_CLK_MDIV_CH0 "cpu_mdiv_ch0"
+#define BRCMSTB_CLK_NDIV_INT "cpu_ndiv_int"
+#define BRCMSTB_CLK_SW_SCB "sw_scb"
+
+#define BRCMSTB_TBL_SAFE_MODE BIT(0)
+#define BRCMSTB_REG_SAFE_MODE BIT(4)
+
+#define TRANSITION_LATENCY (25 * 1000) /* 25 us */
+
+/* This is as low as we'll go in the frequency table. */
+#define MIN_CPU_FREQ (100 * 1000) /* in kHz */
+
+struct private_data {
+ void __iomem *cpu_clk_ctrl_reg;
+ struct clk *mdiv_clk;
+ struct clk *ndiv_clk;
+ struct clk *sw_scb_clk;
+ struct device *dev;
+};
+
+/* Count the active memory controllers in the system. */
+static int count_memory_controllers(void)
+{
+ struct device_node *np = NULL;
+ int i = 0;
+
+ do {
+ np = of_find_compatible_node(np, NULL, BRCMSTB_DT_MEMC_DDR);
+ if (of_device_is_available(np))
+ i++;
+ of_node_put(np);
+ } while (np);
+
+ return i;
+}
+
+static void get_frequencies(const struct cpufreq_policy *policy,
+ unsigned int *vco_freq, unsigned int *cpu_freq,
+ unsigned int *scb_freq)
+{
+ struct private_data *priv = policy->driver_data;
+
+ /* return frequencies in kHz */
+ *vco_freq = clk_get_rate(priv->ndiv_clk) / 1000;
+ *cpu_freq = clk_get_rate(priv->mdiv_clk) / 1000;
+ *scb_freq = clk_get_rate(priv->sw_scb_clk) / 1000;
+}
+
+/*
+ * Safe mode: When set, the CPU's bus unit is being throttled. This is done to
+ * avoid buffer overflows when the CPU-to-bus-clock ratio is low.
+ *
+ * The formula as to what constitutes a low CPU-to-bus-clock ratio takes into
+ * account the number of memory controllers active in the system and the SCB
+ * frequency. More memory controllers means safe mode is required starting at
+ * higher frequencies.
+ *
+ * For 1 memory controller, cpu_freq/scb_freq must be greater than or equal to
+ * 2 to not require safe mode.
+ *
+ * For 2 or 3 memory controllers, cpu_freq/scb_freq must be greater than or
+ * equal 3 to not require safe mode.
+ */
+
+static int freq_requires_safe_mode(unsigned int cpu_freq, unsigned int scb_freq,
+ int num_memc)
+{
+ unsigned int safe_ratio;
+
+ switch (num_memc) {
+ case 1:
+ safe_ratio = 2;
+ break;
+ case 2:
+ case 3:
+ safe_ratio = 3;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return ((cpu_freq / scb_freq) < safe_ratio);
+}
+
+static struct cpufreq_frequency_table *
+brcmstb_get_freq_table(const struct cpufreq_policy *policy)
+{
+ unsigned int cpu_freq, vco_freq, scb_freq, mdiv, init_mdiv, f;
+ struct cpufreq_frequency_table *table;
+ struct private_data *priv;
+ int num_memc, ret;
+ unsigned int i = 0;
+
+ priv = policy->driver_data;
+ num_memc = count_memory_controllers();
+ get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
+
+ /* Calculate the initial mdiv value. We'll increment mdiv from here. */
+ init_mdiv = vco_freq / cpu_freq;
+
+ /* Count how many frequencies we'll offer. */
+ f = cpu_freq;
+ for (mdiv = init_mdiv; f >= MIN_CPU_FREQ; mdiv++, f = vco_freq / mdiv) {
+ /* We only want to use "whole" MHz. */
+ if ((f % 1000) == 0)
+ i++;
+ }
+
+ table = devm_kzalloc(priv->dev, (i + 1) * sizeof(*table), GFP_KERNEL);
+ if (!table)
+ return ERR_PTR(-ENOMEM);
+
+ /* Now, fill the table. */
+ f = cpu_freq;
+ i = 0;
+ for (mdiv = init_mdiv; f >= MIN_CPU_FREQ; mdiv++, f = vco_freq / mdiv) {
+ if ((f % 1000) == 0) {
+ table[i].frequency = f;
+ ret = freq_requires_safe_mode(f, scb_freq, num_memc);
+ if (ret < 0)
+ return ERR_PTR(ret);
+ if (ret > 0)
+ table[i].driver_data |= BRCMSTB_TBL_SAFE_MODE;
+ i++;
+ }
+ }
+ table[i].frequency = CPUFREQ_TABLE_END;
+
+ return table;
+}
+
+static int brcmstb_target_index(struct cpufreq_policy *policy,
+ unsigned int index)
+{
+ struct cpufreq_frequency_table *entry;
+ struct private_data *priv;
+ int ret, safe_mode_needed;
+ u32 reg;
+
+ priv = policy->driver_data;
+ entry = &policy->freq_table[index];
+ safe_mode_needed = entry->driver_data & BRCMSTB_TBL_SAFE_MODE;
+
+ reg = readl(priv->cpu_clk_ctrl_reg);
+ if (safe_mode_needed && !(reg & BRCMSTB_REG_SAFE_MODE)) {
+ reg |= BRCMSTB_REG_SAFE_MODE;
+ writel(reg, priv->cpu_clk_ctrl_reg);
+ }
+ ret = clk_set_rate(policy->clk, entry->frequency * 1000);
+ if (!ret && !safe_mode_needed && (reg & BRCMSTB_REG_SAFE_MODE)) {
+ reg &= ~BRCMSTB_REG_SAFE_MODE;
+ writel(reg, priv->cpu_clk_ctrl_reg);
+ }
+
+ return ret;
+}
+
+/*
+ * All initialization code that we only want to execute once goes here. Setup
+ * code that can be re-tried on every core (if it failed before) can go into
+ * brcmstb_cpufreq_init().
+ */
+static int brcmstb_prepare_init(struct platform_device *pdev)
+{
+ struct private_data *priv;
+ struct resource *res;
+ struct device *dev;
+
+ /*
+ * If the BRCM STB AVS CPUfreq driver is supported, we bail, so that
+ * the more modern approach implementing DVFS in firmware can be used.
+ */
+ if (IS_ENABLED(CONFIG_ARM_BRCMSTB_AVS_CPUFREQ)) {
+ struct device_node *np;
+
+ np = of_find_compatible_node(NULL, NULL, BRCM_AVS_CPU_DATA);
+ if (np) {
+ of_node_put(np);
+ return -ENXIO;
+ }
+ }
+
+ dev = &pdev->dev;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ priv->cpu_clk_ctrl_reg = devm_ioremap_resource(dev, res);
+ if (IS_ERR(priv->cpu_clk_ctrl_reg)) {
+ dev_err(dev, "couldn't map DT entry %s\n",
+ BRCMSTB_DT_CPU_CLK_CTRL);
+ return -ENODEV;
+ }
+
+ priv->mdiv_clk = devm_clk_get(dev, BRCMSTB_CLK_MDIV_CH0);
+ priv->ndiv_clk = devm_clk_get(dev, BRCMSTB_CLK_NDIV_INT);
+ priv->sw_scb_clk = devm_clk_get(dev, BRCMSTB_CLK_SW_SCB);
+
+ if (IS_ERR(priv->mdiv_clk))
+ return PTR_ERR(priv->mdiv_clk);
+ if (IS_ERR(priv->ndiv_clk))
+ return PTR_ERR(priv->ndiv_clk);
+ if (IS_ERR(priv->sw_scb_clk))
+ return PTR_ERR(priv->sw_scb_clk);
+
+ priv->dev = dev;
+ platform_set_drvdata(pdev, priv);
+
+ return 0;
+}
+
+static int brcmstb_cpufreq_init(struct cpufreq_policy *policy)
+{
+ struct cpufreq_frequency_table *freq_table;
+ struct platform_device *pdev;
+ struct private_data *priv;
+ struct device *dev;
+ int ret;
+
+ pdev = cpufreq_get_driver_data();
+ priv = platform_get_drvdata(pdev);
+ dev = &pdev->dev;
+
+ policy->clk = priv->mdiv_clk;
+ policy->driver_data = priv;
+
+ freq_table = brcmstb_get_freq_table(policy);
+ if (IS_ERR(freq_table)) {
+ ret = PTR_ERR(freq_table);
+ dev_err(dev, "Couldn't determine frequency table (%d).\n", ret);
+ if (ret == -EINVAL)
+ dev_emerg(dev,
+ "Invalid number of memory controllers -- %d!\n",
+ count_memory_controllers());
+ return ret;
+ }
+
+ ret = cpufreq_generic_init(policy, freq_table, TRANSITION_LATENCY);
+ if (!ret)
+ dev_info(dev, "registered\n");
+
+ return ret;
+}
+
+/* Shows the number of memory controllers. */
+static ssize_t show_brcmstb_num_memc(struct cpufreq_policy *policy, char *buf)
+{
+ return sprintf(buf, "%u\n", count_memory_controllers());
+}
+
+/* Shows vco_freq, cpu_freq, and scb_freq in kHz. */
+static ssize_t show_brcmstb_freqs(struct cpufreq_policy *policy, char *buf)
+{
+ unsigned int vco_freq, cpu_freq, scb_freq;
+
+ get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
+
+ return sprintf(buf, "%u %u %u\n", vco_freq, cpu_freq, scb_freq);
+}
+
+/* Shows the lowest frequency (in kHz) that can be used without "safe mode". */
+static ssize_t show_brcmstb_safe_freq(struct cpufreq_policy *policy, char *buf)
+{
+ struct cpufreq_frequency_table *entry;
+ unsigned int safe_freq = 0;
+
+ cpufreq_for_each_valid_entry(entry, policy->freq_table) {
+ if (!(entry->driver_data & BRCMSTB_TBL_SAFE_MODE))
+ safe_freq = entry->frequency;
+ }
+
+ return sprintf(buf, "%u\n", safe_freq);
+}
+
+cpufreq_freq_attr_ro(brcmstb_num_memc);
+cpufreq_freq_attr_ro(brcmstb_freqs);
+cpufreq_freq_attr_ro(brcmstb_safe_freq);
+
+static struct freq_attr *brcmstb_cpufreq_attr[] = {
+ &cpufreq_freq_attr_scaling_available_freqs,
+ &brcmstb_num_memc,
+ &brcmstb_freqs,
+ &brcmstb_safe_freq,
+ NULL
+};
+
+static struct cpufreq_driver brcmstb_driver = {
+ .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK,
+ .verify = cpufreq_generic_frequency_table_verify,
+ .target_index = brcmstb_target_index,
+ .get = cpufreq_generic_get,
+ .init = brcmstb_cpufreq_init,
+ .attr = brcmstb_cpufreq_attr,
+ .name = BRCMSTB_CPUFREQ_PREFIX,
+};
+
+static int brcmstb_cpufreq_probe(struct platform_device *pdev)
+{
+ int ret;
+
+ ret = brcmstb_prepare_init(pdev);
+ if (ret)
+ return ret;
+
+ brcmstb_driver.driver_data = pdev;
+
+ return cpufreq_register_driver(&brcmstb_driver);
+}
+
+static int brcmstb_cpufreq_remove(struct platform_device *pdev)
+{
+ int ret;
+
+ ret = cpufreq_unregister_driver(&brcmstb_driver);
+ if (ret)
+ return ret;
+
+ platform_set_drvdata(pdev, NULL);
+
+ return 0;
+}
+
+static const struct of_device_id brcmstb_cpufreq_match[] = {
+ { .compatible = BRCMSTB_DT_CPU_CLK_CTRL },
+ { }
+};
+MODULE_DEVICE_TABLE(of, brcmstb_cpufreq_match);
+
+static struct platform_driver brcmstb_cpufreq_platdrv = {
+ .driver = {
+ .name = BRCMSTB_CPUFREQ_NAME,
+ .of_match_table = brcmstb_cpufreq_match,
+ },
+ .probe = brcmstb_cpufreq_probe,
+ .remove = brcmstb_cpufreq_remove,
+};
+module_platform_driver(brcmstb_cpufreq_platdrv);
+
+MODULE_AUTHOR("Markus Mayer <mmayer@broadcom.com>");
+MODULE_DESCRIPTION("CPUfreq driver for Broadcom STB SoCs");
+MODULE_LICENSE("GPL");
--
2.7.4
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