cpufreq: Loongson1: Add cpufreq driver for Loongson1B

This patch adds cpufreq driver for Loongson1B which
is capable of changing the CPU frequency dynamically.

Signed-off-by: Kelvin Cheung <keguang.zhang@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/Kconfig

@@ -249,6 +249,16 @@ config LOONGSON2_CPUFREQ
 
 	  If in doubt, say N.
 
+config LOONGSON1_CPUFREQ
+	tristate "Loongson1 CPUFreq Driver"
+	help
+	  This option adds a CPUFreq driver for loongson1 processors which
+	  support software configurable cpu frequency.
+
+	  For details, take a look at <file:Documentation/cpu-freq/>.
+
+	  If in doubt, say N.
+
 endmenu
 
 menu "PowerPC CPU frequency scaling drivers"

drivers/cpufreq/Makefile

@@ -98,6 +98,7 @@ obj-$(CONFIG_CRIS_MACH_ARTPEC3)		+= cris-artpec3-cpufreq.o
 obj-$(CONFIG_ETRAXFS)			+= cris-etraxfs-cpufreq.o
 obj-$(CONFIG_IA64_ACPI_CPUFREQ)		+= ia64-acpi-cpufreq.o
 obj-$(CONFIG_LOONGSON2_CPUFREQ)		+= loongson2_cpufreq.o
+obj-$(CONFIG_LOONGSON1_CPUFREQ)		+= ls1x-cpufreq.o
 obj-$(CONFIG_SH_CPU_FREQ)		+= sh-cpufreq.o
 obj-$(CONFIG_SPARC_US2E_CPUFREQ)	+= sparc-us2e-cpufreq.o
 obj-$(CONFIG_SPARC_US3_CPUFREQ)		+= sparc-us3-cpufreq.o

drivers/cpufreq/ls1x-cpufreq.c

@@ -0,0 +1,223 @@
+/*
+ * CPU Frequency Scaling for Loongson 1 SoC
+ *
+ * Copyright (C) 2014 Zhang, Keguang <keguang.zhang@gmail.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/cpu.h>
+#include <linux/cpufreq.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include <asm/mach-loongson1/cpufreq.h>
+#include <asm/mach-loongson1/loongson1.h>
+
+static struct {
+	struct device *dev;
+	struct clk *clk;	/* CPU clk */
+	struct clk *mux_clk;	/* MUX of CPU clk */
+	struct clk *pll_clk;	/* PLL clk */
+	struct clk *osc_clk;	/* OSC clk */
+	unsigned int max_freq;
+	unsigned int min_freq;
+} ls1x_cpufreq;
+
+static int ls1x_cpufreq_notifier(struct notifier_block *nb,
+				 unsigned long val, void *data)
+{
+	if (val == CPUFREQ_POSTCHANGE)
+		current_cpu_data.udelay_val = loops_per_jiffy;
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block ls1x_cpufreq_notifier_block = {
+	.notifier_call = ls1x_cpufreq_notifier
+};
+
+static int ls1x_cpufreq_target(struct cpufreq_policy *policy,
+			       unsigned int index)
+{
+	unsigned int old_freq, new_freq;
+
+	old_freq = policy->cur;
+	new_freq = policy->freq_table[index].frequency;
+
+	/*
+	 * The procedure of reconfiguring CPU clk is as below.
+	 *
+	 *  - Reparent CPU clk to OSC clk
+	 *  - Reset CPU clock (very important)
+	 *  - Reconfigure CPU DIV
+	 *  - Reparent CPU clk back to CPU DIV clk
+	 */
+
+	dev_dbg(ls1x_cpufreq.dev, "%u KHz --> %u KHz\n", old_freq, new_freq);
+	clk_set_parent(policy->clk, ls1x_cpufreq.osc_clk);
+	__raw_writel(__raw_readl(LS1X_CLK_PLL_DIV) | RST_CPU_EN | RST_CPU,
+		     LS1X_CLK_PLL_DIV);
+	__raw_writel(__raw_readl(LS1X_CLK_PLL_DIV) & ~(RST_CPU_EN | RST_CPU),
+		     LS1X_CLK_PLL_DIV);
+	clk_set_rate(ls1x_cpufreq.mux_clk, new_freq * 1000);
+	clk_set_parent(policy->clk, ls1x_cpufreq.mux_clk);
+
+	return 0;
+}
+
+static int ls1x_cpufreq_init(struct cpufreq_policy *policy)
+{
+	struct cpufreq_frequency_table *freq_tbl;
+	unsigned int pll_freq, freq;
+	int steps, i, ret;
+
+	pll_freq = clk_get_rate(ls1x_cpufreq.pll_clk) / 1000;
+
+	steps = 1 << DIV_CPU_WIDTH;
+	freq_tbl = kzalloc(sizeof(*freq_tbl) * steps, GFP_KERNEL);
+	if (!freq_tbl) {
+		dev_err(ls1x_cpufreq.dev,
+			"failed to alloc cpufreq_frequency_table\n");
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	for (i = 0; i < (steps - 1); i++) {
+		freq = pll_freq / (i + 1);
+		if ((freq < ls1x_cpufreq.min_freq) ||
+		    (freq > ls1x_cpufreq.max_freq))
+			freq_tbl[i].frequency = CPUFREQ_ENTRY_INVALID;
+		else
+			freq_tbl[i].frequency = freq;
+		dev_dbg(ls1x_cpufreq.dev,
+			"cpufreq table: index %d: frequency %d\n", i,
+			freq_tbl[i].frequency);
+	}
+	freq_tbl[i].frequency = CPUFREQ_TABLE_END;
+
+	policy->clk = ls1x_cpufreq.clk;
+	ret = cpufreq_generic_init(policy, freq_tbl, 0);
+	if (ret)
+		kfree(freq_tbl);
+out:
+	return ret;
+}
+
+static int ls1x_cpufreq_exit(struct cpufreq_policy *policy)
+{
+	kfree(policy->freq_table);
+	return 0;
+}
+
+static struct cpufreq_driver ls1x_cpufreq_driver = {
+	.name		= "cpufreq-ls1x",
+	.flags		= CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK,
+	.verify		= cpufreq_generic_frequency_table_verify,
+	.target_index	= ls1x_cpufreq_target,
+	.get		= cpufreq_generic_get,
+	.init		= ls1x_cpufreq_init,
+	.exit		= ls1x_cpufreq_exit,
+	.attr		= cpufreq_generic_attr,
+};
+
+static int ls1x_cpufreq_remove(struct platform_device *pdev)
+{
+	cpufreq_unregister_notifier(&ls1x_cpufreq_notifier_block,
+				    CPUFREQ_TRANSITION_NOTIFIER);
+	cpufreq_unregister_driver(&ls1x_cpufreq_driver);
+
+	return 0;
+}
+
+static int ls1x_cpufreq_probe(struct platform_device *pdev)
+{
+	struct plat_ls1x_cpufreq *pdata = pdev->dev.platform_data;
+	struct clk *clk;
+	int ret;
+
+	if (!pdata || !pdata->clk_name || !pdata->osc_clk_name)
+		return -EINVAL;
+
+	ls1x_cpufreq.dev = &pdev->dev;
+
+	clk = devm_clk_get(&pdev->dev, pdata->clk_name);
+	if (IS_ERR(clk)) {
+		dev_err(ls1x_cpufreq.dev, "unable to get %s clock\n",
+			pdata->clk_name);
+		ret = PTR_ERR(clk);
+		goto out;
+	}
+	ls1x_cpufreq.clk = clk;
+
+	clk = clk_get_parent(clk);
+	if (IS_ERR(clk)) {
+		dev_err(ls1x_cpufreq.dev, "unable to get parent of %s clock\n",
+			__clk_get_name(ls1x_cpufreq.clk));
+		ret = PTR_ERR(clk);
+		goto out;
+	}
+	ls1x_cpufreq.mux_clk = clk;
+
+	clk = clk_get_parent(clk);
+	if (IS_ERR(clk)) {
+		dev_err(ls1x_cpufreq.dev, "unable to get parent of %s clock\n",
+			__clk_get_name(ls1x_cpufreq.mux_clk));
+		ret = PTR_ERR(clk);
+		goto out;
+	}
+	ls1x_cpufreq.pll_clk = clk;
+
+	clk = devm_clk_get(&pdev->dev, pdata->osc_clk_name);
+	if (IS_ERR(clk)) {
+		dev_err(ls1x_cpufreq.dev, "unable to get %s clock\n",
+			pdata->osc_clk_name);
+		ret = PTR_ERR(clk);
+		goto out;
+	}
+	ls1x_cpufreq.osc_clk = clk;
+
+	ls1x_cpufreq.max_freq = pdata->max_freq;
+	ls1x_cpufreq.min_freq = pdata->min_freq;
+
+	ret = cpufreq_register_driver(&ls1x_cpufreq_driver);
+	if (ret) {
+		dev_err(ls1x_cpufreq.dev,
+			"failed to register cpufreq driver: %d\n", ret);
+		goto out;
+	}
+
+	ret = cpufreq_register_notifier(&ls1x_cpufreq_notifier_block,
+					CPUFREQ_TRANSITION_NOTIFIER);
+
+	if (!ret)
+		goto out;
+
+	dev_err(ls1x_cpufreq.dev, "failed to register cpufreq notifier: %d\n",
+		ret);
+
+	cpufreq_unregister_driver(&ls1x_cpufreq_driver);
+out:
+	return ret;
+}
+
+static struct platform_driver ls1x_cpufreq_platdrv = {
+	.driver = {
+		.name	= "ls1x-cpufreq",
+		.owner	= THIS_MODULE,
+	},
+	.probe		= ls1x_cpufreq_probe,
+	.remove		= ls1x_cpufreq_remove,
+};
+
+module_platform_driver(ls1x_cpufreq_platdrv);
+
+MODULE_AUTHOR("Kelvin Cheung <keguang.zhang@gmail.com>");
+MODULE_DESCRIPTION("Loongson 1 CPUFreq driver");
+MODULE_LICENSE("GPL");