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>

3 files changed, 234 insertions, 0 deletions

diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index 73df7dbc250a..4de4dfae4ccc 100644
--- a/drivers/cpufreq/Kconfig
+++ b/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"
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 40c53dc1937e..215e447abec6 100644
--- a/drivers/cpufreq/Makefile
+++ b/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
diff --git a/drivers/cpufreq/ls1x-cpufreq.c b/drivers/cpufreq/ls1x-cpufreq.c
new file mode 100644
index 000000000000..25fbd6a1374f
--- /dev/null
+++ b/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");