MIPS: Loongson 2F: Add CPU frequency scaling support

Loongson 2F supports CPU clock scaling. When put it into wait mode by
setting the frequency as ZERO it will stay in this mode until an external
interrupt wakes the CPU again.

To enable clock scaling support, an external timer of a known stable rate
is required.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: cpufreq@vger.kernel.org,
Cc: Dave Jones <davej@redhat.com>,
Cc: Dominik Brodowski <linux@dominikbrodowski.net>,
Cc: yanh@lemote.com
Cc: huhb@lemote.com,
Patchwork: http://patchwork.linux-mips.org/patch/660/
Patchwork: http://patchwork.linux-mips.org/patch/751/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 227 insertions, 0 deletions

diff --git a/arch/mips/kernel/cpufreq/loongson2_cpufreq.c b/arch/mips/kernel/cpufreq/loongson2_cpufreq.c
new file mode 100644
index 000000000000..2f6a0b147ab8
--- /dev/null
+++ b/arch/mips/kernel/cpufreq/loongson2_cpufreq.c
@@ -0,0 +1,227 @@
+/*
+ * Cpufreq driver for the loongson-2 processors
+ *
+ * The 2E revision of loongson processor not support this feature.
+ *
+ * Copyright (C) 2006 - 2008 Lemote Inc. & Insititute of Computing Technology
+ * Author: Yanhua, yanh@lemote.com
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#include <linux/cpufreq.h>
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/sched.h>        /* set_cpus_allowed() */
+#include <linux/delay.h>
+#include <linux/platform_device.h>
+
+#include <asm/clock.h>
+
+#include <loongson.h>
+
+static uint nowait;
+
+static struct clk *cpuclk;
+
+static void (*saved_cpu_wait) (void);
+
+static int loongson2_cpu_freq_notifier(struct notifier_block *nb,
+                                        unsigned long val, void *data);
+
+static struct notifier_block loongson2_cpufreq_notifier_block = {
+        .notifier_call = loongson2_cpu_freq_notifier
+};
+
+static int loongson2_cpu_freq_notifier(struct notifier_block *nb,
+                                        unsigned long val, void *data)
+{
+        if (val == CPUFREQ_POSTCHANGE)
+                current_cpu_data.udelay_val = loops_per_jiffy;
+
+        return 0;
+}
+
+static unsigned int loongson2_cpufreq_get(unsigned int cpu)
+{
+        return clk_get_rate(cpuclk);
+}
+
+/*
+ * Here we notify other drivers of the proposed change and the final change.
+ */
+static int loongson2_cpufreq_target(struct cpufreq_policy *policy,
+                                     unsigned int target_freq,
+                                     unsigned int relation)
+{
+        unsigned int cpu = policy->cpu;
+        unsigned int newstate = 0;
+        cpumask_t cpus_allowed;
+        struct cpufreq_freqs freqs;
+        unsigned int freq;
+
+        if (!cpu_online(cpu))
+                return -ENODEV;
+
+        cpus_allowed = current->cpus_allowed;
+        set_cpus_allowed(current, cpumask_of_cpu(cpu));
+
+        if (cpufreq_frequency_table_target
+            (policy, &loongson2_clockmod_table[0], target_freq, relation,
+             &newstate))
+                return -EINVAL;
+
+        freq =
+            ((cpu_clock_freq / 1000) *
+             loongson2_clockmod_table[newstate].index) / 8;
+        if (freq < policy->min || freq > policy->max)
+                return -EINVAL;
+
+        pr_debug("cpufreq: requested frequency %u Hz\n", target_freq * 1000);
+
+        freqs.cpu = cpu;
+        freqs.old = loongson2_cpufreq_get(cpu);
+        freqs.new = freq;
+        freqs.flags = 0;
+
+        if (freqs.new == freqs.old)
+                return 0;
+
+        /* notifiers */
+        cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+
+        set_cpus_allowed(current, cpus_allowed);
+
+        /* setting the cpu frequency */
+        clk_set_rate(cpuclk, freq);
+
+        /* notifiers */
+        cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+
+        pr_debug("cpufreq: set frequency %u kHz\n", freq);
+
+        return 0;
+}
+
+static int loongson2_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+        int i;
+
+        if (!cpu_online(policy->cpu))
+                return -ENODEV;
+
+        cpuclk = clk_get(NULL, "cpu_clk");
+        if (IS_ERR(cpuclk)) {
+                printk(KERN_ERR "cpufreq: couldn't get CPU clk\n");
+                return PTR_ERR(cpuclk);
+        }
+
+        cpuclk->rate = cpu_clock_freq / 1000;
+        if (!cpuclk->rate)
+                return -EINVAL;
+
+        /* clock table init */
+        for (i = 2;
+             (loongson2_clockmod_table[i].frequency != CPUFREQ_TABLE_END);
+             i++)
+                loongson2_clockmod_table[i].frequency = (cpuclk->rate * i) / 8;
+
+        policy->cur = loongson2_cpufreq_get(policy->cpu);
+
+        cpufreq_frequency_table_get_attr(&loongson2_clockmod_table[0],
+                                         policy->cpu);
+
+        return cpufreq_frequency_table_cpuinfo(policy,
+                                            &loongson2_clockmod_table[0]);
+}
+
+static int loongson2_cpufreq_verify(struct cpufreq_policy *policy)
+{
+        return cpufreq_frequency_table_verify(policy,
+                                              &loongson2_clockmod_table[0]);
+}
+
+static int loongson2_cpufreq_exit(struct cpufreq_policy *policy)
+{
+        clk_put(cpuclk);
+        return 0;
+}
+
+static struct freq_attr *loongson2_table_attr[] = {
+        &cpufreq_freq_attr_scaling_available_freqs,
+        NULL,
+};
+
+static struct cpufreq_driver loongson2_cpufreq_driver = {
+        .owner = THIS_MODULE,
+        .name = "loongson2",
+        .init = loongson2_cpufreq_cpu_init,
+        .verify = loongson2_cpufreq_verify,
+        .target = loongson2_cpufreq_target,
+        .get = loongson2_cpufreq_get,
+        .exit = loongson2_cpufreq_exit,
+        .attr = loongson2_table_attr,
+};
+
+static struct platform_device_id platform_device_ids[] = {
+        {
+                .name = "loongson2_cpufreq",
+        },
+        {}
+};
+
+MODULE_DEVICE_TABLE(platform, platform_device_ids);
+
+static struct platform_driver platform_driver = {
+        .driver = {
+                .name = "loongson2_cpufreq",
+                .owner = THIS_MODULE,
+        },
+        .id_table = platform_device_ids,
+};
+
+static int __init cpufreq_init(void)
+{
+        int ret;
+
+        /* Register platform stuff */
+        ret = platform_driver_register(&platform_driver);
+        if (ret)
+                return ret;
+
+        pr_info("cpufreq: Loongson-2F CPU frequency driver.\n");
+
+        cpufreq_register_notifier(&loongson2_cpufreq_notifier_block,
+                                  CPUFREQ_TRANSITION_NOTIFIER);
+
+        ret = cpufreq_register_driver(&loongson2_cpufreq_driver);
+
+        if (!ret && !nowait) {
+                saved_cpu_wait = cpu_wait;
+                cpu_wait = loongson2_cpu_wait;
+        }
+
+        return ret;
+}
+
+static void __exit cpufreq_exit(void)
+{
+        if (!nowait && saved_cpu_wait)
+                cpu_wait = saved_cpu_wait;
+        cpufreq_unregister_driver(&loongson2_cpufreq_driver);
+        cpufreq_unregister_notifier(&loongson2_cpufreq_notifier_block,
+                                    CPUFREQ_TRANSITION_NOTIFIER);
+
+        platform_driver_unregister(&platform_driver);
+}
+
+module_init(cpufreq_init);
+module_exit(cpufreq_exit);
+
+module_param(nowait, uint, 0644);
+MODULE_PARM_DESC(nowait, "Disable Loongson-2F specific wait");
+
+MODULE_AUTHOR("Yanhua <yanh@lemote.com>");
+MODULE_DESCRIPTION("cpufreq driver for Loongson2F");
+MODULE_LICENSE("GPL");