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>

arch/mips/include/asm/clock.h

@@ -0,0 +1,64 @@
+#ifndef __ASM_MIPS_CLOCK_H
+#define __ASM_MIPS_CLOCK_H
+
+#include <linux/kref.h>
+#include <linux/list.h>
+#include <linux/seq_file.h>
+#include <linux/clk.h>
+
+extern void (*cpu_wait) (void);
+
+struct clk;
+
+struct clk_ops {
+	void (*init) (struct clk *clk);
+	void (*enable) (struct clk *clk);
+	void (*disable) (struct clk *clk);
+	void (*recalc) (struct clk *clk);
+	int (*set_rate) (struct clk *clk, unsigned long rate, int algo_id);
+	long (*round_rate) (struct clk *clk, unsigned long rate);
+};
+
+struct clk {
+	struct list_head node;
+	const char *name;
+	int id;
+	struct module *owner;
+
+	struct clk *parent;
+	struct clk_ops *ops;
+
+	struct kref kref;
+
+	unsigned long rate;
+	unsigned long flags;
+};
+
+#define CLK_ALWAYS_ENABLED	(1 << 0)
+#define CLK_RATE_PROPAGATES	(1 << 1)
+
+/* Should be defined by processor-specific code */
+void arch_init_clk_ops(struct clk_ops **, int type);
+
+int clk_init(void);
+
+int __clk_enable(struct clk *);
+void __clk_disable(struct clk *);
+
+void clk_recalc_rate(struct clk *);
+
+int clk_register(struct clk *);
+void clk_unregister(struct clk *);
+
+/* the exported API, in addition to clk_set_rate */
+/**
+ * clk_set_rate_ex - set the clock rate for a clock source, with additional parameter
+ * @clk: clock source
+ * @rate: desired clock rate in Hz
+ * @algo_id: algorithm id to be passed down to ops->set_rate
+ *
+ * Returns success (0) or negative errno.
+ */
+int clk_set_rate_ex(struct clk *clk, unsigned long rate, int algo_id);
+
+#endif				/* __ASM_MIPS_CLOCK_H */

arch/mips/include/asm/cpu.h

@@ -154,6 +154,8 @@
 #define PRID_REV_VR4181A	0x0070	/* Same as VR4122 */
 #define PRID_REV_VR4130		0x0080
 #define PRID_REV_34K_V1_0_2	0x0022
+#define PRID_REV_LOONGSON2E	0x0002
+#define PRID_REV_LOONGSON2F	0x0003
 
 /*
  * Older processors used to encode processor version and revision in two

arch/mips/include/asm/mach-loongson/loongson.h

@@ -226,8 +226,12 @@ extern void mach_irq_dispatch(unsigned int pending);
 #define LOONGSON_PCIMAP_WIN(WIN, ADDR)	\
 	((((ADDR)>>26) & LOONGSON_PCIMAP_PCIMAP_LO0) << ((WIN)*6))
 
-/* Chip Config */
 #ifdef CONFIG_CPU_SUPPORTS_CPUFREQ
+#include <linux/cpufreq.h>
+extern void loongson2_cpu_wait(void);
+extern struct cpufreq_frequency_table loongson2_clockmod_table[];
+
+/* Chip Config */
 #define LOONGSON_CHIPCFG0		LOONGSON_REG(LOONGSON_REGBASE + 0x80)
 #endif
 

arch/mips/kernel/Makefile

@@ -93,4 +93,6 @@ CFLAGS_cpu-bugs64.o	= $(shell if $(CC) $(KBUILD_CFLAGS) -Wa,-mdaddi -c -o /dev/n
 
 obj-$(CONFIG_HAVE_STD_PC_SERIAL_PORT)	+= 8250-platform.o
 
+obj-$(CONFIG_MIPS_CPUFREQ)	+= cpufreq/
+
 EXTRA_CFLAGS += -Werror

arch/mips/kernel/cpu-probe.c

@@ -16,6 +16,7 @@
 #include <linux/ptrace.h>
 #include <linux/smp.h>
 #include <linux/stddef.h>
+#include <linux/module.h>
 
 #include <asm/bugs.h>
 #include <asm/cpu.h>
@@ -32,6 +33,7 @@
  * the CPU very much.
  */
 void (*cpu_wait)(void);
+EXPORT_SYMBOL(cpu_wait);
 
 static void r3081_wait(void)
 {

arch/mips/kernel/cpufreq/Kconfig

@@ -20,6 +20,20 @@ if CPU_FREQ
 
 comment "CPUFreq processor drivers"
 
+config LOONGSON2_CPUFREQ
+	tristate "Loongson2 CPUFreq Driver"
+	select CPU_FREQ_TABLE
+	depends on MIPS_CPUFREQ
+	help
+	  This option adds a CPUFreq driver for loongson processors which
+	  support software configurable cpu frequency.
+
+	  Loongson2F and it's successors support this feature.
+
+	  For details, take a look at <file:Documentation/cpu-freq/>.
+
+	  If in doubt, say N.
+
 endif	# CPU_FREQ
 
 endmenu

arch/mips/kernel/cpufreq/Makefile

@@ -0,0 +1,5 @@
+#
+# Makefile for the Linux/MIPS cpufreq.
+#
+
+obj-$(CONFIG_LOONGSON2_CPUFREQ) += loongson2_cpufreq.o loongson2_clock.o

arch/mips/kernel/cpufreq/loongson2_clock.c

@@ -0,0 +1,166 @@
+/*
+ * 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/platform_device.h>
+
+#include <asm/clock.h>
+
+#include <loongson.h>
+
+static LIST_HEAD(clock_list);
+static DEFINE_SPINLOCK(clock_lock);
+static DEFINE_MUTEX(clock_list_sem);
+
+/* Minimum CLK support */
+enum {
+	DC_ZERO, DC_25PT = 2, DC_37PT, DC_50PT, DC_62PT, DC_75PT,
+	DC_87PT, DC_DISABLE, DC_RESV
+};
+
+struct cpufreq_frequency_table loongson2_clockmod_table[] = {
+	{DC_RESV, CPUFREQ_ENTRY_INVALID},
+	{DC_ZERO, CPUFREQ_ENTRY_INVALID},
+	{DC_25PT, 0},
+	{DC_37PT, 0},
+	{DC_50PT, 0},
+	{DC_62PT, 0},
+	{DC_75PT, 0},
+	{DC_87PT, 0},
+	{DC_DISABLE, 0},
+	{DC_RESV, CPUFREQ_TABLE_END},
+};
+EXPORT_SYMBOL_GPL(loongson2_clockmod_table);
+
+static struct clk cpu_clk = {
+	.name = "cpu_clk",
+	.flags = CLK_ALWAYS_ENABLED | CLK_RATE_PROPAGATES,
+	.rate = 800000000,
+};
+
+struct clk *clk_get(struct device *dev, const char *id)
+{
+	return &cpu_clk;
+}
+EXPORT_SYMBOL(clk_get);
+
+static void propagate_rate(struct clk *clk)
+{
+	struct clk *clkp;
+
+	list_for_each_entry(clkp, &clock_list, node) {
+		if (likely(clkp->parent != clk))
+			continue;
+		if (likely(clkp->ops && clkp->ops->recalc))
+			clkp->ops->recalc(clkp);
+		if (unlikely(clkp->flags & CLK_RATE_PROPAGATES))
+			propagate_rate(clkp);
+	}
+}
+
+int clk_enable(struct clk *clk)
+{
+	return 0;
+}
+EXPORT_SYMBOL(clk_enable);
+
+void clk_disable(struct clk *clk)
+{
+}
+EXPORT_SYMBOL(clk_disable);
+
+unsigned long clk_get_rate(struct clk *clk)
+{
+	return (unsigned long)clk->rate;
+}
+EXPORT_SYMBOL(clk_get_rate);
+
+void clk_put(struct clk *clk)
+{
+}
+EXPORT_SYMBOL(clk_put);
+
+int clk_set_rate(struct clk *clk, unsigned long rate)
+{
+	return clk_set_rate_ex(clk, rate, 0);
+}
+EXPORT_SYMBOL_GPL(clk_set_rate);
+
+int clk_set_rate_ex(struct clk *clk, unsigned long rate, int algo_id)
+{
+	int ret = 0;
+	int regval;
+	int i;
+
+	if (likely(clk->ops && clk->ops->set_rate)) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&clock_lock, flags);
+		ret = clk->ops->set_rate(clk, rate, algo_id);
+		spin_unlock_irqrestore(&clock_lock, flags);
+	}
+
+	if (unlikely(clk->flags & CLK_RATE_PROPAGATES))
+		propagate_rate(clk);
+
+	for (i = 0; loongson2_clockmod_table[i].frequency != CPUFREQ_TABLE_END;
+	     i++) {
+		if (loongson2_clockmod_table[i].frequency ==
+		    CPUFREQ_ENTRY_INVALID)
+			continue;
+		if (rate == loongson2_clockmod_table[i].frequency)
+			break;
+	}
+	if (rate != loongson2_clockmod_table[i].frequency)
+		return -ENOTSUPP;
+
+	clk->rate = rate;
+
+	regval = LOONGSON_CHIPCFG0;
+	regval = (regval & ~0x7) | (loongson2_clockmod_table[i].index - 1);
+	LOONGSON_CHIPCFG0 = regval;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(clk_set_rate_ex);
+
+long clk_round_rate(struct clk *clk, unsigned long rate)
+{
+	if (likely(clk->ops && clk->ops->round_rate)) {
+		unsigned long flags, rounded;
+
+		spin_lock_irqsave(&clock_lock, flags);
+		rounded = clk->ops->round_rate(clk, rate);
+		spin_unlock_irqrestore(&clock_lock, flags);
+
+		return rounded;
+	}
+
+	return rate;
+}
+EXPORT_SYMBOL_GPL(clk_round_rate);
+
+/*
+ * This is the simple version of Loongson-2 wait, Maybe we need do this in
+ * interrupt disabled content
+ */
+
+DEFINE_SPINLOCK(loongson2_wait_lock);
+void loongson2_cpu_wait(void)
+{
+	u32 cpu_freq;
+	unsigned long flags;
+
+	spin_lock_irqsave(&loongson2_wait_lock, flags);
+	cpu_freq = LOONGSON_CHIPCFG0;
+	LOONGSON_CHIPCFG0 &= ~0x7;	/* Put CPU into wait mode */
+	LOONGSON_CHIPCFG0 = cpu_freq;	/* Restore CPU state */
+	spin_unlock_irqrestore(&loongson2_wait_lock, flags);
+}
+EXPORT_SYMBOL_GPL(loongson2_cpu_wait);