[ARM] Kirkwood: CPU idle driver

The patch adds support for Kirkwood cpu idle.
Two idle states are defined:
1. Wait-for-interrupt (replacing default kirkwood wfi)
2. Wait-for-interrupt and DDR self refresh

Signed-off-by: Rabeeh Khoury <rabeeh@marvell.com>
Signed-off-by: Nicolas Pitre <nico@marvell.com>

arch/arm/configs/kirkwood_defconfig

@@ -270,7 +270,9 @@ CONFIG_CMDLINE=""
 #
 # CPU Power Management
 #
-# CONFIG_CPU_IDLE is not set
+CONFIG_CPU_IDLE=y
+CONFIG_CPU_IDLE_GOV_LADDER=y
+CONFIG_CPU_IDLE_GOV_MENU=y
 
 #
 # Floating point emulation

arch/arm/mach-kirkwood/Makefile

@@ -5,3 +5,5 @@ obj-$(CONFIG_MACH_RD88F6192_NAS)	+= rd88f6192-nas-setup.o
 obj-$(CONFIG_MACH_RD88F6281)		+= rd88f6281-setup.o
 obj-$(CONFIG_MACH_SHEEVAPLUG)		+= sheevaplug-setup.o
 obj-$(CONFIG_MACH_TS219)		+= ts219-setup.o
+
+obj-$(CONFIG_CPU_IDLE)			+= cpuidle.o

arch/arm/mach-kirkwood/cpuidle.c

@@ -0,0 +1,96 @@
+/*
+ * arch/arm/mach-kirkwood/cpuidle.c
+ *
+ * CPU idle Marvell Kirkwood SoCs
+ *
+ * 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.
+ *
+ * The cpu idle uses wait-for-interrupt and DDR self refresh in order
+ * to implement two idle states -
+ * #1 wait-for-interrupt
+ * #2 wait-for-interrupt and DDR self refresh
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/cpuidle.h>
+#include <linux/io.h>
+#include <asm/proc-fns.h>
+#include <mach/kirkwood.h>
+
+#define KIRKWOOD_MAX_STATES	2
+
+static struct cpuidle_driver kirkwood_idle_driver = {
+	.name =         "kirkwood_idle",
+	.owner =        THIS_MODULE,
+};
+
+static DEFINE_PER_CPU(struct cpuidle_device, kirkwood_cpuidle_device);
+
+/* Actual code that puts the SoC in different idle states */
+static int kirkwood_enter_idle(struct cpuidle_device *dev,
+			       struct cpuidle_state *state)
+{
+	struct timeval before, after;
+	int idle_time;
+
+	local_irq_disable();
+	do_gettimeofday(&before);
+	if (state == &dev->states[0])
+		/* Wait for interrupt state */
+		cpu_do_idle();
+	else if (state == &dev->states[1]) {
+		/*
+		 * Following write will put DDR in self refresh.
+		 * Note that we have 256 cycles before DDR puts it
+		 * self in self-refresh, so the wait-for-interrupt
+		 * call afterwards won't get the DDR from self refresh
+		 * mode.
+		 */
+		writel(0x7, DDR_OPERATION_BASE);
+		cpu_do_idle();
+	}
+	do_gettimeofday(&after);
+	local_irq_enable();
+	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +
+			(after.tv_usec - before.tv_usec);
+	return idle_time;
+}
+
+/* Initialize CPU idle by registering the idle states */
+static int kirkwood_init_cpuidle(void)
+{
+	struct cpuidle_device *device;
+
+	cpuidle_register_driver(&kirkwood_idle_driver);
+
+	device = &per_cpu(kirkwood_cpuidle_device, smp_processor_id());
+	device->state_count = KIRKWOOD_MAX_STATES;
+
+	/* Wait for interrupt state */
+	device->states[0].enter = kirkwood_enter_idle;
+	device->states[0].exit_latency = 1;
+	device->states[0].target_residency = 10000;
+	device->states[0].flags = CPUIDLE_FLAG_TIME_VALID;
+	strcpy(device->states[0].name, "WFI");
+	strcpy(device->states[0].desc, "Wait for interrupt");
+
+	/* Wait for interrupt and DDR self refresh state */
+	device->states[1].enter = kirkwood_enter_idle;
+	device->states[1].exit_latency = 10;
+	device->states[1].target_residency = 10000;
+	device->states[1].flags = CPUIDLE_FLAG_TIME_VALID;
+	strcpy(device->states[1].name, "DDR SR");
+	strcpy(device->states[1].desc, "WFI and DDR Self Refresh");
+
+	if (cpuidle_register_device(device)) {
+		printk(KERN_ERR "kirkwood_init_cpuidle: Failed registering\n");
+		return -EIO;
+	}
+	return 0;
+}
+
+device_initcall(kirkwood_init_cpuidle);

arch/arm/mach-kirkwood/include/mach/kirkwood.h

@@ -48,6 +48,7 @@
  */
 #define DDR_VIRT_BASE		(KIRKWOOD_REGS_VIRT_BASE | 0x00000)
 #define  DDR_WINDOW_CPU_BASE	(DDR_VIRT_BASE | 0x1500)
+#define DDR_OPERATION_BASE	(DDR_VIRT_BASE | 0x1418)
 
 #define DEV_BUS_PHYS_BASE	(KIRKWOOD_REGS_PHYS_BASE | 0x10000)
 #define DEV_BUS_VIRT_BASE	(KIRKWOOD_REGS_VIRT_BASE | 0x10000)