davinci: add CPU idle driver

The patch adds support for DaVinci cpu idle driver.

Two idle states are defined:
1. Wait for interrupt
2. Wait for interrupt and DDR self-refresh (or power down)

Some DaVinci SoCs support putting DDR in self-refresh (eg Dm644x, DM6467)
while others support putting DDR in self-refresh and power down (eg DM35x,
DA8xx).

Putting DDR (or mDDR) in power down saves more power than self-refresh.

The patch has been tested on DA850/OMAP-L138 EVM.
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>

arch/arm/mach-davinci/Makefile

@@ -32,3 +32,4 @@ obj-$(CONFIG_MACH_DAVINCI_DA850_EVM)	+= board-da850-evm.o
 
 # Power Management
 obj-$(CONFIG_CPU_FREQ)			+= cpufreq.o
+obj-$(CONFIG_CPU_IDLE)			+= cpuidle.o

arch/arm/mach-davinci/cpuidle.c

+/*
+ * CPU idle for DaVinci SoCs
+ *
+ * Copyright (C) 2009 Texas Instruments Incorporated. http://www.ti.com/
+ *
+ * Derived from Marvell Kirkwood CPU idle code
+ * (arch/arm/mach-kirkwood/cpuidle.c)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#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/cpuidle.h>
+
+#define DAVINCI_CPUIDLE_MAX_STATES	2
+
+struct davinci_ops {
+	void (*enter) (u32 flags);
+	void (*exit) (u32 flags);
+	u32 flags;
+};
+
+/* fields in davinci_ops.flags */
+#define DAVINCI_CPUIDLE_FLAGS_DDR2_PWDN	BIT(0)
+
+static struct cpuidle_driver davinci_idle_driver = {
+	.name	= "cpuidle-davinci",
+	.owner	= THIS_MODULE,
+};
+
+static DEFINE_PER_CPU(struct cpuidle_device, davinci_cpuidle_device);
+static void __iomem *ddr2_reg_base;
+
+#define DDR2_SDRCR_OFFSET	0xc
+#define DDR2_SRPD_BIT		BIT(23)
+#define DDR2_LPMODEN_BIT	BIT(31)
+
+static void davinci_save_ddr_power(int enter, bool pdown)
+{
+	u32 val;
+
+	val = __raw_readl(ddr2_reg_base + DDR2_SDRCR_OFFSET);
+
+	if (enter) {
+		if (pdown)
+			val |= DDR2_SRPD_BIT;
+		else
+			val &= ~DDR2_SRPD_BIT;
+		val |= DDR2_LPMODEN_BIT;
+	} else {
+		val &= ~(DDR2_SRPD_BIT | DDR2_LPMODEN_BIT);
+	}
+
+	__raw_writel(val, ddr2_reg_base + DDR2_SDRCR_OFFSET);
+}
+
+static void davinci_c2state_enter(u32 flags)
+{
+	davinci_save_ddr_power(1, !!(flags & DAVINCI_CPUIDLE_FLAGS_DDR2_PWDN));
+}
+
+static void davinci_c2state_exit(u32 flags)
+{
+	davinci_save_ddr_power(0, !!(flags & DAVINCI_CPUIDLE_FLAGS_DDR2_PWDN));
+}
+
+static struct davinci_ops davinci_states[DAVINCI_CPUIDLE_MAX_STATES] = {
+	[1] = {
+		.enter	= davinci_c2state_enter,
+		.exit	= davinci_c2state_exit,
+	},
+};
+
+/* Actual code that puts the SoC in different idle states */
+static int davinci_enter_idle(struct cpuidle_device *dev,
+						struct cpuidle_state *state)
+{
+	struct davinci_ops *ops = cpuidle_get_statedata(state);
+	struct timeval before, after;
+	int idle_time;
+
+	local_irq_disable();
+	do_gettimeofday(&before);
+
+	if (ops && ops->enter)
+		ops->enter(ops->flags);
+	/* Wait for interrupt state */
+	cpu_do_idle();
+	if (ops && ops->exit)
+		ops->exit(ops->flags);
+
+	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;
+}
+
+static int __init davinci_cpuidle_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct cpuidle_device *device;
+	struct davinci_cpuidle_config *pdata = pdev->dev.platform_data;
+	struct resource *ddr2_regs;
+	resource_size_t len;
+
+	device = &per_cpu(davinci_cpuidle_device, smp_processor_id());
+
+	if (!pdata) {
+		dev_err(&pdev->dev, "cannot get platform data\n");
+		return -ENOENT;
+	}
+
+	ddr2_regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!ddr2_regs) {
+		dev_err(&pdev->dev, "cannot get DDR2 controller register base");
+		return -ENODEV;
+	}
+
+	len = resource_size(ddr2_regs);
+
+	ddr2_regs = request_mem_region(ddr2_regs->start, len, ddr2_regs->name);
+	if (!ddr2_regs)
+		return -EBUSY;
+
+	ddr2_reg_base = ioremap(ddr2_regs->start, len);
+	if (!ddr2_reg_base) {
+		ret = -ENOMEM;
+		goto ioremap_fail;
+	}
+
+	ret = cpuidle_register_driver(&davinci_idle_driver);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register driver\n");
+		goto driver_register_fail;
+	}
+
+	/* Wait for interrupt state */
+	device->states[0].enter = davinci_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 = davinci_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 (pdata->ddr2_pdown)
+		davinci_states[1].flags |= DAVINCI_CPUIDLE_FLAGS_DDR2_PWDN;
+	cpuidle_set_statedata(&device->states[1], &davinci_states[1]);
+
+	device->state_count = DAVINCI_CPUIDLE_MAX_STATES;
+
+	ret = cpuidle_register_device(device);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register device\n");
+		goto device_register_fail;
+	}
+
+	return 0;
+
+device_register_fail:
+	cpuidle_unregister_driver(&davinci_idle_driver);
+driver_register_fail:
+	iounmap(ddr2_reg_base);
+ioremap_fail:
+	release_mem_region(ddr2_regs->start, len);
+	return ret;
+}
+
+static struct platform_driver davinci_cpuidle_driver = {
+	.driver = {
+		.name	= "cpuidle-davinci",
+		.owner	= THIS_MODULE,
+	},
+};
+
+static int __init davinci_cpuidle_init(void)
+{
+	return platform_driver_probe(&davinci_cpuidle_driver,
+						davinci_cpuidle_probe);
+}
+device_initcall(davinci_cpuidle_init);
+

arch/arm/mach-davinci/include/mach/cpuidle.h

+/*
+ * TI DaVinci cpuidle platform support
+ *
+ * 2009 (C) Texas Instruments, Inc. http://www.ti.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.
+ */
+#ifndef _MACH_DAVINCI_CPUIDLE_H
+#define _MACH_DAVINCI_CPUIDLE_H
+
+struct davinci_cpuidle_config {
+	u32 ddr2_pdown;
+};
+
+#endif