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>

1 files changed, 197 insertions, 0 deletions

diff --git a/arch/arm/mach-davinci/cpuidle.c b/arch/arm/mach-davinci/cpuidle.c
new file mode 100644
index 000000000000..97a90f36fc92
--- /dev/null
+++ b/arch/arm/mach-davinci/cpuidle.c
@@ -0,0 +1,197 @@
+/*
+ * 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);
+