Merge tag 'v3.18-rockchip-clk2' of git://git.kernel.org/pub/scm/linux/kernel/git/mmind/linux-rockchip into clk-next

Allow parent rate changes for i2s on rk3288
and rockchip as well as s3c24xx restart handlers.

14 files changed, 247 insertions, 46 deletions

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 81ef686a91ca..250b6f652afc 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -114,18 +114,13 @@ void soft_restart(unsigned long addr)
         BUG();
 }
 
-static void null_restart(enum reboot_mode reboot_mode, const char *cmd)
-{
-}
-
 /*
  * Function pointers to optional machine specific functions
  */
 void (*pm_power_off)(void);
 EXPORT_SYMBOL(pm_power_off);
 
-void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd) = null_restart;
-EXPORT_SYMBOL_GPL(arm_pm_restart);
+void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
 
 /*
  * This is our default idle handler.
@@ -230,7 +225,10 @@ void machine_restart(char *cmd)
         local_irq_disable();
         smp_send_stop();
 
-        arm_pm_restart(reboot_mode, cmd);
+        if (arm_pm_restart)
+                arm_pm_restart(reboot_mode, cmd);
+        else
+                do_kernel_restart(cmd);
 
         /* Give a grace period for failure to restart of 1s */
         mdelay(1000);
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 29d48690f2ac..e0ef8ba4fdb9 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -98,7 +98,6 @@ void (*pm_power_off)(void);
 EXPORT_SYMBOL_GPL(pm_power_off);
 
 void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
-EXPORT_SYMBOL_GPL(arm_pm_restart);
 
 /*
  * This is our default idle handler.
@@ -180,6 +179,8 @@ void machine_restart(char *cmd)
         /* Now call the architecture specific reboot code. */
         if (arm_pm_restart)
                 arm_pm_restart(reboot_mode, cmd);
+        else
+                do_kernel_restart(cmd);
 
         /*
          * Whoops - the architecture was unable to reboot.
diff --git a/drivers/clk/rockchip/clk-rk3188.c b/drivers/clk/rockchip/clk-rk3188.c
index ceabce595498..beed49c79126 100644
--- a/drivers/clk/rockchip/clk-rk3188.c
+++ b/drivers/clk/rockchip/clk-rk3188.c
@@ -735,6 +735,8 @@ static void __init rk3188_common_clk_init(struct device_node *np)
 
         rockchip_register_softrst(np, 9, reg_base + RK2928_SOFTRST_CON(0),
                                   ROCKCHIP_SOFTRST_HIWORD_MASK);
+
+        rockchip_register_restart_notifier(RK2928_GLB_SRST_FST);
 }
 
 static void __init rk3066a_clk_init(struct device_node *np)
diff --git a/drivers/clk/rockchip/clk-rk3288.c b/drivers/clk/rockchip/clk-rk3288.c
index d053529113f8..23278291da44 100644
--- a/drivers/clk/rockchip/clk-rk3288.c
+++ b/drivers/clk/rockchip/clk-rk3288.c
@@ -300,15 +300,15 @@ static struct rockchip_clk_branch rk3288_clk_branches[] __initdata = {
         COMPOSITE(0, "i2s_src", mux_pll_src_cpll_gpll_p, 0,
                         RK3288_CLKSEL_CON(4), 15, 1, MFLAGS, 0, 7, DFLAGS,
                         RK3288_CLKGATE_CON(4), 1, GFLAGS),
-        COMPOSITE_FRAC(0, "i2s_frac", "i2s_src", 0,
+        COMPOSITE_FRAC(0, "i2s_frac", "i2s_src", CLK_SET_RATE_PARENT,
                         RK3288_CLKSEL_CON(8), 0,
                         RK3288_CLKGATE_CON(4), 2, GFLAGS),
-        MUX(0, "i2s_pre", mux_i2s_pre_p, 0,
+        MUX(0, "i2s_pre", mux_i2s_pre_p, CLK_SET_RATE_PARENT,
                         RK3288_CLKSEL_CON(4), 8, 2, MFLAGS),
-        COMPOSITE_NODIV(0, "i2s0_clkout", mux_i2s_clkout_p, 0,
+        COMPOSITE_NODIV(0, "i2s0_clkout", mux_i2s_clkout_p, CLK_SET_RATE_PARENT,
                         RK3288_CLKSEL_CON(4), 12, 1, MFLAGS,
                         RK3288_CLKGATE_CON(4), 0, GFLAGS),
-        GATE(SCLK_I2S0, "sclk_i2s0", "i2s_pre", 0,
+        GATE(SCLK_I2S0, "sclk_i2s0", "i2s_pre", CLK_SET_RATE_PARENT,
                         RK3288_CLKGATE_CON(4), 3, GFLAGS),
 
         MUX(0, "spdif_src", mux_pll_src_cpll_gpll_p, 0,
@@ -808,5 +808,7 @@ static void __init rk3288_clk_init(struct device_node *np)
 
         rockchip_register_softrst(np, 12, reg_base + RK3288_SOFTRST_CON(0),
                                   ROCKCHIP_SOFTRST_HIWORD_MASK);
+
+        rockchip_register_restart_notifier(RK3288_GLB_SRST_FST);
 }
 CLK_OF_DECLARE(rk3288_cru, "rockchip,rk3288-cru", rk3288_clk_init);
diff --git a/drivers/clk/rockchip/clk.c b/drivers/clk/rockchip/clk.c
index fd3b5ef87e29..1e68bff481b8 100644
--- a/drivers/clk/rockchip/clk.c
+++ b/drivers/clk/rockchip/clk.c
@@ -25,6 +25,7 @@
 #include <linux/clk-provider.h>
 #include <linux/mfd/syscon.h>
 #include <linux/regmap.h>
+#include <linux/reboot.h>
 #include "clk.h"
 
 /**
@@ -330,3 +331,27 @@ void __init rockchip_clk_protect_critical(const char *clocks[], int nclocks)
                         clk_prepare_enable(clk);
         }
 }
+
+static unsigned int reg_restart;
+static int rockchip_restart_notify(struct notifier_block *this,
+                                   unsigned long mode, void *cmd)
+{
+        writel(0xfdb9, reg_base + reg_restart);
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block rockchip_restart_handler = {
+        .notifier_call = rockchip_restart_notify,
+        .priority = 128,
+};
+
+void __init rockchip_register_restart_notifier(unsigned int reg)
+{
+        int ret;
+
+        reg_restart = reg;
+        ret = register_restart_handler(&rockchip_restart_handler);
+        if (ret)
+                pr_err("%s: cannot register restart handler, %d\n",
+                       __func__, ret);
+}
diff --git a/drivers/clk/rockchip/clk.h b/drivers/clk/rockchip/clk.h
index f4791fbb3da9..ca009ab0a33a 100644
--- a/drivers/clk/rockchip/clk.h
+++ b/drivers/clk/rockchip/clk.h
@@ -367,6 +367,7 @@ void rockchip_clk_register_armclk(unsigned int lookup_id, const char *name,
                         const struct rockchip_cpuclk_rate_table *rates,
                         int nrates);
 void rockchip_clk_protect_critical(const char *clocks[], int nclocks);
+void rockchip_register_restart_notifier(unsigned int reg);
 
 #define ROCKCHIP_SOFTRST_HIWORD_MASK    BIT(0)
 
diff --git a/drivers/clk/samsung/clk-s3c2412.c b/drivers/clk/samsung/clk-s3c2412.c
index 34af09f6a155..2ceedaf8ce18 100644
--- a/drivers/clk/samsung/clk-s3c2412.c
+++ b/drivers/clk/samsung/clk-s3c2412.c
@@ -14,6 +14,7 @@
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/syscore_ops.h>
+#include <linux/reboot.h>
 
 #include <dt-bindings/clock/s3c2412.h>
 
@@ -26,6 +27,7 @@
 #define CLKCON          0x0c
 #define CLKDIVN         0x14
 #define CLKSRC          0x1c
+#define SWRST           0x30
 
 /* list of PLLs to be registered */
 enum s3c2412_plls {
@@ -204,6 +206,28 @@ struct samsung_clock_alias s3c2412_aliases[] __initdata = {
         ALIAS(MSYSCLK, NULL, "fclk"),
 };
 
+static int s3c2412_restart(struct notifier_block *this,
+                           unsigned long mode, void *cmd)
+{
+        /* errata "Watch-dog/Software Reset Problem" specifies that
+         * this reset must be done with the SYSCLK sourced from
+         * EXTCLK instead of FOUT to avoid a glitch in the reset
+         * mechanism.
+         *
+         * See the watchdog section of the S3C2412 manual for more
+         * information on this fix.
+         */
+
+        __raw_writel(0x00, reg_base + CLKSRC);
+        __raw_writel(0x533C2412, reg_base + SWRST);
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block s3c2412_restart_handler = {
+        .notifier_call = s3c2412_restart,
+        .priority = 129,
+};
+
 /*
  * fixed rate clocks generated outside the soc
  * Only necessary until the devicetree-move is complete
@@ -233,6 +257,7 @@ void __init s3c2412_common_clk_init(struct device_node *np, unsigned long xti_f,
                                     unsigned long ext_f, void __iomem *base)
 {
         struct samsung_clk_provider *ctx;
+        int ret;
         reg_base = base;
 
         if (np) {
@@ -267,6 +292,10 @@ void __init s3c2412_common_clk_init(struct device_node *np, unsigned long xti_f,
         s3c2412_clk_sleep_init();
 
         samsung_clk_of_add_provider(np, ctx);
+
+        ret = register_restart_handler(&s3c2412_restart_handler);
+        if (ret)
+                pr_warn("cannot register restart handler, %d\n", ret);
 }
 
 static void __init s3c2412_clk_init(struct device_node *np)
diff --git a/drivers/clk/samsung/clk-s3c2443.c b/drivers/clk/samsung/clk-s3c2443.c
index c92f853fca9f..0c3c182b902a 100644
--- a/drivers/clk/samsung/clk-s3c2443.c
+++ b/drivers/clk/samsung/clk-s3c2443.c
@@ -14,6 +14,7 @@
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/syscore_ops.h>
+#include <linux/reboot.h>
 
 #include <dt-bindings/clock/s3c2443.h>
 
@@ -33,6 +34,7 @@
 #define HCLKCON         0x30
 #define PCLKCON         0x34
 #define SCLKCON         0x38
+#define SWRST           0x44
 
 /* the soc types */
 enum supported_socs {
@@ -354,6 +356,18 @@ struct samsung_clock_alias s3c2450_aliases[] __initdata = {
         ALIAS(PCLK_I2C1, "s3c2410-i2c.1", "i2c"),
 };
 
+static int s3c2443_restart(struct notifier_block *this,
+                           unsigned long mode, void *cmd)
+{
+        __raw_writel(0x533c2443, reg_base + SWRST);
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block s3c2443_restart_handler = {
+        .notifier_call = s3c2443_restart,
+        .priority = 129,
+};
+
 /*
  * fixed rate clocks generated outside the soc
  * Only necessary until the devicetree-move is complete
@@ -378,6 +392,7 @@ void __init s3c2443_common_clk_init(struct device_node *np, unsigned long xti_f,
                                     void __iomem *base)
 {
         struct samsung_clk_provider *ctx;
+        int ret;
         reg_base = base;
 
         if (np) {
@@ -447,6 +462,10 @@ void __init s3c2443_common_clk_init(struct device_node *np, unsigned long xti_f,
         s3c2443_clk_sleep_init();
 
         samsung_clk_of_add_provider(np, ctx);
+
+        ret = register_restart_handler(&s3c2443_restart_handler);
+        if (ret)
+                pr_warn("cannot register restart handler, %d\n", ret);
 }
 
 static void __init s3c2416_clk_init(struct device_node *np)
diff --git a/drivers/power/reset/restart-poweroff.c b/drivers/power/reset/restart-poweroff.c
index 3e51f8d29bfe..edd707ee7281 100644
--- a/drivers/power/reset/restart-poweroff.c
+++ b/drivers/power/reset/restart-poweroff.c
@@ -20,7 +20,8 @@
 
 static void restart_poweroff_do_poweroff(void)
 {
-        arm_pm_restart(REBOOT_HARD, NULL);
+        reboot_mode = REBOOT_HARD;
+        machine_restart(NULL);
 }
 
 static int restart_poweroff_probe(struct platform_device *pdev)
diff --git a/drivers/watchdog/alim7101_wdt.c b/drivers/watchdog/alim7101_wdt.c
index 996b2f7d330e..665e0e7dfe1e 100644
--- a/drivers/watchdog/alim7101_wdt.c
+++ b/drivers/watchdog/alim7101_wdt.c
@@ -301,6 +301,28 @@ static struct miscdevice wdt_miscdev = {
         .fops   =       &wdt_fops,
 };
 
+static int wdt_restart_handle(struct notifier_block *this, unsigned long mode,
+                              void *cmd)
+{
+        /*
+         * Cobalt devices have no way of rebooting themselves other
+         * than getting the watchdog to pull reset, so we restart the
+         * watchdog on reboot with no heartbeat.
+         */
+        wdt_change(WDT_ENABLE);
+
+        /* loop until the watchdog fires */
+        while (true)
+                ;
+
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block wdt_restart_handler = {
+        .notifier_call = wdt_restart_handle,
+        .priority = 128,
+};
+
 /*
  *      Notifier for system down
  */
@@ -311,15 +333,6 @@ static int wdt_notify_sys(struct notifier_block *this,
         if (code == SYS_DOWN || code == SYS_HALT)
                 wdt_turnoff();
 
-        if (code == SYS_RESTART) {
-                /*
-                 * Cobalt devices have no way of rebooting themselves other
-                 * than getting the watchdog to pull reset, so we restart the
-                 * watchdog on reboot with no heartbeat
-                 */
-                wdt_change(WDT_ENABLE);
-                pr_info("Watchdog timer is now enabled with no heartbeat - should reboot in ~1 second\n");
-        }
         return NOTIFY_DONE;
 }
 
@@ -338,6 +351,7 @@ static void __exit alim7101_wdt_unload(void)
         /* Deregister */
         misc_deregister(&wdt_miscdev);
         unregister_reboot_notifier(&wdt_notifier);
+        unregister_restart_handler(&wdt_restart_handler);
         pci_dev_put(alim7101_pmu);
 }
 
@@ -390,11 +404,17 @@ static int __init alim7101_wdt_init(void)
                 goto err_out;
         }
 
+        rc = register_restart_handler(&wdt_restart_handler);
+        if (rc) {
+                pr_err("cannot register restart handler (err=%d)\n", rc);
+                goto err_out_reboot;
+        }
+
         rc = misc_register(&wdt_miscdev);
         if (rc) {
                 pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                        wdt_miscdev.minor, rc);
-                goto err_out_reboot;
+                goto err_out_restart;
         }
 
         if (nowayout)
@@ -404,6 +424,8 @@ static int __init alim7101_wdt_init(void)
                 timeout, nowayout);
         return 0;
 
+err_out_restart:
+        unregister_restart_handler(&wdt_restart_handler);
 err_out_reboot:
         unregister_reboot_notifier(&wdt_notifier);
 err_out:
diff --git a/drivers/watchdog/moxart_wdt.c b/drivers/watchdog/moxart_wdt.c
index 4aa3a8a876fe..a64405b82596 100644
--- a/drivers/watchdog/moxart_wdt.c
+++ b/drivers/watchdog/moxart_wdt.c
@@ -15,12 +15,12 @@
 #include <linux/module.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
+#include <linux/notifier.h>
 #include <linux/platform_device.h>
+#include <linux/reboot.h>
 #include <linux/watchdog.h>
 #include <linux/moduleparam.h>
 
-#include <asm/system_misc.h>
-
 #define REG_COUNT                       0x4
 #define REG_MODE                        0x8
 #define REG_ENABLE                      0xC
@@ -29,17 +29,22 @@ struct moxart_wdt_dev {
         struct watchdog_device dev;
         void __iomem *base;
         unsigned int clock_frequency;
+        struct notifier_block restart_handler;
 };
 
-static struct moxart_wdt_dev *moxart_restart_ctx;
-
 static int heartbeat;
 
-static void moxart_wdt_restart(enum reboot_mode reboot_mode, const char *cmd)
+static int moxart_restart_handle(struct notifier_block *this,
+                                 unsigned long mode, void *cmd)
 {
-        writel(1, moxart_restart_ctx->base + REG_COUNT);
-        writel(0x5ab9, moxart_restart_ctx->base + REG_MODE);
-        writel(0x03, moxart_restart_ctx->base + REG_ENABLE);
+        struct moxart_wdt_dev *moxart_wdt = container_of(this,
+                                                         struct moxart_wdt_dev,
+                                                         restart_handler);
+        writel(1, moxart_wdt->base + REG_COUNT);
+        writel(0x5ab9, moxart_wdt->base + REG_MODE);
+        writel(0x03, moxart_wdt->base + REG_ENABLE);
+
+        return NOTIFY_DONE;
 }
 
 static int moxart_wdt_stop(struct watchdog_device *wdt_dev)
@@ -136,8 +141,12 @@ static int moxart_wdt_probe(struct platform_device *pdev)
         if (err)
                 return err;
 
-        moxart_restart_ctx = moxart_wdt;
-        arm_pm_restart = moxart_wdt_restart;
+        moxart_wdt->restart_handler.notifier_call = moxart_restart_handle;
+        moxart_wdt->restart_handler.priority = 128;
+        err = register_restart_handler(&moxart_wdt->restart_handler);
+        if (err)
+                dev_err(dev, "cannot register restart notifier (err=%d)\n",
+                        err);
 
         dev_dbg(dev, "Watchdog enabled (heartbeat=%d sec, nowayout=%d)\n",
                 moxart_wdt->dev.timeout, nowayout);
@@ -149,9 +158,8 @@ static int moxart_wdt_remove(struct platform_device *pdev)
 {
         struct moxart_wdt_dev *moxart_wdt = platform_get_drvdata(pdev);
 
-        arm_pm_restart = NULL;
+        unregister_restart_handler(&moxart_wdt->restart_handler);
         moxart_wdt_stop(&moxart_wdt->dev);
-        watchdog_unregister_device(&moxart_wdt->dev);
 
         return 0;
 }
diff --git a/drivers/watchdog/sunxi_wdt.c b/drivers/watchdog/sunxi_wdt.c
index 60deb9d304c0..480bb557f353 100644
--- a/drivers/watchdog/sunxi_wdt.c
+++ b/drivers/watchdog/sunxi_wdt.c
@@ -21,14 +21,13 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
+#include <linux/notifier.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/reboot.h>
 #include <linux/types.h>
 #include <linux/watchdog.h>
 
-#include <asm/system_misc.h>
-
 #define WDT_MAX_TIMEOUT         16
 #define WDT_MIN_TIMEOUT         1
 #define WDT_MODE_TIMEOUT(n)     ((n) << 3)
@@ -50,6 +49,7 @@ static unsigned int timeout = WDT_MAX_TIMEOUT;
 struct sunxi_wdt_dev {
         struct watchdog_device wdt_dev;
         void __iomem *wdt_base;
+        struct notifier_block restart_handler;
 };
 
 /*
@@ -74,24 +74,29 @@ static const int wdt_timeout_map[] = {
         [16] = 0xB, /* 16s */
 };
 
-static void __iomem *reboot_wdt_base;
 
-static void sun4i_wdt_restart(enum reboot_mode mode, const char *cmd)
+static int sunxi_restart_handle(struct notifier_block *this, unsigned long mode,
+                                void *cmd)
 {
+        struct sunxi_wdt_dev *sunxi_wdt = container_of(this,
+                                                       struct sunxi_wdt_dev,
+                                                       restart_handler);
+        void __iomem *wdt_base = sunxi_wdt->wdt_base;
+
         /* Enable timer and set reset bit in the watchdog */
-        writel(WDT_MODE_EN | WDT_MODE_RST_EN, reboot_wdt_base + WDT_MODE);
+        writel(WDT_MODE_EN | WDT_MODE_RST_EN, wdt_base + WDT_MODE);
 
         /*
          * Restart the watchdog. The default (and lowest) interval
          * value for the watchdog is 0.5s.
          */
-        writel(WDT_CTRL_RELOAD, reboot_wdt_base + WDT_CTRL);
+        writel(WDT_CTRL_RELOAD, wdt_base + WDT_CTRL);
 
         while (1) {
                 mdelay(5);
-                writel(WDT_MODE_EN | WDT_MODE_RST_EN,
-                       reboot_wdt_base + WDT_MODE);
+                writel(WDT_MODE_EN | WDT_MODE_RST_EN, wdt_base + WDT_MODE);
         }
+        return NOTIFY_DONE;
 }
 
 static int sunxi_wdt_ping(struct watchdog_device *wdt_dev)
@@ -205,8 +210,12 @@ static int sunxi_wdt_probe(struct platform_device *pdev)
         if (unlikely(err))
                 return err;
 
-        reboot_wdt_base = sunxi_wdt->wdt_base;
-        arm_pm_restart = sun4i_wdt_restart;
+        sunxi_wdt->restart_handler.notifier_call = sunxi_restart_handle;
+        sunxi_wdt->restart_handler.priority = 128;
+        err = register_restart_handler(&sunxi_wdt->restart_handler);
+        if (err)
+                dev_err(&pdev->dev,
+                        "cannot register restart handler (err=%d)\n", err);
 
         dev_info(&pdev->dev, "Watchdog enabled (timeout=%d sec, nowayout=%d)",
                         sunxi_wdt->wdt_dev.timeout, nowayout);
@@ -218,7 +227,7 @@ static int sunxi_wdt_remove(struct platform_device *pdev)
 {
         struct sunxi_wdt_dev *sunxi_wdt = platform_get_drvdata(pdev);
 
-        arm_pm_restart = NULL;
+        unregister_restart_handler(&sunxi_wdt->restart_handler);
 
         watchdog_unregister_device(&sunxi_wdt->wdt_dev);
         watchdog_set_drvdata(&sunxi_wdt->wdt_dev, NULL);
diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index 48bf152761c7..67fc8fcdc4b0 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -38,6 +38,9 @@ extern int reboot_force;
 extern int register_reboot_notifier(struct notifier_block *);
 extern int unregister_reboot_notifier(struct notifier_block *);
 
+extern int register_restart_handler(struct notifier_block *);
+extern int unregister_restart_handler(struct notifier_block *);
+extern void do_kernel_restart(char *cmd);
 
 /*
  * Architecture-specific implementations of sys_reboot commands.
diff --git a/kernel/reboot.c b/kernel/reboot.c
index a3a9e240fcdb..5925f5ae8dff 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -104,6 +104,87 @@ int unregister_reboot_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_reboot_notifier);
 
+/*
+ *      Notifier list for kernel code which wants to be called
+ *      to restart the system.
+ */
+static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
+
+/**
+ *      register_restart_handler - Register function to be called to reset
+ *                                 the system
+ *      @nb: Info about handler function to be called
+ *      @nb->priority:  Handler priority. Handlers should follow the
+ *                      following guidelines for setting priorities.
+ *                      0:      Restart handler of last resort,
+ *                              with limited restart capabilities
+ *                      128:    Default restart handler; use if no other
+ *                              restart handler is expected to be available,
+ *                              and/or if restart functionality is
+ *                              sufficient to restart the entire system
+ *                      255:    Highest priority restart handler, will
+ *                              preempt all other restart handlers
+ *
+ *      Registers a function with code to be called to restart the
+ *      system.
+ *
+ *      Registered functions will be called from machine_restart as last
+ *      step of the restart sequence (if the architecture specific
+ *      machine_restart function calls do_kernel_restart - see below
+ *      for details).
+ *      Registered functions are expected to restart the system immediately.
+ *      If more than one function is registered, the restart handler priority
+ *      selects which function will be called first.
+ *
+ *      Restart handlers are expected to be registered from non-architecture
+ *      code, typically from drivers. A typical use case would be a system
+ *      where restart functionality is provided through a watchdog. Multiple
+ *      restart handlers may exist; for example, one restart handler might
+ *      restart the entire system, while another only restarts the CPU.
+ *      In such cases, the restart handler which only restarts part of the
+ *      hardware is expected to register with low priority to ensure that
+ *      it only runs if no other means to restart the system is available.
+ *
+ *      Currently always returns zero, as atomic_notifier_chain_register()
+ *      always returns zero.
+ */
+int register_restart_handler(struct notifier_block *nb)
+{
+        return atomic_notifier_chain_register(&restart_handler_list, nb);
+}
+EXPORT_SYMBOL(register_restart_handler);
+
+/**
+ *      unregister_restart_handler - Unregister previously registered
+ *                                   restart handler
+ *      @nb: Hook to be unregistered
+ *
+ *      Unregisters a previously registered restart handler function.
+ *
+ *      Returns zero on success, or %-ENOENT on failure.
+ */
+int unregister_restart_handler(struct notifier_block *nb)
+{
+        return atomic_notifier_chain_unregister(&restart_handler_list, nb);
+}
+EXPORT_SYMBOL(unregister_restart_handler);
+
+/**
+ *      do_kernel_restart - Execute kernel restart handler call chain
+ *
+ *      Calls functions registered with register_restart_handler.
+ *
+ *      Expected to be called from machine_restart as last step of the restart
+ *      sequence.
+ *
+ *      Restarts the system immediately if a restart handler function has been
+ *      registered. Otherwise does nothing.
+ */
+void do_kernel_restart(char *cmd)
+{
+        atomic_notifier_call_chain(&restart_handler_list, reboot_mode, cmd);
+}
+
 void migrate_to_reboot_cpu(void)
 {
         /* The boot cpu is always logical cpu 0 */