ARM: picoxcell: implement watchdog restart

Allow the platform to be restarted by triggering the watchdog to expire
with the shortest possible expiry.  This should reset the CPU core and
all on-chip peripherals.

v2:	- use writel_relaxed().

Signed-off-by: Jamie Iles <jamie@jamieiles.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/arch/arm/mach-picoxcell/common.c b/arch/arm/mach-picoxcell/common.c
index febee47bc116..a2e8ae8b5821 100644
--- a/arch/arm/mach-picoxcell/common.c
+++ b/arch/arm/mach-picoxcell/common.c
@@ -7,6 +7,7 @@
  *
  * All enquiries to support@picochip.com
  */
+#include <linux/delay.h>
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
 #include <linux/of.h>
@@ -23,6 +24,26 @@
 
 #include "common.h"
 
+#define WDT_CTRL_REG_EN_MASK    (1 << 0)
+#define WDT_CTRL_REG_OFFS       (0x00)
+#define WDT_TIMEOUT_REG_OFFS    (0x04)
+static void __iomem *wdt_regs;
+
+/*
+ * The machine restart method can be called from an atomic context so we won't
+ * be able to ioremap the regs then.
+ */
+static void picoxcell_setup_restart(void)
+{
+        struct device_node *np = of_find_compatible_node(NULL, NULL,
+                                                         "snps,dw-apb-wdg");
+        if (WARN(!np, "unable to setup watchdog restart"))
+                return;
+
+        wdt_regs = of_iomap(np, 0);
+        WARN(!wdt_regs, "failed to remap watchdog regs");
+}
+
 static struct map_desc io_map __initdata = {
         .virtual        = PHYS_TO_IO(PICOXCELL_PERIPH_BASE),
         .pfn            = __phys_to_pfn(PICOXCELL_PERIPH_BASE),
@@ -38,6 +59,7 @@ static void __init picoxcell_map_io(void)
 static void __init picoxcell_init_machine(void)
 {
         of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL);
+        picoxcell_setup_restart();
 }
 
 static const char *picoxcell_dt_match[] = {
@@ -56,6 +78,20 @@ static void __init picoxcell_init_irq(void)
         of_irq_init(vic_of_match);
 }
 
+static void picoxcell_wdt_restart(char mode, const char *cmd)
+{
+        /*
+         * Configure the watchdog to reset with the shortest possible timeout
+         * and give it chance to do the reset.
+         */
+        if (wdt_regs) {
+                writel_relaxed(WDT_CTRL_REG_EN_MASK, wdt_regs + WDT_CTRL_REG_OFFS);
+                writel_relaxed(0, wdt_regs + WDT_TIMEOUT_REG_OFFS);
+                /* No sleeping, possibly atomic. */
+                mdelay(500);
+        }
+}
+
 DT_MACHINE_START(PICOXCELL, "Picochip picoXcell")
         .map_io         = picoxcell_map_io,
         .nr_irqs        = NR_IRQS_LEGACY,
@@ -64,4 +100,5 @@ DT_MACHINE_START(PICOXCELL, "Picochip picoXcell")
         .timer          = &picoxcell_timer,
         .init_machine   = picoxcell_init_machine,
         .dt_compat      = picoxcell_dt_match,
+        .restart        = picoxcell_wdt_restart,
 MACHINE_END