[PATCH] ARM: bcm2835: implement machine restart hook

[PATCH] ARM: bcm2835: implement machine restart hook

[Stephen Warren]

Implement the machine restart hook using the SoC's watchdog timer module.
To support this, define a DT binding for the watchdog module, and add it
to the device tree.

The downstream rpi-split branch contains a full watchdog timer driver
implementation, which also implements the restart hook. However, the
restart function is largely separate from the watchdog driver, so for
simplicity, the restart hook is implemented here directly in the main
machine source file.

Overall structure (separate setup/restart) functions derived from the
picoxcell ARM support.

Watchdog register IO sequence taken from code by Simon Arlott. Note that
the watchdog module is not documented in BCM2835-ARM-Peripherals.pdf.

Signed-off-by: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
---
 .../bindings/watchdog/brcm,bcm2835-pm-wdog.txt     |   13 ++++++
 arch/arm/boot/dts/bcm2835.dtsi                     |    5 +++
 arch/arm/mach-bcm2835/bcm2835.c                    |   46 ++++++++++++++++++++
 3 files changed, 64 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/brcm,bcm2835-pm-wdog.txt

diff --git a/Documentation/devicetree/bindings/watchdog/brcm,bcm2835-pm-wdog.txt b/Documentation/devicetree/bindings/watchdog/brcm,bcm2835-pm-wdog.txt
new file mode 100644
index 0000000..03138e6
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/brcm,bcm2835-pm-wdog.txt
@@ -0,0 +1,13 @@
+BCM2835 Watchdog timer
+
+Required properties:
+
+- compatible : should be "brcm,bcm2835-pm-wdog"
+- reg : Specifies base physical address and size of the registers.
+
+Example:
+
+intc: interrupt-controller {
+	compatible = "brcm,bcm2835-pm-wdog";
+	reg = <0x7e100000 0x28>;
+};
diff --git a/arch/arm/boot/dts/bcm2835.dtsi b/arch/arm/boot/dts/bcm2835.dtsi
index 0b61939..7e0d515 100644
--- a/arch/arm/boot/dts/bcm2835.dtsi
+++ b/arch/arm/boot/dts/bcm2835.dtsi
@@ -29,6 +29,11 @@
 			#interrupt-cells = <2>;
 		};
 
+		watchdog {
+			compatible = "brcm,bcm2835-pm-wdog";
+			reg = <0x7e100000 0x28>;
+		};
+
 		uart@20201000 {
 			compatible = "brcm,bcm2835-pl011", "arm,pl011", "arm,primecell";
 			reg = <0x7e201000 0x1000>;
diff --git a/arch/arm/mach-bcm2835/bcm2835.c b/arch/arm/mach-bcm2835/bcm2835.c
index f6fea49..35859c6 100644
--- a/arch/arm/mach-bcm2835/bcm2835.c
+++ b/arch/arm/mach-bcm2835/bcm2835.c
@@ -12,8 +12,10 @@
  * GNU General Public License for more details.
  */
 
+#include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/irqchip/bcm2835.h>
+#include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/bcm2835_timer.h>
 #include <linux/clk/bcm2835.h>
@@ -23,6 +25,48 @@
 
 #include <mach/bcm2835_soc.h>
 
+#define PM_RSTC				0x1c
+#define PM_WDOG				0x24
+
+#define PM_PASSWORD			0x5a000000
+#define PM_RSTC_WRCFG_MASK		0x00000030
+#define PM_RSTC_WRCFG_FULL_RESET	0x00000020
+
+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 bcm2835_setup_restart(void)
+{
+	struct device_node *np = of_find_compatible_node(NULL, NULL,
+						"brcm,bcm2835-pm-wdog");
+	if (WARN(!np, "unable to setup watchdog restart"))
+		return;
+
+	wdt_regs = of_iomap(np, 0);
+	WARN(!wdt_regs, "failed to remap watchdog regs");
+}
+
+static void bcm2835_restart(char mode, const char *cmd)
+{
+	u32 val;
+
+	if (!wdt_regs)
+		return;
+
+	/* use a timeout of 10 ticks (~150us) */
+	writel_relaxed(10 | PM_PASSWORD, wdt_regs + PM_WDOG);
+	val = readl_relaxed(wdt_regs + PM_RSTC);
+	val &= ~PM_RSTC_WRCFG_MASK;
+	val |= PM_PASSWORD | PM_RSTC_WRCFG_FULL_RESET;
+	writel_relaxed(val, wdt_regs + PM_RSTC);
+
+	/* No sleeping, possibly atomic. */
+	mdelay(1);
+}
+
 static struct map_desc io_map __initdata = {
 	.virtual = BCM2835_PERIPH_VIRT,
 	.pfn = __phys_to_pfn(BCM2835_PERIPH_PHYS),
@@ -39,6 +83,7 @@ void __init bcm2835_init(void)
 {
 	int ret;
 
+	bcm2835_setup_restart();
 	bcm2835_init_clocks();
 
 	ret = of_platform_populate(NULL, of_default_bus_match_table, NULL,
@@ -60,5 +105,6 @@ DT_MACHINE_START(BCM2835, "BCM2835")
 	.handle_irq = bcm2835_handle_irq,
 	.init_machine = bcm2835_init,
 	.timer = &bcm2835_timer,
+	.restart = bcm2835_restart,
 	.dt_compat = bcm2835_compat
 MACHINE_END
-- 
1.7.9.5

Re: [PATCH] ARM: bcm2835: implement machine restart hook

[Thomas Petazzoni]

Stephen,

On Thu, 27 Sep 2012 22:08:00 -0600, Stephen Warren wrote:

> +intc: interrupt-controller {

Isn't this a bizarre name for a watchdog device?

> +	compatible = "brcm,bcm2835-pm-wdog";
> +	reg = <0x7e100000 0x28>;
> +};

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

Re: [PATCH] ARM: bcm2835: implement machine restart hook

[Stephen Warren]

On 09/28/2012 04:15 AM, Thomas Petazzoni wrote:
> Stephen,
> 
> On Thu, 27 Sep 2012 22:08:00 -0600, Stephen Warren wrote:
> 
>> +intc: interrupt-controller {
> 
> Isn't this a bizarre name for a watchdog device?

Yes, certainly! It looks like I only made this cut/paste mistake in the
binding document, which is why the code actually worked...

>> +	compatible = "brcm,bcm2835-pm-wdog";
>> +	reg = <0x7e100000 0x28>;
>> +};

Re: [PATCH] ARM: bcm2835: implement machine restart hook

[Jean-Christophe PLAGNIOL-VILLARD]

On 22:08 Thu 27 Sep     , Stephen Warren wrote:
> Implement the machine restart hook using the SoC's watchdog timer module.
> To support this, define a DT binding for the watchdog module, and add it
> to the device tree.
> 
> The downstream rpi-split branch contains a full watchdog timer driver
> implementation, which also implements the restart hook. However, the
> restart function is largely separate from the watchdog driver, so for
> simplicity, the restart hook is implemented here directly in the main
> machine source file.
> 
> Overall structure (separate setup/restart) functions derived from the
> picoxcell ARM support.
> 
> Watchdog register IO sequence taken from code by Simon Arlott. Note that
> the watchdog module is not documented in BCM2835-ARM-Peripherals.pdf.
> 
> Signed-off-by: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
> ---
>  .../bindings/watchdog/brcm,bcm2835-pm-wdog.txt     |   13 ++++++
>  arch/arm/boot/dts/bcm2835.dtsi                     |    5 +++
>  arch/arm/mach-bcm2835/bcm2835.c                    |   46 ++++++++++++++++++++
>  3 files changed, 64 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/watchdog/brcm,bcm2835-pm-wdog.txt
> 
> diff --git a/Documentation/devicetree/bindings/watchdog/brcm,bcm2835-pm-wdog.txt b/Documentation/devicetree/bindings/watchdog/brcm,bcm2835-pm-wdog.txt
> new file mode 100644
> index 0000000..03138e6
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/watchdog/brcm,bcm2835-pm-wdog.txt
> @@ -0,0 +1,13 @@
> +BCM2835 Watchdog timer
> +
> +Required properties:
> +
> +- compatible : should be "brcm,bcm2835-pm-wdog"
> +- reg : Specifies base physical address and size of the registers.
> +
> +Example:
> +
> +intc: interrupt-controller {
> +	compatible = "brcm,bcm2835-pm-wdog";
it's seems everyone use -wdt

Best Regards,
J.

Re: [PATCH] ARM: bcm2835: implement machine restart hook

[Stephen Warren]

On 09/28/2012 04:31 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 22:08 Thu 27 Sep     , Stephen Warren wrote:
>> Implement the machine restart hook using the SoC's watchdog timer module.
>> To support this, define a DT binding for the watchdog module, and add it
>> to the device tree.
>>
>> The downstream rpi-split branch contains a full watchdog timer driver
>> implementation, which also implements the restart hook. However, the
>> restart function is largely separate from the watchdog driver, so for
>> simplicity, the restart hook is implemented here directly in the main
>> machine source file.

>> +++ b/Documentation/devicetree/bindings/watchdog/brcm,bcm2835-pm-wdog.txt

>> +Example:
>> +
>> +intc: interrupt-controller {
>> +	compatible = "brcm,bcm2835-pm-wdog";
>
> it's seems everyone use -wdt

That is true. "-wdog" is what was in the downstream patch, but I guess
it makes sense to fix it up to be consistent with everything already in
the kernel.

Re: [PATCH] ARM: bcm2835: implement machine restart hook

[Stephen Warren]

On 09/27/2012 10:08 PM, Stephen Warren wrote:
> Implement the machine restart hook using the SoC's watchdog timer module.
> To support this, define a DT binding for the watchdog module, and add it
> to the device tree.
> 
> The downstream rpi-split branch contains a full watchdog timer driver
> implementation, which also implements the restart hook. However, the
> restart function is largely separate from the watchdog driver, so for
> simplicity, the restart hook is implemented here directly in the main
> machine source file.
> 
> Overall structure (separate setup/restart) functions derived from the
> picoxcell ARM support.
> 
> Watchdog register IO sequence taken from code by Simon Arlott. Note that
> the watchdog module is not documented in BCM2835-ARM-Peripherals.pdf.

Applied to rpi's for-3.8/soc branch.