[PATCH 1/2] watchdog: bcm2835: add support for powering off SoC

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

The watchdog peripheral on the Raspberry Pi can be used to shutdown by
writing a magic value that the firmware checks for and rebooting.

This is useful to close an emulated Raspberry Pi in QEMU, so add
support.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/watchdog/bcm2835_wdt.c | 21 +++++++++++++++++++++
 include/soc/bcm283x/wdt.h      |  7 +++++++
 2 files changed, 28 insertions(+)

diff --git a/drivers/watchdog/bcm2835_wdt.c b/drivers/watchdog/bcm2835_wdt.c
index 874315d502a9..5b854c49b311 100644
--- a/drivers/watchdog/bcm2835_wdt.c
+++ b/drivers/watchdog/bcm2835_wdt.c
@@ -8,6 +8,7 @@
 #include <init.h>
 #include <io.h>
 #include <restart.h>
+#include <poweroff.h>
 #include <watchdog.h>
 
 #include <soc/bcm283x/wdt.h>
@@ -23,6 +24,7 @@ struct bcm2835_wd {
 	void __iomem *base;
 	struct device *dev;
 	struct restart_handler restart;
+	struct poweroff_handler poweroff;
 };
 
 #define RESET_TIMEOUT 10
@@ -41,6 +43,20 @@ static void __noreturn bcm2835_restart_soc(struct restart_handler *rst)
 	hang();
 }
 
+static void __noreturn bcm2835_poweroff_soc(struct poweroff_handler *poweroff)
+{
+	struct bcm2835_wd *priv = container_of(poweroff, struct bcm2835_wd, poweroff);
+	uint32_t val;
+
+	shutdown_barebox();
+
+	val = readl_relaxed(priv->base + PM_RSTS);
+	val |= PM_PASSWORD | PM_RSTS_RASPBERRYPI_HALT;
+	writel_relaxed(val, priv->base + PM_RSTS);
+
+	bcm2835_restart_soc(&priv->restart);
+}
+
 static int bcm2835_wd_set_timeout(struct watchdog *wd, unsigned timeout)
 {
 	struct bcm2835_wd *priv = container_of(wd, struct bcm2835_wd, wd);
@@ -86,6 +102,11 @@ static int bcm2835_wd_probe(struct device *dev)
 		}
 	}
 
+	priv->poweroff.name = "bcm2835_wd";
+	priv->poweroff.poweroff = bcm2835_poweroff_soc;
+
+	poweroff_handler_register(&priv->poweroff);
+
 	priv->restart.name = "bcm2835_wd";
 	priv->restart.restart = bcm2835_restart_soc;
 
diff --git a/include/soc/bcm283x/wdt.h b/include/soc/bcm283x/wdt.h
index 2002647b9c39..86e02bcf40f7 100644
--- a/include/soc/bcm283x/wdt.h
+++ b/include/soc/bcm283x/wdt.h
@@ -38,4 +38,11 @@
 #define PM_RSTS_HADSR_SET \
 	(PM_RSTS_HADSRQ_SET | PM_RSTS_HADSRF_SET | PM_RSTS_HADSRH_SET)
 
+/*
+ * The Raspberry Pi firmware uses the RSTS register to know which partition
+ * to boot from. The partition value is spread into bits 0, 2, 4, 6, 8, 10.
+ * Partition 63 is a special partition used by the firmware to indicate halt.
+ */
+#define PM_RSTS_RASPBERRYPI_HALT	0x555
+
 #endif
-- 
2.39.2