From 351b9cbfc6aed837c7e23462d7109372de22e2bb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org>
Date: Fri, 7 Oct 2016 16:50:59 +0200
Subject: [PATCH] watchdog: bcm2835: Support setting reboot partition
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The Raspberry Pi firmware looks at the RSTS register to know which
partition to boot from. The reboot syscall command
LINUX_REBOOT_CMD_RESTART2 supports passing in a string argument.

Add support for passing in a partition number 0..63 to boot from.
Partition 63 is a special partiton indicating halt.
If the partition doesn't exist, the firmware falls back to partition 0.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
 drivers/watchdog/bcm2835_wdt.c | 49 +++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 22 deletions(-)

--- a/drivers/watchdog/bcm2835_wdt.c
+++ b/drivers/watchdog/bcm2835_wdt.c
@@ -32,13 +32,7 @@
 #define PM_RSTC_WRCFG_SET		0x00000030
 #define PM_RSTC_WRCFG_FULL_RESET	0x00000020
 #define PM_RSTC_RESET			0x00000102
-
-/*
- * 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
+#define PM_RSTS_PARTITION_CLR          0xfffffaaa
 
 #define SECS_TO_WDOG_TICKS(x) ((x) << 16)
 #define WDOG_TICKS_TO_SECS(x) ((x) >> 16)
@@ -97,9 +91,24 @@ static unsigned int bcm2835_wdt_get_time
 	return WDOG_TICKS_TO_SECS(ret & PM_WDOG_TIME_SET);
 }
 
-static void __bcm2835_restart(struct bcm2835_wdt *wdt)
+/*
+ * The Raspberry Pi firmware uses the RSTS register to know which partiton
+ * to boot from. The partiton value is spread into bits 0, 2, 4, 6, 8, 10.
+ * Partiton 63 is a special partition used by the firmware to indicate halt.
+ */
+
+static void __bcm2835_restart(struct bcm2835_wdt *wdt, u8 partition)
 {
-	u32 val;
+	u32 val, rsts;
+
+	rsts = (partition & BIT(0)) | ((partition & BIT(1)) << 1) |
+	       ((partition & BIT(2)) << 2) | ((partition & BIT(3)) << 3) |
+	       ((partition & BIT(4)) << 4) | ((partition & BIT(5)) << 5);
+
+	val = readl_relaxed(wdt->base + PM_RSTS);
+	val &= PM_RSTS_PARTITION_CLR;
+	val |= PM_PASSWORD | rsts;
+	writel_relaxed(val, wdt->base + PM_RSTS);
 
 	/* use a timeout of 10 ticks (~150us) */
 	writel_relaxed(10 | PM_PASSWORD, wdt->base + PM_WDOG);
@@ -117,7 +126,13 @@ static int bcm2835_restart(struct watchd
 {
 	struct bcm2835_wdt *wdt = watchdog_get_drvdata(wdog);
 
-	__bcm2835_restart(wdt);
+	unsigned long long val;
+	u8 partition = 0;
+
+	if (data && !kstrtoull(data, 0, &val) && val <= 63)
+		partition = val;
+
+	__bcm2835_restart(wdt, partition);
 
 	return 0;
 }
@@ -152,19 +167,9 @@ static struct watchdog_device bcm2835_wd
 static void bcm2835_power_off(void)
 {
 	struct bcm2835_wdt *wdt = bcm2835_power_off_wdt;
-	u32 val;
-
-	/*
-	 * We set the watchdog hard reset bit here to distinguish this reset
-	 * from the normal (full) reset. bootcode.bin will not reboot after a
-	 * hard reset.
-	 */
-	val = readl_relaxed(wdt->base + PM_RSTS);
-	val |= PM_PASSWORD | PM_RSTS_RASPBERRYPI_HALT;
-	writel_relaxed(val, wdt->base + PM_RSTS);
 
-	/* Continue with normal reset mechanism */
-	__bcm2835_restart(wdt);
+	/* Partition 63 tells the firmware that this is a halt */
+	__bcm2835_restart(wdt, 63);
 }
 
 static int bcm2835_wdt_probe(struct platform_device *pdev)
