watchdog: bcm2835: Support setting reboot partition

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>

diff --git a/drivers/watchdog/bcm2835_wdt.c b/drivers/watchdog/bcm2835_wdt.c
index c32c45bd8b097889c8f322255fa63c8ed507d6ab..ef02dfa23aa774e1cdf75f935c5de98535718767 100644 (file)
--- a/drivers/watchdog/bcm2835_wdt.c
+++ b/drivers/watchdog/bcm2835_wdt.c
@@ -35,13 +35,7 @@
 #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 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.
- */
-#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)
@@ -120,15 +114,28 @@ static struct watchdog_device bcm2835_wdt_wdd = {
        .timeout =      WDOG_TICKS_TO_SECS(PM_WDOG_TIME_SET),
 };
 
-static int
-bcm2835_restart(struct notifier_block *this, unsigned long mode, void *cmd)
+/*
+ * 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)
 {
-       struct bcm2835_wdt *wdt = container_of(this, struct bcm2835_wdt,
-                                              restart_handler);
-       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);
+
        val = readl_relaxed(wdt->base + PM_RSTC);
        val &= PM_RSTC_WRCFG_CLR;
        val |= PM_PASSWORD | PM_RSTC_WRCFG_FULL_RESET;
@@ -136,6 +143,20 @@ bcm2835_restart(struct notifier_block *this, unsigned long mode, void *cmd)
 
        /* No sleeping, possibly atomic. */
        mdelay(1);
+}
+
+static int bcm2835_restart_notifier_call(struct notifier_block *this,
+                                        unsigned long mode, void *cmd)
+{
+       struct bcm2835_wdt *wdt = container_of(this, struct bcm2835_wdt,
+                                              restart_handler);
+       unsigned long long val;
+       u8 partition = 0;
+
+       if (cmd && !kstrtoull(cmd, 0, &val) && val <= 63)
+               partition = val;
+
+       bcm2835_restart(wdt, partition);
 
        return 0;
 }
@@ -151,19 +172,9 @@ static void bcm2835_power_off(void)
                of_find_compatible_node(NULL, NULL, "brcm,bcm2835-pm-wdt");
        struct platform_device *pdev = of_find_device_by_node(np);
        struct bcm2835_wdt *wdt = platform_get_drvdata(pdev);
-       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->restart_handler, REBOOT_HARD, NULL);
+       /* Partition 63 tells the firmware that this is a halt */
+       bcm2835_restart(wdt, 63);
 }
 
 static int bcm2835_wdt_probe(struct platform_device *pdev)
@@ -208,7 +219,7 @@ static int bcm2835_wdt_probe(struct platform_device *pdev)
                return err;
        }
 
-       wdt->restart_handler.notifier_call = bcm2835_restart;
+       wdt->restart_handler.notifier_call = bcm2835_restart_notifier_call;
        wdt->restart_handler.priority = 128;
        register_restart_handler(&wdt->restart_handler);
        if (pm_power_off == NULL)