watchdog: Add booke watchdog driver

Add a driver for the PowerPC Book E watchdog driver that is present on a
number of Freescale/NXP SoCs.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>

drivers/watchdog/Kconfig

@@ -124,6 +124,13 @@ config WDT_BCM6345
 	  The watchdog timer is stopped when initialized.
 	  It performs full SoC reset.
 
+config WDT_BOOKE
+	bool "PowerPC Book-E watchdog driver"
+	depends on WDT && MPC85xx
+	help
+	  Watchdog driver for PowerPC Book-E chips, such as the Freescale
+	  MPC85xx SOCs and the IBM PowerPC 440.
+
 config WDT_CDNS
 	bool "Cadence watchdog timer support"
 	depends on WDT

drivers/watchdog/Makefile

@@ -21,6 +21,7 @@ obj-$(CONFIG_WDT_ARMADA_37XX) += armada-37xx-wdt.o
 obj-$(CONFIG_WDT_ASPEED) += ast_wdt.o
 obj-$(CONFIG_WDT_AST2600) += ast2600_wdt.o
 obj-$(CONFIG_WDT_BCM6345) += bcm6345_wdt.o
+obj-$(CONFIG_WDT_BOOKE) += booke_wdt.o
 obj-$(CONFIG_WDT_CORTINA) += cortina_wdt.o
 obj-$(CONFIG_WDT_ORION) += orion_wdt.o
 obj-$(CONFIG_WDT_CDNS) += cdns_wdt.o

drivers/watchdog/booke_wdt.c

@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Watchdog timer for PowerPC Book-E systems
+ */
+
+#include <div64.h>
+#include <dm.h>
+#include <wdt.h>
+#include <asm/processor.h>
+
+#define WDTP_MASK TCR_WP(0x3f)
+
+/* For the specified period, determine the number of seconds
+ * corresponding to the reset time.  There will be a watchdog
+ * exception at approximately 3/5 of this time.
+ *
+ * The formula to calculate this is given by:
+ * 2.5 * (2^(63-period+1)) / timebase_freq
+ *
+ * In order to simplify things, we assume that period is
+ * at least 1.  This will still result in a very long timeout.
+ */
+static unsigned long long period_to_sec(unsigned int period)
+{
+	unsigned long long tmp = 1ULL << (64 - period);
+	unsigned long tmp2 = get_tbclk();
+
+	/* tmp may be a very large number and we don't want to overflow,
+	 * so divide the timebase freq instead of multiplying tmp
+	 */
+	tmp2 = tmp2 / 5 * 2;
+
+	do_div(tmp, tmp2);
+	return tmp;
+}
+
+/*
+ * This procedure will find the highest period which will give a timeout
+ * greater than the one required. e.g. for a bus speed of 66666666 and
+ * and a parameter of 2 secs, then this procedure will return a value of 38.
+ */
+static unsigned int sec_to_period(unsigned int secs)
+{
+	unsigned int period;
+
+	for (period = 63; period > 0; period--) {
+		if (period_to_sec(period) >= secs)
+			return period;
+	}
+	return 0;
+}
+
+static int booke_wdt_reset(struct udevice *dev)
+{
+	mtspr(SPRN_TSR, TSR_ENW | TSR_WIS);
+
+	return 0;
+}
+
+static int booke_wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
+{
+	u32 val;
+	unsigned int timeout = DIV_ROUND_UP(timeout_ms, 1000);
+
+	/* clear status before enabling watchdog */
+	booke_wdt_reset(dev);
+	val = mfspr(SPRN_TCR);
+	val &= ~WDTP_MASK;
+	val |= (TCR_WIE | TCR_WRC(WRC_CHIP) | TCR_WP(sec_to_period(timeout)));
+
+	mtspr(SPRN_TCR, val);
+
+	return 0;
+}
+
+static int booke_wdt_stop(struct udevice *dev)
+{
+	u32 val;
+
+	val = mfspr(SPRN_TCR);
+	val &= ~(TCR_WIE | WDTP_MASK);
+	mtspr(SPRN_TCR, val);
+
+	/* clear status to make sure nothing is pending */
+	booke_wdt_reset(dev);
+
+	return 0;
+}
+
+static const struct wdt_ops booke_wdt_ops = {
+	.start = booke_wdt_start,
+	.stop = booke_wdt_stop,
+	.reset = booke_wdt_reset,
+};
+
+static const struct udevice_id booke_wdt_ids[] = {
+	{ .compatible = "fsl,booke-wdt" },
+	{}
+};
+
+U_BOOT_DRIVER(booke_wdt) = {
+	.name = "booke_wdt",
+	.id = UCLASS_WDT,
+	.of_match = booke_wdt_ids,
+	.ops = &booke_wdt_ops,
+};