[PATCH v3] watchdog: Add a watchdog driver for Raspberry Pi boards

* [PATCH v3] watchdog: Add a watchdog driver for Raspberry Pi boards
@ 2023-01-25  9:57 ETIENNE DUBLE
  2023-01-26  6:28 ` Stefan Roese
  2023-04-20 10:02 ` Stefan Roese
  0 siblings, 2 replies; 3+ messages in thread
From: ETIENNE DUBLE @ 2023-01-25  9:57 UTC (permalink / raw)
  To: Stefan Roese, u-boot

This driver supports the bcm2835 watchdog found on
Raspberry Pi boards.
It is derived from the Linux driver and was tested
on two Raspberry Pi board versions (B+ and 3B+).

Signed-off-by: Etienne Dublé <etienne.duble@imag.fr>
---
Changes for v2:
- fixed whitespaces in email
- moved a static variable to the priv struct
Changes for v3:
- used the max timeout value the hardware supports
- turned the warning to a one-line message

 drivers/watchdog/Kconfig       |   9 +++
 drivers/watchdog/Makefile      |   1 +
 drivers/watchdog/bcm2835_wdt.c | 132 +++++++++++++++++++++++++++++++++
 3 files changed, 142 insertions(+)
 create mode 100644 drivers/watchdog/bcm2835_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index f1b1cf63ca..06c0d630c8 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -30,6 +30,7 @@ config WATCHDOG_TIMEOUT_MSECS
 	default 128000 if ARCH_MX7 || ARCH_VF610
 	default 30000 if ARCH_SOCFPGA
 	default 16000 if ARCH_SUNXI
+	default 15000 if ARCH_BCM283X
 	default 60000
 	help
 	  Watchdog timeout in msec
@@ -326,6 +327,14 @@ config WDT_SUNXI
 	help
 	  Enable support for the watchdog timer in Allwinner sunxi SoCs.
 
+config WDT_BCM2835
+	bool "Broadcom 2835 watchdog timer support"
+	depends on WDT && ARCH_BCM283X
+	default y
+	help
+	  Enable support for the watchdog timer in Broadcom 283X SoCs such
+	  as Raspberry Pi boards.
+
 config XILINX_TB_WATCHDOG
 	bool "Xilinx Axi watchdog timer support"
 	depends on WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 446d961d7d..f99915960c 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_WDT_APPLE) += apple_wdt.o
 obj-$(CONFIG_WDT_ARMADA_37XX) += armada-37xx-wdt.o
 obj-$(CONFIG_WDT_ASPEED) += ast_wdt.o
 obj-$(CONFIG_WDT_AST2600) += ast2600_wdt.o
+obj-$(CONFIG_WDT_BCM2835) += bcm2835_wdt.o
 obj-$(CONFIG_WDT_BCM6345) += bcm6345_wdt.o
 obj-$(CONFIG_WDT_BOOKE) += booke_wdt.o
 obj-$(CONFIG_WDT_CORTINA) += cortina_wdt.o
diff --git a/drivers/watchdog/bcm2835_wdt.c b/drivers/watchdog/bcm2835_wdt.c
new file mode 100644
index 0000000000..3c1ead3dda
--- /dev/null
+++ b/drivers/watchdog/bcm2835_wdt.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2013 Lubomir Rintel <lkundrak@v3.sk>
+ * Copyright (C) 2023 Etienne Dublé (CNRS) <etienne.duble@imag.fr>
+ *
+ * This code is mostly derived from the linux driver.
+ */
+
+#include <dm.h>
+#include <wdt.h>
+#include <asm/io.h>
+#include <linux/delay.h>
+
+#define PM_RSTC					0x1c
+#define PM_WDOG					0x24
+
+#define PM_PASSWORD				0x5a000000
+
+/* The hardware supports a maximum timeout value of 0xfffff ticks
+ * (just below 16 seconds).
+ */
+#define PM_WDOG_MAX_TICKS			0x000fffff
+#define PM_RSTC_WRCFG_CLR			0xffffffcf
+#define PM_RSTC_WRCFG_FULL_RESET		0x00000020
+#define PM_RSTC_RESET				0x00000102
+
+#define MS_TO_WDOG_TICKS(x) (((x) << 16) / 1000)
+
+struct bcm2835_wdt_priv {
+	void __iomem *base;
+	u64 timeout_ticks;
+};
+
+static int bcm2835_wdt_start_ticks(struct udevice *dev,
+				   u64 timeout_ticks, ulong flags)
+{
+	struct bcm2835_wdt_priv *priv = dev_get_priv(dev);
+	void __iomem *base = priv->base;
+	u32 cur;
+
+	writel(PM_PASSWORD | timeout_ticks, base + PM_WDOG);
+	cur = readl(base + PM_RSTC);
+	writel(PM_PASSWORD | (cur & PM_RSTC_WRCFG_CLR) | PM_RSTC_WRCFG_FULL_RESET,
+	       base + PM_RSTC);
+
+	return 0;
+}
+
+static int bcm2835_wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
+{
+	struct bcm2835_wdt_priv *priv = dev_get_priv(dev);
+
+	priv->timeout_ticks = MS_TO_WDOG_TICKS(timeout_ms);
+
+	if (priv->timeout_ticks > PM_WDOG_MAX_TICKS) {
+		printf("bcm2835_wdt: the timeout value is too high, using ~16s instead.\n");
+		priv->timeout_ticks = PM_WDOG_MAX_TICKS;
+	}
+
+	return bcm2835_wdt_start_ticks(dev, priv->timeout_ticks, flags);
+}
+
+static int bcm2835_wdt_reset(struct udevice *dev)
+{
+	struct bcm2835_wdt_priv *priv = dev_get_priv(dev);
+
+	/* restart the timer with the value of priv->timeout_ticks
+	 * saved from the last bcm2835_wdt_start() call.
+	 */
+	return bcm2835_wdt_start_ticks(dev, priv->timeout_ticks, 0);
+}
+
+static int bcm2835_wdt_stop(struct udevice *dev)
+{
+	struct bcm2835_wdt_priv *priv = dev_get_priv(dev);
+	void __iomem *base = priv->base;
+
+	writel(PM_PASSWORD | PM_RSTC_RESET, base + PM_RSTC);
+
+	return 0;
+}
+
+static int bcm2835_wdt_expire_now(struct udevice *dev, ulong flags)
+{
+	int ret;
+
+	/* use a timeout of 10 ticks (~150us) */
+	ret = bcm2835_wdt_start_ticks(dev, 10, flags);
+	if (ret)
+		return ret;
+
+	mdelay(500);
+
+	return 0;
+}
+
+static const struct wdt_ops bcm2835_wdt_ops = {
+	.reset		= bcm2835_wdt_reset,
+	.start		= bcm2835_wdt_start,
+	.stop		= bcm2835_wdt_stop,
+	.expire_now	= bcm2835_wdt_expire_now,
+};
+
+static const struct udevice_id bcm2835_wdt_ids[] = {
+	{ .compatible = "brcm,bcm2835-pm" },
+	{ .compatible = "brcm,bcm2835-pm-wdt" },
+	{ /* sentinel */ }
+};
+
+static int bcm2835_wdt_probe(struct udevice *dev)
+{
+	struct bcm2835_wdt_priv *priv = dev_get_priv(dev);
+
+	priv->base = dev_remap_addr(dev);
+	if (!priv->base)
+		return -EINVAL;
+
+	priv->timeout_ticks = PM_WDOG_MAX_TICKS;
+
+	bcm2835_wdt_stop(dev);
+
+	return 0;
+}
+
+U_BOOT_DRIVER(bcm2835_wdt) = {
+	.name		= "bcm2835_wdt",
+	.id		= UCLASS_WDT,
+	.of_match	= bcm2835_wdt_ids,
+	.probe		= bcm2835_wdt_probe,
+	.priv_auto	= sizeof(struct bcm2835_wdt_priv),
+	.ops		= &bcm2835_wdt_ops,
+};
-- 
2.34.1

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