* [PATCH v3 1/2] dt-bindings: watchdog: Add Renesas WWDT
2025-10-17 10:15 [PATCH v3 0/2] watchdog: add Renesas Window Watchdog support Wolfram Sang
@ 2025-10-17 10:15 ` Wolfram Sang
2025-10-17 15:54 ` Conor Dooley
2025-10-17 10:15 ` [PATCH v3 2/2] watchdog: renesas_wwdt: add driver Wolfram Sang
1 sibling, 1 reply; 4+ messages in thread
From: Wolfram Sang @ 2025-10-17 10:15 UTC (permalink / raw)
To: linux-renesas-soc
Cc: Wolfram Sang, Wim Van Sebroeck, Guenter Roeck, Rob Herring,
Krzysztof Kozlowski, Conor Dooley, Geert Uytterhoeven,
Magnus Damm, linux-watchdog, devicetree
Describe the Window Watchdog Timer found on Renesas R-Car SoCs from late
Gen3 onwards.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
Note: Despite the name, V3U is considered to be a Gen4 SoC.
Changes since v2:
* none
Changes since v1:
* support not only V4H but all Gen3/4 SoCs having this WWDT
* handle the two-resets exception for V3U and S4
* switch order of clocks, so it is the same as for the resets
(for resets, "cnt" is always present and "bus" is optional)
* rename the file to match the base compatible
* require interrupts and resets
* drop unneeded label from the example
.../watchdog/renesas,rcar-gen3-wwdt.yaml | 114 ++++++++++++++++++
1 file changed, 114 insertions(+)
create mode 100644 Documentation/devicetree/bindings/watchdog/renesas,rcar-gen3-wwdt.yaml
diff --git a/Documentation/devicetree/bindings/watchdog/renesas,rcar-gen3-wwdt.yaml b/Documentation/devicetree/bindings/watchdog/renesas,rcar-gen3-wwdt.yaml
new file mode 100644
index 000000000000..ffafe9a6d3f5
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/renesas,rcar-gen3-wwdt.yaml
@@ -0,0 +1,114 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/renesas,rcar-gen3-wwdt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Renesas Window Watchdog Timer (WWDT) Controller
+
+maintainers:
+ - Wolfram Sang <wsa+renesas@sang-engineering.com>
+
+properties:
+ compatible:
+ oneOf:
+ - items:
+ - enum:
+ - renesas,r8a77970-wwdt # R-Car V3M
+ - renesas,r8a77980-wwdt # R-Car V3H
+ - const: renesas,rcar-gen3-wwdt
+
+ - items:
+ - enum:
+ - renesas,r8a779a0-wwdt # R-Car V3U
+ - renesas,r8a779f0-wwdt # R-Car S4
+ - renesas,r8a779g0-wwdt # R-Car V4H
+ - renesas,r8a779h0-wwdt # R-Car V4M
+ - const: renesas,rcar-gen4-wwdt
+
+ reg:
+ maxItems: 1
+
+ interrupts:
+ items:
+ - description: Pretimeout, 75% of overflow reached
+ - description: Error occurred
+
+ interrupt-names:
+ items:
+ - const: pretimeout
+ - const: error
+
+ clocks:
+ items:
+ - description: Counting clock
+ - description: Bus clock
+
+ clock-names:
+ items:
+ - const: cnt
+ - const: bus
+
+ resets:
+ minItems: 1
+ maxItems: 2
+
+ reset-names:
+ minItems: 1
+ items:
+ - const: cnt
+ - const: bus
+
+ power-domains:
+ maxItems: 1
+
+required:
+ - compatible
+ - reg
+ - interrupts
+ - interrupt-names
+ - clocks
+ - clock-names
+ - resets
+ - reset-names
+ - power-domains
+
+allOf:
+ - $ref: watchdog.yaml#
+
+ - if:
+ properties:
+ compatible:
+ contains:
+ enum:
+ - renesas,r8a779a0-wwdt
+ - renesas,r8a779f0-wwdt
+ then:
+ properties:
+ resets:
+ minItems: 2
+ reset-names:
+ minItems: 2
+
+additionalProperties: false
+
+examples:
+ - |
+ #include <dt-bindings/clock/r8a779g0-cpg-mssr.h>
+ #include <dt-bindings/power/r8a779g0-sysc.h>
+ #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+ watchdog@ffc90000 {
+ compatible = "renesas,r8a779g0-wwdt",
+ "renesas,rcar-gen4-wwdt";
+ reg = <0xffc90000 0x10>;
+ interrupts = <GIC_SPI 310 IRQ_TYPE_LEVEL_HIGH>,
+ <GIC_SPI 311 IRQ_TYPE_LEVEL_HIGH>;
+ interrupt-names = "pretimeout", "error";
+ clocks = <&cpg CPG_CORE R8A779G0_CLK_R>,
+ <&cpg CPG_CORE R8A779G0_CLK_SASYNCRT>;
+ clock-names = "cnt", "bus";
+ power-domains = <&sysc R8A779G0_PD_ALWAYS_ON>;
+ resets = <&cpg 1200>;
+ reset-names = "cnt";
+ };
--
2.47.2
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v3 2/2] watchdog: renesas_wwdt: add driver
2025-10-17 10:15 [PATCH v3 0/2] watchdog: add Renesas Window Watchdog support Wolfram Sang
2025-10-17 10:15 ` [PATCH v3 1/2] dt-bindings: watchdog: Add Renesas WWDT Wolfram Sang
@ 2025-10-17 10:15 ` Wolfram Sang
1 sibling, 0 replies; 4+ messages in thread
From: Wolfram Sang @ 2025-10-17 10:15 UTC (permalink / raw)
To: linux-renesas-soc
Cc: Wolfram Sang, Guenter Roeck, Wim Van Sebroeck, Geert Uytterhoeven,
Magnus Damm, linux-watchdog
This driver adds support for the Renesas Window Watchdog Timer (WWDT).
Because it can only be setup once after boot and we cannot know if this
already happened in early boot stages, it is mandated that the firmware
configures the watchdog. Linux then adapts according to the given
setup. Note that this watchdog only reports an overflow to the Error
Control Module (ECM) and does not reset the SoC on its own.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
---
Changes since v2:
* use container_of instead of drvdata (Guenter)
* explain ECM connection a little more
* added tag from Guenter (Thanks!)
Changes since v1:
* support not only V4H but all Gen3/4 SoCs having this WWDT
* update commit message and add introductory comment to explain how
this WWDT is handled as a "read-only" device basically
* dropped pretimeout flag because this feature cannot be configured
from userspace
* added bitfield.h to prevent build failures
* switched to "GPL" licence string
* cosmetic updates
drivers/watchdog/Kconfig | 8 ++
drivers/watchdog/Makefile | 1 +
drivers/watchdog/renesas_wwdt.c | 163 ++++++++++++++++++++++++++++++++
3 files changed, 172 insertions(+)
create mode 100644 drivers/watchdog/renesas_wwdt.c
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 05008d937e40..792d0d831336 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -969,6 +969,14 @@ config RENESAS_WDT
This driver adds watchdog support for the integrated watchdogs in the
Renesas R-Car and other SH-Mobile SoCs (usually named RWDT or SWDT).
+config RENESAS_WWDT
+ tristate "Renesas Window WWDT Watchdog"
+ depends on ARCH_RENESAS || COMPILE_TEST
+ select WATCHDOG_CORE
+ help
+ This driver adds watchdog support for a window timer found in some
+ Renesas R-Car Gen3 and later SoCs.
+
config RENESAS_RZAWDT
tristate "Renesas RZ/A WDT Watchdog"
depends on ARCH_RENESAS || COMPILE_TEST
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index b680e4d3c1bc..ba52099b1253 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -85,6 +85,7 @@ obj-$(CONFIG_DIGICOLOR_WATCHDOG) += digicolor_wdt.o
obj-$(CONFIG_LPC18XX_WATCHDOG) += lpc18xx_wdt.o
obj-$(CONFIG_BCM7038_WDT) += bcm7038_wdt.o
obj-$(CONFIG_RENESAS_WDT) += renesas_wdt.o
+obj-$(CONFIG_RENESAS_WWDT) += renesas_wwdt.o
obj-$(CONFIG_RENESAS_RZAWDT) += rza_wdt.o
obj-$(CONFIG_RENESAS_RZN1WDT) += rzn1_wdt.o
obj-$(CONFIG_RENESAS_RZG2LWDT) += rzg2l_wdt.o
diff --git a/drivers/watchdog/renesas_wwdt.c b/drivers/watchdog/renesas_wwdt.c
new file mode 100644
index 000000000000..b250913c349a
--- /dev/null
+++ b/drivers/watchdog/renesas_wwdt.c
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for the Renesas Window Watchdog Timer (WWDT)
+ *
+ * The WWDT can only be setup once after boot. Because we cannot know if this
+ * already happened in early boot stages, it is mandated that the firmware
+ * configures the watchdog. Linux then adapts according to the given setup.
+ * Note that this watchdog reports in the default configuration an overflow to
+ * the Error Control Module which then decides further actions. Or the WWDT is
+ * configured to generate an interrupt.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+#define WDTA0WDTE 0x00
+#define WDTA0RUN BIT(7)
+#define WDTA0_KEY 0x2c
+
+#define WDTA0MD 0x0c
+#define WDTA0OVF(x) FIELD_GET(GENMASK(6, 4), x)
+#define WDTA0WIE BIT(3)
+#define WDTA0ERM BIT(2)
+#define WDTA0WS(x) FIELD_GET(GENMASK(1, 0), x)
+
+struct wwdt_priv {
+ void __iomem *base;
+ struct watchdog_device wdev;
+};
+
+static int wwdt_start(struct watchdog_device *wdev)
+{
+ struct wwdt_priv *priv = container_of(wdev, struct wwdt_priv, wdev);
+
+ writeb(WDTA0RUN | WDTA0_KEY, priv->base + WDTA0WDTE);
+ return 0;
+}
+
+static const struct watchdog_info wwdt_ident = {
+ .options = WDIOF_KEEPALIVEPING | WDIOF_ALARMONLY,
+ .identity = "Renesas Window Watchdog",
+};
+
+static const struct watchdog_ops wwdt_ops = {
+ .owner = THIS_MODULE,
+ .start = wwdt_start,
+};
+
+static irqreturn_t wwdt_error_irq(int irq, void *dev_id)
+{
+ struct device *dev = dev_id;
+
+ dev_warn(dev, "Watchdog timed out\n");
+ return IRQ_HANDLED;
+}
+
+static irqreturn_t wwdt_pretimeout_irq(int irq, void *dev_id)
+{
+ struct watchdog_device *wdev = dev_id;
+
+ watchdog_notify_pretimeout(wdev);
+ return IRQ_HANDLED;
+}
+
+static int wwdt_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct wwdt_priv *priv;
+ struct watchdog_device *wdev;
+ struct clk *clk;
+ unsigned long rate;
+ unsigned int interval, window_size;
+ int ret;
+ u8 val;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(priv->base))
+ return PTR_ERR(priv->base);
+
+ clk = devm_clk_get(dev, "cnt");
+ if (IS_ERR(clk))
+ return PTR_ERR(clk);
+
+ rate = clk_get_rate(clk);
+ if (!rate)
+ return -EINVAL;
+
+ wdev = &priv->wdev;
+
+ val = readb(priv->base + WDTA0WDTE);
+ if (val & WDTA0RUN)
+ set_bit(WDOG_HW_RUNNING, &wdev->status);
+
+ val = readb(priv->base + WDTA0MD);
+ interval = 1 << (9 + WDTA0OVF(val));
+ /* size of the closed(!) window per mille */
+ window_size = 250 * (3 - WDTA0WS(val));
+
+ wdev->info = &wwdt_ident;
+ wdev->ops = &wwdt_ops;
+ wdev->parent = dev;
+ wdev->min_hw_heartbeat_ms = window_size * interval / rate;
+ wdev->max_hw_heartbeat_ms = 1000 * interval / rate;
+ wdev->timeout = DIV_ROUND_UP(wdev->max_hw_heartbeat_ms, 1000);
+ watchdog_set_nowayout(wdev, true);
+
+ if (!(val & WDTA0ERM)) {
+ ret = platform_get_irq_byname(pdev, "error");
+ if (ret < 0)
+ return ret;
+
+ ret = devm_request_threaded_irq(dev, ret, NULL, wwdt_error_irq,
+ IRQF_ONESHOT, NULL, dev);
+ if (ret < 0)
+ return ret;
+ }
+
+ if (val & WDTA0WIE) {
+ ret = platform_get_irq_byname(pdev, "pretimeout");
+ if (ret < 0)
+ return ret;
+
+ ret = devm_request_threaded_irq(dev, ret, NULL, wwdt_pretimeout_irq,
+ IRQF_ONESHOT, NULL, wdev);
+ if (ret < 0)
+ return ret;
+ }
+
+ devm_watchdog_register_device(dev, wdev);
+
+ return 0;
+}
+
+static const struct of_device_id renesas_wwdt_ids[] = {
+ { .compatible = "renesas,rcar-gen3-wwdt", },
+ { .compatible = "renesas,rcar-gen4-wwdt", },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, renesas_wwdt_ids);
+
+static struct platform_driver renesas_wwdt_driver = {
+ .driver = {
+ .name = "renesas_wwdt",
+ .of_match_table = renesas_wwdt_ids,
+ },
+ .probe = wwdt_probe,
+};
+module_platform_driver(renesas_wwdt_driver);
+
+MODULE_DESCRIPTION("Renesas Window Watchdog (WWDT) Driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Wolfram Sang <wsa+renesas@sang-engineering.com>");
--
2.47.2
^ permalink raw reply related [flat|nested] 4+ messages in thread