watchdog: add support for QCOM WDT

Add a driver for the watchdog timer block found in the Krait Processor Subsystem (KPSS) on the MSM8960, APQ8064, and IPQ8064.

Signed-off-by Josh Cartwright <[email protected]>

---
 drivers/watchdog/Kconfig    |  13 +++
 drivers/watchdog/Makefile   |   1 +
 drivers/watchdog/qcom-wdt.c | 189 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 203 insertions(+)
 create mode 100644 drivers/watchdog/qcom-wdt.c

drivers/watchdog/Kconfig +13 -0

index 79d2589..c389ed7 100644
@@ -421,6 +421,19 @@ config SIRFSOC_WATCHDOG
 	  Support for CSR SiRFprimaII and SiRFatlasVI watchdog. When
 	  the watchdog triggers the system will be reset.
 
+config QCOM_WDT
+	tristate "QCOM watchdog"
+	depends on HAS_IOMEM
+	depends on ARCH_QCOM
+	select WATCHDOG_CORE
+	help
+	  Say Y here to include Watchdog timer support for the watchdog found
+	  on QCOM chipsets.  Currently supported targets are the MSM8960,
+	  APQ8064, and IPQ8064.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called qcom_wdt.
+
 # AVR32 Architecture
 
 config AT32AP700X_WDT

drivers/watchdog/Makefile +1 -0

index 985a66c..cede21e 100644
@@ -57,6 +57,7 @@ obj-$(CONFIG_RETU_WATCHDOG) += retu_wdt.o
 obj-$(CONFIG_BCM2835_WDT) += bcm2835_wdt.o
 obj-$(CONFIG_MOXART_WDT) += moxart_wdt.o
 obj-$(CONFIG_SIRFSOC_WATCHDOG) += sirfsoc_wdt.o
+obj-$(CONFIG_QCOM_WDT) += qcom-wdt.o
 obj-$(CONFIG_BCM_KONA_WDT) += bcm_kona_wdt.o
 
 # AVR32 Architecture

drivers/watchdog/qcom-wdt.c new file +91 -0

new file mode 100644
index 0000000..0f56ca3
@@ -0,0 +1,189 @@
+/* Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+#include <linux/clk.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 WDT_RST		0x0
+#define WDT_EN		0x8
+#define WDT_BITE_TIME	0x24
+
+struct qcom_wdt {
+	struct watchdog_device	wdd;
+	struct clk		*clk;
+	unsigned long		rate;
+	void __iomem		*base;
+};
+
+static inline
+struct qcom_wdt *to_qcom_wdt(struct watchdog_device *wdd)
+{
+	return container_of(wdd, struct qcom_wdt, wdd);
+}
+
+static int qcom_wdt_start(struct watchdog_device *wdd)
+{
+	struct qcom_wdt *wdt = to_qcom_wdt(wdd);
+
+	writel(0, wdt->base + WDT_EN);
+	writel(1, wdt->base + WDT_RST);
+	writel(wdd->timeout * wdt->rate, wdt->base + WDT_BITE_TIME);
+	writel(1, wdt->base + WDT_EN);
+	return 0;
+}
+
+static int qcom_wdt_stop(struct watchdog_device *wdd)
+{
+	struct qcom_wdt *wdt = to_qcom_wdt(wdd);
+
+	writel(0, wdt->base + WDT_EN);
+	return 0;
+}
+
+static int qcom_wdt_ping(struct watchdog_device *wdd)
+{
+	struct qcom_wdt *wdt = to_qcom_wdt(wdd);
+
+	writel(1, wdt->base + WDT_RST);
+	return 0;
+}
+
+static int qcom_wdt_set_timeout(struct watchdog_device *wdd,
+				unsigned int timeout)
+{
+	wdd->timeout = timeout;
+	return qcom_wdt_start(wdd);
+}
+
+static const struct watchdog_ops qcom_wdt_ops = {
+	.start		= qcom_wdt_start,
+	.stop		= qcom_wdt_stop,
+	.ping		= qcom_wdt_ping,
+	.set_timeout	= qcom_wdt_set_timeout,
+	.owner		= THIS_MODULE,
+};
+
+static const struct watchdog_info qcom_wdt_info = {
+	.options	= WDIOF_KEEPALIVEPING
+			| WDIOF_MAGICCLOSE
+			| WDIOF_SETTIMEOUT,
+	.identity	= KBUILD_MODNAME,
+};
+
+static int qcom_wdt_probe(struct platform_device *pdev)
+{
+	struct qcom_wdt *wdt;
+	struct resource *res;
+	int ret;

drivers/watchdog/qcom-wdt.c new file +20 -0

+	}
+
+	/*
+	 * We use the clock rate to calculate the max timeout, so ensure it's
+	 * not zero to avoid a divide-by-zero exception.
+	 *
+	 * WATCHDOG_CORE assumes units of seconds, if the WDT is clocked such
+	 * that it would bite before a second elapses it's usefulness is
+	 * limited.  Bail if this is the case.
+	 */
+	wdt->rate = clk_get_rate(wdt->clk);
+	if (wdt->rate == 0 ||
+	    wdt->rate > 0x10000000U) {
+		dev_err(&pdev->dev, "invalid clock rate\n");
+		ret = -EINVAL;
+		goto err_clk_unprepare;
+	}
+
+	wdt->wdd.dev = &pdev->dev;
+	wdt->wdd.info = &qcom_wdt_info;

drivers/watchdog/qcom-wdt.c new file +46 -0

+	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
+
+	ret = watchdog_register_device(&wdt->wdd);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register watchdog\n");
+		goto err_clk_unprepare;
+	}
+
+	platform_set_drvdata(pdev, wdt);
+	return 0;
+
+err_clk_unprepare:
+	clk_disable_unprepare(wdt->clk);
+err_out:
+	return ret;
+}
+
+static int qcom_wdt_remove(struct platform_device *pdev)
+{
+	struct qcom_wdt *wdt = platform_get_drvdata(pdev);
+
+	watchdog_unregister_device(&wdt->wdd);
+	clk_disable_unprepare(wdt->clk);
+	return 0;
+}
+
+static const struct of_device_id qcom_wdt_of_table[] = {
+	{ .compatible = "qcom,kpss-wdt-msm8960", },
+	{ .compatible = "qcom,kpss-wdt-apq8064", },
+	{ .compatible = "qcom,kpss-wdt-ipq8064", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, qcom_wdt_of_table);
+
+static struct platform_driver qcom_watchdog_driver = {
+	.probe	= qcom_wdt_probe,
+	.remove	= qcom_wdt_remove,
+	.driver	= {
+		.name		= KBUILD_MODNAME,
+		.of_match_table	= qcom_wdt_of_table,
+	},
+};
+module_platform_driver(qcom_watchdog_driver);
+
+MODULE_DESCRIPTION("QCOM KPSS Watchdog Driver");
+MODULE_LICENSE("GPL v2");

Signature · 2 lines

Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

Quoted 4 lines · Josh Cartwright

Add a driver for the watchdog timer block found in the Krait Processor Subsystem (KPSS) on the MSM8960, APQ8064, and IPQ8064.

Signed-off-by Josh Cartwright <[email protected]>

Hi Josh,

just a couple of minor comments this time (yes, I know, I am being difficult ;-).

Quoted 1 line

+++ b/drivers/watchdog/qcom-wdt.c

Quoted 5 lines

drivers/watchdog/qcom-wdt.c new file +5 -0

+static int qcom_wdt_probe(struct platform_device *pdev)
+{
+	struct qcom_wdt *wdt;
+	struct resource *res;
+	int ret;

drivers/watchdog/qcom-wdt.c line 101

Quoted 10 lines

drivers/watchdog/qcom-wdt.c new file +10 -0

+
+	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	wdt->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(wdt->base)) {
+		ret = PTR_ERR(wdt->base);
+		goto err_out;

This is really unnecessary. Just return PTR_ERR((wdt->base) as you did before. No need to make the code more complicated than necessary.

Basic rule is: If you can return immediately, do it. Otherwise use goto and have a single error handler.

drivers/watchdog/qcom-wdt.c line 107

Quoted 6 lines

drivers/watchdog/qcom-wdt.c new file +6 -0

+	}
+
+	wdt->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(wdt->clk)) {
+		ret = PTR_ERR(wdt->clk);
+		goto err_out;

Same here.

drivers/watchdog/qcom-wdt.c line 113

Quoted 6 lines

drivers/watchdog/qcom-wdt.c new file +6 -0

+	}
+
+	ret = clk_prepare_enable(wdt->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to setup clock\n");
+		goto err_out;

and here.

The Qualcomm Krait Processor Sub-system (KPSS) contains one or more instances of the WDT. Provide documentation on how to describe these in the device tree.

Signed-off-by Josh Cartwright <[email protected]>

---
 .../devicetree/bindings/watchdog/qcom-wdt.txt      | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/qcom-wdt.txt

Documentation/devicetree/bindings/watchdog/qcom-wdt.txt new file +4 -0

new file mode 100644
index 0000000..c75566e
@@ -0,0 +1,22 @@
+Qualcomm Krait Processor Sub-system (KPSS) Watchdog
+---------------------------------------------------
+
+Required properties :

Documentation/devicetree/bindings/watchdog/qcom-wdt.txt new file +8 -0

+
+Example:
+	watchdog at 208a038 {
+		compatible = "qcom,kpss-wdt-ipq8064";
+		reg = <0x0208a038 0x40>;
+		clocks = <&sleep_clk>;
+		timeout-sec = <10>;
+	};

Signature · 2 lines

Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

On Thu, Sep 25, 2014 at 12:48:52PM -0500, Josh Cartwright wrote:

Quoted 2 lines

+- timeout-sec : shall contain the default watchdog timeout in seconds,
+                if unset, the default timeout is 30 seconds

Hi Josh,

timeout-sec is optional, not mandatory.

The WDT's BITE_TIME warm-reset behavior can be leveraged as a last resort mechanism for triggering chip reset. Usually, other restart methods (such as PS_HOLD) are preferrable for issuing a more complete reset of the chip. As such, keep the priority of the watchdog notifier low.

Signed-off-by Josh Cartwright <[email protected]>

---
 drivers/watchdog/qcom-wdt.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

drivers/watchdog/qcom-wdt.c +0 -0

index 0f56ca3..8ce339f 100644

drivers/watchdog/qcom-wdt.c +37 -0

 #include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/reboot.h>
 #include <linux/watchdog.h>
 
 #define WDT_RST		0x0

@@ -26,6 +28,7 @@ struct qcom_wdt {
 	struct watchdog_device	wdd;
 	struct clk		*clk;
 	unsigned long		rate;
+	struct notifier_block	restart_nb;
 	void __iomem		*base;
 };
 

@@ -84,6 +87,32 @@ static const struct watchdog_info qcom_wdt_info = {
 	.identity	= KBUILD_MODNAME,
 };
 
+static int qcom_wdt_restart(struct notifier_block *nb, unsigned long action,
+			    void *data)
+{
+	struct qcom_wdt *wdt = container_of(nb, struct qcom_wdt, restart_nb);
+	u32 timeout;
+
+	/*
+	 * Trigger watchdog bite:
+	 *    Setup BITE_TIME to be 128ms, and enable WDT.
+	 */
+	timeout = 128 * wdt->rate / 1000;
+
+	writel(0, wdt->base + WDT_EN);
+	writel(1, wdt->base + WDT_RST);
+	writel(timeout, wdt->base + WDT_BITE_TIME);
+	writel(1, wdt->base + WDT_EN);
+
+	/*
+	 * Actually make sure the above sequence hits hardware before sleeping.
+	 */
+	wmb();
+
+	msleep(150);
+	return NOTIFY_DONE;
+}
+
 static int qcom_wdt_probe(struct platform_device *pdev)
 {
 	struct qcom_wdt *wdt;

@@ -149,6 +178,14 @@ static int qcom_wdt_probe(struct platform_device *pdev)
 		goto err_clk_unprepare;
 	}
 
+	/*
+	 * WDT restart notifier has priority 0 (use as a last resort)
+	 */
+	wdt->restart_nb.notifier_call = qcom_wdt_restart;
+	ret = register_restart_handler(&wdt->restart_nb);
+	if (ret)
+		dev_err(&pdev->dev, "failed to setup restart handler\n");
+
 	platform_set_drvdata(pdev, wdt);
 	return 0;
 

@@ -162,6 +199,7 @@ static int qcom_wdt_remove(struct platform_device *pdev)
 {
 	struct qcom_wdt *wdt = platform_get_drvdata(pdev);
 
+	unregister_restart_handler(&wdt->restart_nb);
 	watchdog_unregister_device(&wdt->wdd);
 	clk_disable_unprepare(wdt->clk);
 	return 0;

Signature · 2 lines

Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

Quoted 11 lines · Josh Cartwright

The WDT's BITE_TIME warm-reset behavior can be leveraged as a last resort mechanism for triggering chip reset. Usually, other restart methods (such as PS_HOLD) are preferrable for issuing a more complete reset of the chip. As such, keep the priority of the watchdog notifier low.

Signed-off-by Josh Cartwright <[email protected]>

---
 drivers/watchdog/qcom-wdt.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

drivers/watchdog/qcom-wdt.c line 13

Quoted 9 lines

drivers/watchdog/qcom-wdt.c +1 -0

index 0f56ca3..8ce339f 100644
@@ -10,12 +10,14 @@
  * GNU General Public License for more details.
  *
  */
+#include <linux/delay.h>

Nitpick: Please keep alphabetical order of include files. That makes it easier to identify include files later on.