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 | 176 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 190 insertions(+)
 create mode 100644 drivers/watchdog/qcom-wdt.c

drivers/watchdog/Kconfig +13 -0

index 1d1330a..0479e3f 100644
@@ -443,6 +443,19 @@ config TEGRA_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called tegra_wdt.
 
+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 468c320..d645448 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
 obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
 

drivers/watchdog/qcom-wdt.c new file +113 -0

new file mode 100644
index 0000000..d5e46e2
@@ -0,0 +1,176 @@
+/* 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;
+	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);
+	unsigned long bite_time;
+
+	bite_time = wdd->timeout * clk_get_rate(wdt->clk);
+
+	writel(0, wdt->base + WDT_EN);
+	writel(1, wdt->base + WDT_RST);
+	writel(bite_time, 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;
+	unsigned long freq;
+	int ret;
+
+	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))
+		return PTR_ERR(wdt->base);
+
+	wdt->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(wdt->clk))
+		return PTR_ERR(wdt->clk);
+
+	ret = clk_prepare_enable(wdt->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to setup clock\n");
+		return ret;
+	}

drivers/watchdog/qcom-wdt.c new file +36 -0

+		return ret;
+	}
+
+	platform_set_drvdata(pdev, wdt);
+	return 0;
+}
+
+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 · 7 lines

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hosted by The Linux Foundation

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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,

looks much better. Couple of comments inline.

Quoted 19 lines

+++ b/drivers/watchdog/Kconfig

drivers/watchdog/Kconfig +13 -0

@@ -443,6 +443,19 @@ config TEGRA_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called tegra_wdt.
 
+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

Quoted 29 lines

drivers/watchdog/qcom-wdt.c new file +29 -0

+static int qcom_wdt_probe(struct platform_device *pdev)
+{
+	struct qcom_wdt *wdt;
+	struct resource *res;
+	unsigned long freq;
+	int ret;
+
+	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))
+		return PTR_ERR(wdt->base);
+
+	wdt->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(wdt->clk))
+		return PTR_ERR(wdt->clk);
+
+	ret = clk_prepare_enable(wdt->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to setup clock\n");
+		return ret;
+	}
+
+	/*
+	 * We use the clock rate to calculate the max timeout, so ensure it's
+	 * not zero to avoid a divide-by-zero exception.

drivers/watchdog/qcom-wdt.c line 123

Quoted 6 lines

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

+	 */
+	freq = clk_get_rate(wdt->clk);
+	if (freq == 0) {
+		dev_err(&pdev->dev, "invalid clock rate\n");
+		return -EINVAL;
+	}

This will need clk_disable_unprepare().

Since you are reading the frequency here, it might make sense to store it in struct qcom_wdt so you don't have to call clk_get_rate() again in the start function.

drivers/watchdog/qcom-wdt.c line 129

Quoted 5 lines

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

+	wdt->wdd.dev = &pdev->dev;
+	wdt->wdd.info = &qcom_wdt_info;
+	wdt->wdd.ops = &qcom_wdt_ops;
+	wdt->wdd.min_timeout = 1;
+	wdt->wdd.max_timeout = 0x10000000U / freq;

What if the frequency turns out to be larger than 8947848 Hz ? Then your maximum timeout is below the default timeout. And if the frequency is larger than 268435456 Hz, the maximum timeout would be 0.

drivers/watchdog/qcom-wdt.c line 136

Quoted 6 lines

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

+	/*
+	 * If 'timeout-sec' unspecified in devicetree, assume a 30 second
+	 * default.
+	 */
+	if (watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev))
+		wdt->wdd.timeout = 30;

You can just initialize timeout above with 30 seconds. Saves you the if statement here.

drivers/watchdog/qcom-wdt.c line 140

Quoted 3 lines

drivers/watchdog/qcom-wdt.c new file +3 -0

+	ret = watchdog_register_device(&wdt->wdd);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register watchdog\n");

This will need a clk_disable_unprepare().

Given that this is needed twice, you might want to consider using error exit code below, as suggested in CodingStyle.

+- clocks : shall contain the input clock phandle

Quoted 1 line · On Tuesday 23 September 2014 18:04:37 Josh Cartwright wrote:

+- clocks : shall contain the input clock phandle

Just nitpicking, but this is not just a phandle, it's a clock descriptor, which is a phandle followed by a set of arguments, which may be empty, depending the on the clock controller implementation.

I would just call it 'the input clock', rather than 'input clock phandle'.

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 | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

drivers/watchdog/qcom-wdt.c +2 -0

index d5e46e2..eba92ef 100644
@@ -16,6 +16,7 @@
 #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

@@ -25,6 +26,7 @@
 struct qcom_wdt {
 	struct watchdog_device	wdd;
 	struct clk		*clk;
+	struct notifier_block	restart_nb;
 	void __iomem		*base;
 };
 

@@ -86,6 +88,23 @@ static const struct watchdog_info qcom_wdt_info = {
 	.identity	= KBUILD_MODNAME,
 };

drivers/watchdog/qcom-wdt.c +12 -0

+	return NOTIFY_DONE;
+}
+
 static int qcom_wdt_probe(struct platform_device *pdev)
 {
 	struct qcom_wdt *wdt;

@@ -141,6 +160,14 @@ static int qcom_wdt_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	/*
+	 * 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;
 }

@@ -149,6 +176,7 @@ 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 · 7 lines

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

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