[PATCH v3 1/3] watchdog: qcom: add support for KPSS WDT

From: linux@roeck-us.net (Guenter Roeck)
Date: 2014-09-25 18:39:08
Also in: linux-arm-msm, linux-devicetree, linux-watchdog, lkml

On Thu, Sep 25, 2014 at 12:48:51PM -0500, Josh Cartwright wrote:

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 <redacted>

Hi Josh,

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

Thanks,
Guenter

quoted hunk ↗ jump to hunk

---
 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

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 79d2589..c389ed7 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig

@@ -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

diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 985a66c..cede21e 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile

@@ -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

diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
new file mode 100644
index 0000000..0f56ca3
--- /dev/null
+++ b/drivers/watchdog/qcom-wdt.c

@@ -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;
+
+	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.

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

Same here.

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

and here.

+	}
+
+	/*
+	 * 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;
+	wdt->wdd.ops = &qcom_wdt_ops;
+	wdt->wdd.min_timeout = 1;
+	wdt->wdd.max_timeout = 0x10000000U / wdt->rate;
+
+	/*
+	 * If 'timeout-sec' unspecified in devicetree, assume a 30 second
+	 * default, unless the max timeout is less than 30 seconds, then use
+	 * the max instead.
+	 */
+	wdt->wdd.timeout = min(wdt->wdd.max_timeout, 30U);

Good idea.

+	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");
-- 
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