[PATCH 0/3] watchdog: add support for QCOM WDT

[PATCH 0/3] watchdog: add support for QCOM WDT

[Josh Cartwright]

This patchset provides support for the Watchdog Timer (WDT) found in the Krait
Processor Sub-system (KPSS) of the MSM8960, APQ8064, and IPQ8064 chips.

This driver is implemented ontop of WATCHDOG_CORE, and therefore its primary
interface is through userspace.  The implemantion is currently very basic (i.e.
it doesn't support PRETIMEOUT, even though it could be implemented through the
WDT's BARK functionality).  It should also be fairly easy to extend this driver
in the future to support newer chipsets as well.

Patch 3 also extends the driver to also register a restart_notifier, making it
possible for the WDT to act as a restart mechanism if more favorable mechanisms
don't work.  This is important for some boards which don't support PS_HOLD,
like the IPQ8064-based AP148 board.

Josh Cartwright (3):
  watchdog: qcom: add support for KPSS WDT
  watchdog: qcom: document device tree bindings
  watchdog: qcom: register a restart notifier

 .../devicetree/bindings/watchdog/qcom-wdt.txt      |  21 +++
 drivers/watchdog/Kconfig                           |  10 ++
 drivers/watchdog/Makefile                          |   1 +
 drivers/watchdog/qcom-wdt.c                        | 176 +++++++++++++++++++++
 4 files changed, 208 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/qcom-wdt.txt
 create mode 100644 drivers/watchdog/qcom-wdt.c

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

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

[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 <joshc@codeaurora.org>
---
 drivers/watchdog/Kconfig    |  10 +++
 drivers/watchdog/Makefile   |   1 +
 drivers/watchdog/qcom-wdt.c | 145 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 156 insertions(+)
 create mode 100644 drivers/watchdog/qcom-wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 1d1330a..5ccb963 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -443,6 +443,16 @@ config TEGRA_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called tegra_wdt.
 
+config QCOM_WDT
+	bool "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.
+
 # AVR32 Architecture
 
 config AT32AP700X_WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 468c320..d645448 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
 obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
 
diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
new file mode 100644
index 0000000..e9409f5
--- /dev/null
+++ b/drivers/watchdog/qcom-wdt.c
@@ -0,0 +1,145 @@
+/* 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/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;
+	unsigned long		freq;
+	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->freq, 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_watchdog_probe(struct platform_device *pdev)
+{
+	struct qcom_wdt *wdt;
+	struct resource *res;
+	u32 tmp;
+	int ret;
+
+	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, wdt);
+
+	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);
+
+	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency", &tmp);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to get clock-frequency\n");
+		return ret;
+	}
+
+	wdt->freq = tmp;
+
+	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->freq;
+	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");
+		return ret;
+	}
+
+	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_watchdog_probe,
+	.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");
-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

[PATCH 2/3] watchdog: qcom: document device tree bindings

[Josh Cartwright]

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 <joshc@codeaurora.org>
---
 .../devicetree/bindings/watchdog/qcom-wdt.txt       | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/qcom-wdt.txt

diff --git a/Documentation/devicetree/bindings/watchdog/qcom-wdt.txt b/Documentation/devicetree/bindings/watchdog/qcom-wdt.txt
new file mode 100644
index 0000000..e65cb8e
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/qcom-wdt.txt
@@ -0,0 +1,21 @@
+Qualcomm Krait Processor Sub-system (KPSS) Watchdog
+---------------------------------------------------
+
+Required properties :
+- compatible : shall contain only one of the following:
+
+			"qcom,kpss-wdt-msm8960"
+			"qcom,kpss-wdt-apq8064"
+			"qcom,kpss-wdt-ipq8064"
+
+- reg : shall contain base register location and length
+- clock-frequency : shall contain the frequency at which the watchdog ticks
+- timeout-sec : shall contain the default watchdog timeout in seconds
+
+Example:
+	watchdog@208a038 {
+		compatible = "qcom,kpss-wdt-ipq8064";
+		reg = <0x0208a038 0x40>;
+		clock-frequency = <32768>;
+		timeout-sec = <10>;
+	};
-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

[PATCH 3/3] watchdog: qcom: register a restart notifier

[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 <joshc@codeaurora.org>
---
 drivers/watchdog/qcom-wdt.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
index e9409f5..710ab43 100644
--- a/drivers/watchdog/qcom-wdt.c
+++ b/drivers/watchdog/qcom-wdt.c
@@ -15,6 +15,7 @@
 #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
@@ -24,6 +25,7 @@
 struct qcom_wdt {
 	struct watchdog_device	wdd;
 	unsigned long		freq;
+	struct notifier_block	restart_nb;
 	void __iomem		*base;
 };
 
@@ -82,6 +84,24 @@ 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);
+
+	/*
+	 * Trigger watchdog bite:
+	 *    Setup BITE_TIME to be very low, and enable WDT.
+	 */
+	mutex_lock(&wdt->wdd.lock);
+	writel_relaxed(0, wdt->base + WDT_EN);
+	writel_relaxed(1, wdt->base + WDT_RST);
+	writel_relaxed(0x31F3, wdt->base + WDT_BITE_TIME);
+	writel_relaxed(1, wdt->base + WDT_EN);
+	mutex_unlock(&wdt->wdd.lock);
+	return NOTIFY_DONE;
+}
+
 static int qcom_watchdog_probe(struct platform_device *pdev)
 {
 	struct qcom_wdt *wdt;
@@ -121,6 +141,17 @@ static int qcom_watchdog_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");
+		watchdog_unregister_device(&wdt->wdd);
+		return ret;
+	}
+
 	return 0;
 }
 
-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

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

[Guenter Roeck]

On 09/18/2014 03:26 PM, 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 <joshc@codeaurora.org>

Hi Josh,

comments inline.

Thanks,
Guenter

> ---
>   drivers/watchdog/Kconfig    |  10 +++
>   drivers/watchdog/Makefile   |   1 +
>   drivers/watchdog/qcom-wdt.c | 145 ++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 156 insertions(+)
>   create mode 100644 drivers/watchdog/qcom-wdt.c
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 1d1330a..5ccb963 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -443,6 +443,16 @@ config TEGRA_WATCHDOG
>   	  To compile this driver as a module, choose M here: the
>   	  module will be called tegra_wdt.
>
> +config QCOM_WDT
> +	bool "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.
> +
>   # AVR32 Architecture
>
>   config AT32AP700X_WDT
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 468c320..d645448 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
>   obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
>
> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> new file mode 100644
> index 0000000..e9409f5
> --- /dev/null
> +++ b/drivers/watchdog/qcom-wdt.c
> @@ -0,0 +1,145 @@
> +/* 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/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;
> +	unsigned long		freq;
> +	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->freq, 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_watchdog_probe(struct platform_device *pdev)
> +{
> +	struct qcom_wdt *wdt;
> +	struct resource *res;
> +	u32 tmp;
> +	int ret;
> +
> +	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
> +	if (!wdt)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, wdt);
> +
> +	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);
> +
> +	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency", &tmp);
> +	if (ret) {
> +		dev_err(&pdev->dev, "unable to get clock-frequency\n");
> +		return ret;
> +	}
> +

You might want to use a clock property here, and the complete sequence of
	devm_clk_get
	clk_prepare_enable
	clk_disable_unprepare
	clk_get_rate

> +	wdt->freq = tmp;
> +
> +	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->freq;

As written, wdt->freq can be 0, which results in a nice division by zero here.

> +	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);

That leaves you with no default timeout if timeout-sec is not set in devicetree,
which if I understand the code correctly might result in an immediate reset.
Is this really what you want to happen ?

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

No remove function ?

Yes, you don't need it, because the driver can only be built into the kernel,
but there is a practical impact: It means the driver must always be built
into the kernel even if the image is supposed to be used on different systems,
some of which may not support this specific watchdog.

Sure, you might say that you don't care about images supporting more than one
hardware, but the tendency seems to be multi-target images nowadays.

> +	.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");
>

Re: [PATCH 3/3] watchdog: qcom: register a restart notifier

[Guenter Roeck]

On 09/18/2014 03:27 PM, Josh Cartwright wrote:
> 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 <joshc@codeaurora.org>
> ---
>   drivers/watchdog/qcom-wdt.c | 31 +++++++++++++++++++++++++++++++
>   1 file changed, 31 insertions(+)
>
> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> index e9409f5..710ab43 100644
> --- a/drivers/watchdog/qcom-wdt.c
> +++ b/drivers/watchdog/qcom-wdt.c
> @@ -15,6 +15,7 @@
>   #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
> @@ -24,6 +25,7 @@
>   struct qcom_wdt {
>   	struct watchdog_device	wdd;
>   	unsigned long		freq;
> +	struct notifier_block	restart_nb;
>   	void __iomem		*base;
>   };
>
> @@ -82,6 +84,24 @@ 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);
> +
> +	/*
> +	 * Trigger watchdog bite:
> +	 *    Setup BITE_TIME to be very low, and enable WDT.
> +	 */
> +	mutex_lock(&wdt->wdd.lock);

At this time you don't need to worry about locks.

Actually, this might be dangerous if the lock happens to be taken,
as it won't be released (there is no other code running anymore
when this function is called).

> +	writel_relaxed(0, wdt->base + WDT_EN);
> +	writel_relaxed(1, wdt->base + WDT_RST);
> +	writel_relaxed(0x31F3, wdt->base + WDT_BITE_TIME);

What is the magic here, ie what does 0x31F3 stand for ?

> +	writel_relaxed(1, wdt->base + WDT_EN);
> +	mutex_unlock(&wdt->wdd.lock);
> +	return NOTIFY_DONE;
> +}
> +
>   static int qcom_watchdog_probe(struct platform_device *pdev)
>   {
>   	struct qcom_wdt *wdt;
> @@ -121,6 +141,17 @@ static int qcom_watchdog_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");
> +		watchdog_unregister_device(&wdt->wdd);
> +		return ret;

Sure you want to return an error here ? The watchdog itself is still working,
and this is supposed to be a restart method of last resort. Causing the driver
to fail loading because it can not register its restart handler seems to be
a bit aggressive.

Thanks,
Guenter

> +	}
> +
>   	return 0;
>   }
>
>

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

[Josh Cartwright]

On Thu, Sep 18, 2014 at 07:41:17PM -0700, Guenter Roeck wrote:
> On 09/18/2014 03:26 PM, 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 <joshc@codeaurora.org>
> 
> Hi Josh,
> 
> comments inline.

Thanks for taking a look!

[..]
> >+static int qcom_watchdog_probe(struct platform_device *pdev)
> >+{
> >+	struct qcom_wdt *wdt;
> >+	struct resource *res;
> >+	u32 tmp;
> >+	int ret;
> >+
> >+	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
> >+	if (!wdt)
> >+		return -ENOMEM;
> >+
> >+	platform_set_drvdata(pdev, wdt);
> >+
> >+	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);
> >+
> >+	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency", &tmp);
> >+	if (ret) {
> >+		dev_err(&pdev->dev, "unable to get clock-frequency\n");
> >+		return ret;
> >+	}
> >+
>
> You might want to use a clock property here, and the complete sequence of
> 	devm_clk_get
> 	clk_prepare_enable
> 	clk_disable_unprepare
> 	clk_get_rate

Agreed.  I think this would be ideal.  I'll need to take a closer look
at how this thing is clocked, and how/if the clocks are currently
being modelled.

> >+	wdt->freq = tmp;
> >+
> >+	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->freq;
>
> As written, wdt->freq can be 0, which results in a nice division by zero here.

Indeed.  I'll add a check.

> >+	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
>
> That leaves you with no default timeout if timeout-sec is not set in devicetree,
> which if I understand the code correctly might result in an immediate reset.
> Is this really what you want to happen ?

I think I'd like to handle timeout-sec being unspecified as an error at
probe.  If someone explicitly sets timeout-sec = <0>, then they get what
they ask for.  I'll take another look to see how to make this happen.

> >+
> >+	ret = watchdog_register_device(&wdt->wdd);
> >+	if (ret) {
> >+		dev_err(&pdev->dev, "failed to register watchdog\n");
> >+		return ret;
> >+	}
> >+
> >+	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_watchdog_probe,
>
> No remove function ?
>
> Yes, you don't need it, because the driver can only be built into the kernel,
> but there is a practical impact: It means the driver must always be built
> into the kernel even if the image is supposed to be used on different systems,
> some of which may not support this specific watchdog.
>
> Sure, you might say that you don't care about images supporting more than one
> hardware, but the tendency seems to be multi-target images nowadays.

This was motivated by the addition of the restart_handler bits in patch
3.  For some reason I was thinking there were race conditions between
module unloading/the restart_handler mechanism, but looking at it again,
I'm not so sure.  Is it safe to implement these handlers in modules?  If
so, I'll revisit this.

Thanks again,
  Josh

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

Re: [PATCH 3/3] watchdog: qcom: register a restart notifier

[Josh Cartwright]

On Thu, Sep 18, 2014 at 07:47:54PM -0700, Guenter Roeck wrote:
> On 09/18/2014 03:27 PM, Josh Cartwright wrote:
> >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 <joshc@codeaurora.org>
[..]
> >+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);
> >+
> >+	/*
> >+	 * Trigger watchdog bite:
> >+	 *    Setup BITE_TIME to be very low, and enable WDT.
> >+	 */
> >+	mutex_lock(&wdt->wdd.lock);
> 
> At this time you don't need to worry about locks.
> 
> Actually, this might be dangerous if the lock happens to be taken,
> as it won't be released (there is no other code running anymore
> when this function is called).

Ah, great.  I'll drop the locking.

> >+	writel_relaxed(0, wdt->base + WDT_EN);
> >+	writel_relaxed(1, wdt->base + WDT_RST);
> >+	writel_relaxed(0x31F3, wdt->base + WDT_BITE_TIME);
> 
> What is the magic here, ie what does 0x31F3 stand for ?

Nothing magic, it's just a reasonably low value to set the bite time
counter at.  It also happens to be the value at reset.

> >+	writel_relaxed(1, wdt->base + WDT_EN);
> >+	mutex_unlock(&wdt->wdd.lock);
> >+	return NOTIFY_DONE;
> >+}
> >+
> >  static int qcom_watchdog_probe(struct platform_device *pdev)
> >  {
> >  	struct qcom_wdt *wdt;
> >@@ -121,6 +141,17 @@ static int qcom_watchdog_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");
> >+		watchdog_unregister_device(&wdt->wdd);
> >+		return ret;
> 
> Sure you want to return an error here ? The watchdog itself is still working,
> and this is supposed to be a restart method of last resort. Causing the driver
> to fail loading because it can not register its restart handler seems to be
> a bit aggressive.

It is a bit aggressive.  I'll at least drop it to a dev_warn(); even
though it is a "last resort", on some boards it's the only available
mechanism for reliable restart.

Thanks!
  Josh

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

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

[Guenter Roeck]

On 09/18/2014 08:24 PM, Josh Cartwright wrote:
> On Thu, Sep 18, 2014 at 07:41:17PM -0700, Guenter Roeck wrote:
>> On 09/18/2014 03:26 PM, 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 <joshc@codeaurora.org>
>>
>> Hi Josh,
>>
>> comments inline.
>
> Thanks for taking a look!
>
> [..]
>>> +static int qcom_watchdog_probe(struct platform_device *pdev)
>>> +{
>>> +	struct qcom_wdt *wdt;
>>> +	struct resource *res;
>>> +	u32 tmp;
>>> +	int ret;
>>> +
>>> +	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
>>> +	if (!wdt)
>>> +		return -ENOMEM;
>>> +
>>> +	platform_set_drvdata(pdev, wdt);
>>> +
>>> +	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);
>>> +
>>> +	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency", &tmp);
>>> +	if (ret) {
>>> +		dev_err(&pdev->dev, "unable to get clock-frequency\n");
>>> +		return ret;
>>> +	}
>>> +
>>
>> You might want to use a clock property here, and the complete sequence of
>> 	devm_clk_get
>> 	clk_prepare_enable
>> 	clk_disable_unprepare
>> 	clk_get_rate
>
> Agreed.  I think this would be ideal.  I'll need to take a closer look
> at how this thing is clocked, and how/if the clocks are currently
> being modelled.
>

I think you should be able to specify some kind of "fixed" clock.
Other watchdog drivers use the mechanism; maybe you can find some examples.

>>> +	wdt->freq = tmp;
>>> +
>>> +	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->freq;
>>
>> As written, wdt->freq can be 0, which results in a nice division by zero here.
>
> Indeed.  I'll add a check.
>
>>> +	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
>>
>> That leaves you with no default timeout if timeout-sec is not set in devicetree,
>> which if I understand the code correctly might result in an immediate reset.
>> Is this really what you want to happen ?
>
> I think I'd like to handle timeout-sec being unspecified as an error at
> probe.  If someone explicitly sets timeout-sec = <0>, then they get what
> they ask for.  I'll take another look to see how to make this happen.
>

Hmm.. kind of unusual. Usual would be to initialize the timeout together
with min_timeout / max_timeout above and only force the user to specify
a value if the default timeout is not desirable. You don't really gain
anything by making timeout-sec mandatory.

>>> +
>>> +	ret = watchdog_register_device(&wdt->wdd);
>>> +	if (ret) {
>>> +		dev_err(&pdev->dev, "failed to register watchdog\n");
>>> +		return ret;
>>> +	}
>>> +
>>> +	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_watchdog_probe,
>>
>> No remove function ?
>>
>> Yes, you don't need it, because the driver can only be built into the kernel,
>> but there is a practical impact: It means the driver must always be built
>> into the kernel even if the image is supposed to be used on different systems,
>> some of which may not support this specific watchdog.
>>
>> Sure, you might say that you don't care about images supporting more than one
>> hardware, but the tendency seems to be multi-target images nowadays.
>
> This was motivated by the addition of the restart_handler bits in patch
> 3.  For some reason I was thinking there were race conditions between
> module unloading/the restart_handler mechanism, but looking at it again,
> I'm not so sure.  Is it safe to implement these handlers in modules?  If
> so, I'll revisit this.
>
Yes, it is safe. To ensure there are no race conditions was one of the reasons
for implementing the restart handler as notifier call chain.

Guenter

Re: [PATCH 3/3] watchdog: qcom: register a restart notifier

[Guenter Roeck]

On 09/18/2014 08:32 PM, Josh Cartwright wrote:
> On Thu, Sep 18, 2014 at 07:47:54PM -0700, Guenter Roeck wrote:
>> On 09/18/2014 03:27 PM, Josh Cartwright wrote:
>>> 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 <joshc@codeaurora.org>
> [..]
>>> +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);
>>> +
>>> +	/*
>>> +	 * Trigger watchdog bite:
>>> +	 *    Setup BITE_TIME to be very low, and enable WDT.
>>> +	 */
>>> +	mutex_lock(&wdt->wdd.lock);
>>
>> At this time you don't need to worry about locks.
>>
>> Actually, this might be dangerous if the lock happens to be taken,
>> as it won't be released (there is no other code running anymore
>> when this function is called).
>
> Ah, great.  I'll drop the locking.
>
>>> +	writel_relaxed(0, wdt->base + WDT_EN);
>>> +	writel_relaxed(1, wdt->base + WDT_RST);
>>> +	writel_relaxed(0x31F3, wdt->base + WDT_BITE_TIME);
>>
>> What is the magic here, ie what does 0x31F3 stand for ?
>
> Nothing magic, it's just a reasonably low value to set the bite time
> counter at.  It also happens to be the value at reset.
>
Can you add a note explaining that this reflects a reset delay of <n>
milliseconds or whatever it is ?

>>> +	writel_relaxed(1, wdt->base + WDT_EN);
>>> +	mutex_unlock(&wdt->wdd.lock);
>>> +	return NOTIFY_DONE;
>>> +}
>>> +
>>>   static int qcom_watchdog_probe(struct platform_device *pdev)
>>>   {
>>>   	struct qcom_wdt *wdt;
>>> @@ -121,6 +141,17 @@ static int qcom_watchdog_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");
>>> +		watchdog_unregister_device(&wdt->wdd);
>>> +		return ret;
>>
>> Sure you want to return an error here ? The watchdog itself is still working,
>> and this is supposed to be a restart method of last resort. Causing the driver
>> to fail loading because it can not register its restart handler seems to be
>> a bit aggressive.
>
> It is a bit aggressive.  I'll at least drop it to a dev_warn(); even
> though it is a "last resort", on some boards it's the only available
> mechanism for reliable restart.
>
Sure, but the problem is that you don't let people use the watchdog just
because restart handler registration failed. dev_err or dev_warn is fine,
my concern was not the message but that you abort watchdog registration
in this case.

Kind of letting people not use their car just because one of its lights
failed.

Guenter

Re: [PATCH 3/3] watchdog: qcom: register a restart notifier

[Pramod Gurav]

Hi Josh,

Tested this patch on IFC6410 by disabling pinctrl ps_hold reset
implementation and on top of Guenter's patchset for restart_notifier.

Tested-by: pramod.gurav@smartplayin.com

I picked up DT changes from bindings as they are from this patchset.

Thanks
Pramod
On Friday 19 September 2014 03:57 AM, Josh Cartwright wrote:
> 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 <joshc@codeaurora.org>
> ---
>  drivers/watchdog/qcom-wdt.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> index e9409f5..710ab43 100644
> --- a/drivers/watchdog/qcom-wdt.c
> +++ b/drivers/watchdog/qcom-wdt.c
> @@ -15,6 +15,7 @@
>  #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
> @@ -24,6 +25,7 @@
>  struct qcom_wdt {
>  	struct watchdog_device	wdd;
>  	unsigned long		freq;
> +	struct notifier_block	restart_nb;
>  	void __iomem		*base;
>  };
>  
> @@ -82,6 +84,24 @@ 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);
> +
> +	/*
> +	 * Trigger watchdog bite:
> +	 *    Setup BITE_TIME to be very low, and enable WDT.
> +	 */
> +	mutex_lock(&wdt->wdd.lock);
> +	writel_relaxed(0, wdt->base + WDT_EN);
> +	writel_relaxed(1, wdt->base + WDT_RST);
> +	writel_relaxed(0x31F3, wdt->base + WDT_BITE_TIME);
> +	writel_relaxed(1, wdt->base + WDT_EN);
> +	mutex_unlock(&wdt->wdd.lock);
> +	return NOTIFY_DONE;
> +}
> +
>  static int qcom_watchdog_probe(struct platform_device *pdev)
>  {
>  	struct qcom_wdt *wdt;
> @@ -121,6 +141,17 @@ static int qcom_watchdog_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");
> +		watchdog_unregister_device(&wdt->wdd);
> +		return ret;
> +	}
> +
>  	return 0;
>  }
>  
> 

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

[Josh Cartwright]

On Thu, Sep 18, 2014 at 08:41:43PM -0700, Guenter Roeck wrote:
> On 09/18/2014 08:24 PM, Josh Cartwright wrote:
> >On Thu, Sep 18, 2014 at 07:41:17PM -0700, Guenter Roeck wrote:
> >>On 09/18/2014 03:26 PM, 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 <joshc@codeaurora.org>
> >>
> >>Hi Josh,
> >>
> >>comments inline.
> >
> >Thanks for taking a look!
> >
[..]
> >>>+	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
> >>
> >>That leaves you with no default timeout if timeout-sec is not set in devicetree,
> >>which if I understand the code correctly might result in an immediate reset.
> >>Is this really what you want to happen ?
> >
> >I think I'd like to handle timeout-sec being unspecified as an error at
> >probe.  If someone explicitly sets timeout-sec = <0>, then they get what
> >they ask for.  I'll take another look to see how to make this happen.
> >
> 
> Hmm.. kind of unusual. Usual would be to initialize the timeout together
> with min_timeout / max_timeout above and only force the user to specify
> a value if the default timeout is not desirable. You don't really gain
> anything by making timeout-sec mandatory.

Making timeout-sec mandatory makes it so I don't have to decide what a
"sane default" is. :)

It's even less clear about what a sane default is looking at the other
watchdog drivers.  From the drivers I looked at, it ranges any where
from 30s to 2mins.  Am I just to choose?  Why do these even differ
between all of the drivers?

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

Re: [PATCH 3/3] watchdog: qcom: register a restart notifier

[Josh Cartwright]

On Thu, Sep 18, 2014 at 09:03:18PM -0700, Guenter Roeck wrote:
> On 09/18/2014 08:32 PM, Josh Cartwright wrote:
> >On Thu, Sep 18, 2014 at 07:47:54PM -0700, Guenter Roeck wrote:
> >>On 09/18/2014 03:27 PM, Josh Cartwright wrote:
[..]
> >
> >Nothing magic, it's just a reasonably low value to set the bite time
> >counter at.  It also happens to be the value at reset.
> >
> Can you add a note explaining that this reflects a reset delay of <n>
> milliseconds or whatever it is ?

Certainly.  Will do.

Thanks,
  Josh

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

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

[Guenter Roeck]

On Fri, Sep 19, 2014 at 11:25:50AM -0500, Josh Cartwright wrote:
> On Thu, Sep 18, 2014 at 08:41:43PM -0700, Guenter Roeck wrote:
> > On 09/18/2014 08:24 PM, Josh Cartwright wrote:
> > >On Thu, Sep 18, 2014 at 07:41:17PM -0700, Guenter Roeck wrote:
> > >>On 09/18/2014 03:26 PM, 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 <joshc@codeaurora.org>
> > >>
> > >>Hi Josh,
> > >>
> > >>comments inline.
> > >
> > >Thanks for taking a look!
> > >
> [..]
> > >>>+	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
> > >>
> > >>That leaves you with no default timeout if timeout-sec is not set in devicetree,
> > >>which if I understand the code correctly might result in an immediate reset.
> > >>Is this really what you want to happen ?
> > >
> > >I think I'd like to handle timeout-sec being unspecified as an error at
> > >probe.  If someone explicitly sets timeout-sec = <0>, then they get what
> > >they ask for.  I'll take another look to see how to make this happen.
> > >
> > 
> > Hmm.. kind of unusual. Usual would be to initialize the timeout together
> > with min_timeout / max_timeout above and only force the user to specify
> > a value if the default timeout is not desirable. You don't really gain
> > anything by making timeout-sec mandatory.
> 
> Making timeout-sec mandatory makes it so I don't have to decide what a
> "sane default" is. :)
> 
Bad excuse ;-). You just force others to make the decision for you.

> It's even less clear about what a sane default is looking at the other
> watchdog drivers.  From the drivers I looked at, it ranges any where
> from 30s to 2mins.  Am I just to choose?  Why do these even differ
> between all of the drivers?
> 
Sanity is defined as the majority opinion, as expressed quite nicely in
"Everyone is insane but me".

Just pick something in between. If you don't want to make a decision, pick
30 seconds and blame it on me.

Maybe someone at some point finds a common ground. Until then it is per driver.

Thanks,
Guenter