Re: [PATCH v1.1 1/2] watchdog: loongson1: Add Loongson1 SoC watchdog driver

[Yang Ling <gnaygnil@gmail.com>]

On Tue, Oct 11, 2016 at 07:54:03AM -0700, Guenter Roeck wrote:
> On 10/11/2016 07:10 AM, Yang Ling wrote:
> >Add watchdog timer specific driver for Loongson1 SoC.
> >
> >Signed-off-by: Yang Ling <gnaygnil@gmail.com>
> >
> >---
> >V1.1:
> > Add a little debugging information.
> >---
> > drivers/watchdog/Kconfig         |   7 ++
> > drivers/watchdog/Makefile        |   1 +
> > drivers/watchdog/loongson1_wdt.c | 160 +++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 168 insertions(+)
> > create mode 100644 drivers/watchdog/loongson1_wdt.c
> >
> >diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> >index 50dbaa8..28c44f2 100644
> >--- a/drivers/watchdog/Kconfig
> >+++ b/drivers/watchdog/Kconfig
> >@@ -1553,6 +1553,13 @@ config PIC32_DMT
> > 	  To compile this driver as a loadable module, choose M here.
> > 	  The module will be called pic32-dmt.
> >
> >+config LOONGSON1_WDT
> >+	tristate "Loongson1 SoC hardware watchdog"
> >+	depends on MACH_LOONGSON32
> >+	select WATCHDOG_CORE
> >+	help
> >+	  Hardware driver for the Loongson1 SoC Watchdog Timer.
> >+
> > # PARISC Architecture
> >
> > # POWERPC Architecture
> >diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> >index cba0043..bd3b00e 100644
> >--- a/drivers/watchdog/Makefile
> >+++ b/drivers/watchdog/Makefile
> >@@ -162,6 +162,7 @@ obj-$(CONFIG_IMGPDC_WDT) += imgpdc_wdt.o
> > obj-$(CONFIG_MT7621_WDT) += mt7621_wdt.o
> > obj-$(CONFIG_PIC32_WDT) += pic32-wdt.o
> > obj-$(CONFIG_PIC32_DMT) += pic32-dmt.o
> >+obj-$(CONFIG_LOONGSON1_WDT) += loongson1_wdt.o
> >
> > # PARISC Architecture
> >
> >diff --git a/drivers/watchdog/loongson1_wdt.c b/drivers/watchdog/loongson1_wdt.c
> >new file mode 100644
> >index 0000000..77b11f9
> >--- /dev/null
> >+++ b/drivers/watchdog/loongson1_wdt.c
> >@@ -0,0 +1,160 @@
> >+/*
> >+ * Copyright (c) 2016 Yang Ling <gnaygnil@gmail.com>
> >+ *
> >+ * This program is free software; you can redistribute	it and/or modify it
> >+ * under  the terms of	the GNU General	 Public License as published by the
> >+ * Free Software Foundation;  either version 2 of the  License, or (at your
> >+ * option) any later version.
> >+ */
> >+
> >+#include <linux/module.h>
> >+#include <linux/watchdog.h>
> >+#include <linux/platform_device.h>
> >+#include <linux/clk.h>
> >+
> >+#include <loongson1.h>
> >+
> >+#define MIN_HEARTBEAT		1
> >+#define MAX_HEARTBEAT		30
> >+#define DEFAULT_HEARTBEAT	10
> >+
> 
> The limits are pretty low. On many systems such low limits may result
> in boot failures if the watchdog is already running at boot.
> 
> It might make more sense to determine the maximum timeout dynamically based
> on the clock rate, and possibly use max_hw_heartbeat_ms instead of max_timeout
> to let the infrastructure handle small maximum timeouts.
> 
> Also, if it is possible that the watchdog is already running at boot, it might
> be desirable to detect this situation and inform the infrastructure about it
> (see WDOG_HW_RUNNING flag).
> 
> >+static bool nowayout = WATCHDOG_NOWAYOUT;
> >+module_param(nowayout, bool, 0);
> >+
> >+static unsigned int heartbeat = DEFAULT_HEARTBEAT;
> >+module_param(heartbeat, uint, 0);
> >+
> >+struct ls1x_wdt_drvdata {
> >+	struct watchdog_device wdt;
> >+	void __iomem *base;
> >+	unsigned int count;
> >+	struct clk *clk;
> >+};
> >+
> >+static int ls1x_wdt_ping(struct watchdog_device *wdt_dev)
> >+{
> >+	struct ls1x_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> >+
> >+	writel(0x1, drvdata->base + WDT_EN);
> 
> Does this enable the timeout ? If so, does it always have to be called ?
> And is it a good idea to call it prior to setting the counter ?
> 
> >+	writel(drvdata->count, drvdata->base + WDT_TIMER);
> 
> Is this needed for each ping ?
> 
> >+	writel(0x1, drvdata->base + WDT_SET);
> >+
> Or is this the actual ping ?
> 
> >+	return 0;
> >+}
> >+
> >+static int ls1x_wdt_set_timeout(struct watchdog_device *wdt_dev,
> >+				unsigned int new_timeout)
> >+{
> >+	struct ls1x_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> >+	int counts_per_second;
> >+
> >+	if (watchdog_init_timeout(wdt_dev, new_timeout, NULL))
> >+		return -EINVAL;
> 
> This is supposed to be called from the init function. The set_timeout
> is supposed to set the timeout, not to call back the infrastructure.
> 
> >+
> >+	counts_per_second = clk_get_rate(drvdata->clk);
> 
> clk_get_rate() can, at least in theory, return 0.
> In general it is better to call it once in the probe function,
> validate it, and store the value in the local data structure.
> 
> >+	drvdata->count = counts_per_second * wdt_dev->timeout;
> >+
> >+	ls1x_wdt_ping(wdt_dev);
> 
> No. This function can be called with the watchdog stopped.
> The infrastructure will call the ping function if needed.
> 
> >+
> >+	return 0;
> >+}
> >+
> >+static int ls1x_wdt_start(struct watchdog_device *wdt_dev)
> >+{
> >+	ls1x_wdt_set_timeout(wdt_dev, wdt_dev->timeout);
> 
> This function is supposed to start the watchdog, not to set the timeout.
> 
> >+
> >+	return 0;
> >+}
> >+
> >+static int ls1x_wdt_stop(struct watchdog_device *wdt_dev)
> >+{
> >+	struct ls1x_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> >+
> >+	writel(0x0, drvdata->base + WDT_EN);
> >+
> >+	return 0;
> >+}
> >+
> >+static const struct watchdog_info ls1x_wdt_info = {
> >+	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
> >+	.identity = "Loongson1 Watchdog",
> >+};
> >+
> >+static const struct watchdog_ops ls1x_wdt_ops = {
> >+	.owner = THIS_MODULE,
> >+	.start = ls1x_wdt_start,
> >+	.stop = ls1x_wdt_stop,
> >+	.ping = ls1x_wdt_ping,
> >+	.set_timeout = ls1x_wdt_set_timeout,
> >+};
> >+
> >+static int ls1x_wdt_probe(struct platform_device *pdev)
> >+{
> >+	struct ls1x_wdt_drvdata *drvdata;
> >+	struct watchdog_device *ls1x_wdt;
> >+	struct resource *res;
> >+	int ret;
> >+
> >+	drvdata = devm_kzalloc(&pdev->dev, sizeof(*drvdata), GFP_KERNEL);
> >+	if (!drvdata)
> >+		return -ENOMEM;
> >+
> >+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >+	drvdata->base = devm_ioremap_resource(&pdev->dev, res);
> >+	if (IS_ERR(drvdata->base))
> >+		return PTR_ERR(drvdata->base);
> >+
> >+	drvdata->clk = devm_clk_get(&pdev->dev, pdev->name);
> >+	if (IS_ERR(drvdata->clk)) {
> >+		dev_err(&pdev->dev, "failed to get %s clock\n", pdev->name);
> >+		return PTR_ERR(drvdata->clk);
> >+	}
> >+	clk_prepare_enable(drvdata->clk);
> >+
> >+	ls1x_wdt = &drvdata->wdt;
> >+	ls1x_wdt->info = &ls1x_wdt_info;
> >+	ls1x_wdt->ops = &ls1x_wdt_ops;
> >+	ls1x_wdt->timeout = heartbeat;
> >+	ls1x_wdt->min_timeout = MIN_HEARTBEAT;
> >+	ls1x_wdt->max_timeout = MAX_HEARTBEAT;
> >+	ls1x_wdt->parent = &pdev->dev;
> >+	watchdog_set_nowayout(ls1x_wdt, nowayout);
> >+	watchdog_set_drvdata(ls1x_wdt, drvdata);
> >+
> >+	ret = watchdog_register_device(&drvdata->wdt);
> >+	if (ret < 0) {
> >+		dev_err(&pdev->dev, "failed to register watchdog device\n");
> >+		return ret;
> >+	}
> >+
> >+	platform_set_drvdata(pdev, drvdata);
> >+
> >+	dev_info(&pdev->dev, "Loongson1 Watchdog driver registered\n");
> >+
> >+	return 0;
> >+}
> >+
> >+static int ls1x_wdt_remove(struct platform_device *pdev)
> >+{
> >+	struct ls1x_wdt_drvdata *drvdata = platform_get_drvdata(pdev);
> >+
> >+	ls1x_wdt_stop(&drvdata->wdt);
> >+	watchdog_unregister_device(&drvdata->wdt);
> >+	clk_disable_unprepare(drvdata->clk);
> >+
> >+	return 0;
> >+}
> >+
> >+static struct platform_driver ls1x_wdt_driver = {
> >+	.probe = ls1x_wdt_probe,
> >+	.remove = ls1x_wdt_remove,
> >+	.driver = {
> >+		.name = "ls1x-wdt",
> >+	},
> >+};
> >+
> >+module_platform_driver(ls1x_wdt_driver);
> >+
> >+MODULE_AUTHOR("Yang Ling <gnaygnil@gmail.com>");
> >+MODULE_DESCRIPTION("Loongson1 Watchdog Driver");
> >+MODULE_LICENSE("GPL");
> >
> 

I will improve these places in the next version.

Thanks for your friendly reminder.