Re: [PATCH v2.1 1/2] watchdog: loongson1: Add Loongson1 SoC watchdog driver

[Yang Ling <gnaygnil@gmail.com>]

Hi Guenter,

On Fri, Oct 21, 2016 at 07:23:21AM -0700, Guenter Roeck wrote:
> On 10/20/2016 10:45 PM, Yang Ling wrote:
> >Add watchdog timer specific driver for Loongson1 SoC.
> >
> >Signed-off-by: Yang Ling <gnaygnil@gmail.com>
> >
> >---
> >V2.1 from Kelvin Cheung:
> >  Use max_hw_heartbeat_ms instead of max_timeout.
> >V2:
> >  Increase the value of the default heartbeat.
> >  Modify the setup process for register.
> >  Order include files and Makefile alphabetically.
> >V1.1:
> >  Add a little debugging information.
> >---
> > drivers/watchdog/Kconfig         |   7 ++
> > drivers/watchdog/Makefile        |   1 +
> > drivers/watchdog/loongson1_wdt.c | 158 +++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 166 insertions(+)
> > create mode 100644 drivers/watchdog/loongson1_wdt.c
> >
> >diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> >index 50dbaa8..6707d43 100644
> >--- a/drivers/watchdog/Kconfig
> >+++ b/drivers/watchdog/Kconfig
> >@@ -1513,6 +1513,13 @@ config LANTIQ_WDT
> > 	help
> > 	  Hardware driver for the Lantiq SoC Watchdog Timer.
> >
> >+config LOONGSON1_WDT
> >+	tristate "Loongson1 SoC hardware watchdog"
> >+	depends on MACH_LOONGSON32
> >+	select WATCHDOG_CORE
> >+	help
> >+	  Hardware driver for the Loongson1 SoC Watchdog Timer.
> >+
> > config RALINK_WDT
> > 	tristate "Ralink SoC watchdog"
> > 	select WATCHDOG_CORE
> >diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> >index cba0043..b6a8d70 100644
> >--- a/drivers/watchdog/Makefile
> >+++ b/drivers/watchdog/Makefile
> >@@ -157,6 +157,7 @@ obj-$(CONFIG_TXX9_WDT) += txx9wdt.o
> > obj-$(CONFIG_OCTEON_WDT) += octeon-wdt.o
> > octeon-wdt-y := octeon-wdt-main.o octeon-wdt-nmi.o
> > obj-$(CONFIG_LANTIQ_WDT) += lantiq_wdt.o
> >+obj-$(CONFIG_LOONGSON1_WDT) += loongson1_wdt.o
> > obj-$(CONFIG_RALINK_WDT) += rt2880_wdt.o
> > obj-$(CONFIG_IMGPDC_WDT) += imgpdc_wdt.o
> > obj-$(CONFIG_MT7621_WDT) += mt7621_wdt.o
> >diff --git a/drivers/watchdog/loongson1_wdt.c b/drivers/watchdog/loongson1_wdt.c
> >new file mode 100644
> >index 0000000..f885294
> >--- /dev/null
> >+++ b/drivers/watchdog/loongson1_wdt.c
> >@@ -0,0 +1,158 @@
> >+/*
> >+ * 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.
> 
> Odd spacing.

Remove these wide character in the next release.

> 
> >+ */
> >+
> >+#include <linux/clk.h>
> >+#include <linux/module.h>
> >+#include <linux/platform_device.h>
> >+#include <linux/watchdog.h>
> >+#include <loongson1.h>
> >+
> >+#define DEFAULT_HEARTBEAT	30
> >+
> >+static bool nowayout = WATCHDOG_NOWAYOUT;
> >+module_param(nowayout, bool, 0444);
> >+
> >+static unsigned int heartbeat = DEFAULT_HEARTBEAT;
> >+module_param(heartbeat, uint, 0444);
> >+
> >+struct ls1x_wdt_drvdata {
> >+	void __iomem *base;
> >+	struct clk *clk;
> >+	unsigned int counts_per_second;
> >+	struct watchdog_device wdt;
> >+};
> >+
> >+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_SET);
> >+
> >+	return 0;
> >+}
> >+
> >+static int ls1x_wdt_set_timeout(struct watchdog_device *wdt_dev,
> >+				unsigned int timeout)
> >+{
> >+	struct ls1x_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> >+	unsigned int counts;
> >+
> >+	wdt_dev->timeout = min(timeout, wdt_dev->max_hw_heartbeat_ms / 1000);
> 
> The point of using max_hw_heartbeat_ms is that the watchdog core takes care of
> timeouts larger than the maximum supported by the hardware. What you should do
> here is something along the line of
> 
> 	wdt_dev->timeout = timeout;
> 	counts = drvdata->counts_per_second * min(timeout, wdt_dev->max_hw_heartbeat_ms / 1000);

This will be changed in the next release.

> 
> >+	counts = drvdata->counts_per_second * wdt_dev->timeout;
> >+
> >+	writel(counts, drvdata->base + WDT_TIMER);
> >+
> >+	return 0;
> >+}
> >+
> >+static int ls1x_wdt_start(struct watchdog_device *wdt_dev)
> >+{
> >+	struct ls1x_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> >+
> >+	writel(0x1, drvdata->base + WDT_EN);
> >+
> >+	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);
> >+
> >+	drvdata->counts_per_second = clk_get_rate(drvdata->clk);
> 
> clk_get_rate() can at least in theory return 0,

Check the return value in the next release.

> 
> >+
> >+	ls1x_wdt = &drvdata->wdt;
> >+	ls1x_wdt->info = &ls1x_wdt_info;
> >+	ls1x_wdt->ops = &ls1x_wdt_ops;
> >+	ls1x_wdt->min_timeout = 1;
> >+	ls1x_wdt->max_hw_heartbeat_ms = U32_MAX / drvdata->counts_per_second *
> >+					1000;
> 
> which would result in a crash here.
> 
> >+	ls1x_wdt->parent = &pdev->dev;
> >+
> >+	watchdog_init_timeout(ls1x_wdt, heartbeat, &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);
> 
> This should not be necessary. If the watchdog device is open (meaning the
> watchdog may be running), you should not be able to unload the driver.
> Can you test ?

Remove it in the next release.

> 
> >+	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");
> >
> 

Thanks for your friendly reminder.