RE: [PATCH V3 2/4] watchdog: Add i.MX7ULP watchdog support

[Anson Huang]

Hi, Guenter

> On Tue, Aug 20, 2019 at 10:07:56PM -0400, Anson Huang wrote:
> > The i.MX7ULP Watchdog Timer (WDOG) module is an independent timer
> that
> > is available for system use.
> > It provides a safety feature to ensure that software is executing as
> > planned and that the CPU is not stuck in an infinite loop or executing
> > unintended code. If the WDOG module is not serviced
> > (refreshed) within a certain period, it resets the MCU.
> >
> > Add driver support for i.MX7ULP watchdog.
> >
> > Signed-off-by: Anson Huang <Anson.Huang@xxxxxxx>
> > ---
> > Changes since V2:
> > 	- add devm_add_action_or_reset to disable clk for remove action.
> > ---
> >  drivers/watchdog/Kconfig       |  13 +++
> >  drivers/watchdog/Makefile      |   1 +
> >  drivers/watchdog/imx7ulp_wdt.c | 246
> > +++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 260 insertions(+)
> >  create mode 100644 drivers/watchdog/imx7ulp_wdt.c
> >
> > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig index
> > a8f5c81..d68e5b5 100644
> > --- a/drivers/watchdog/Kconfig
> > +++ b/drivers/watchdog/Kconfig
> > @@ -724,6 +724,19 @@ config IMX_SC_WDT
> >  	  To compile this driver as a module, choose M here: the
> >  	  module will be called imx_sc_wdt.
> >
> > +config IMX7ULP_WDT
> > +	tristate "IMX7ULP Watchdog"
> > +	depends on ARCH_MXC || COMPILE_TEST
> > +	select WATCHDOG_CORE
> > +	help
> > +	  This is the driver for the hardware watchdog on the Freescale
> > +	  IMX7ULP and later processors. If you have one of these
> > +	  processors and wish to have watchdog support enabled,
> > +	  say Y, otherwise say N.
> > +
> > +	  To compile this driver as a module, choose M here: the
> > +	  module will be called imx7ulp_wdt.
> > +
> >  config UX500_WATCHDOG
> >  	tristate "ST-Ericsson Ux500 watchdog"
> >  	depends on MFD_DB8500_PRCMU
> > diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> > index b5a0aed..2ee352b 100644
> > --- a/drivers/watchdog/Makefile
> > +++ b/drivers/watchdog/Makefile
> > @@ -67,6 +67,7 @@ obj-$(CONFIG_TS4800_WATCHDOG) += ts4800_wdt.o
> >  obj-$(CONFIG_TS72XX_WATCHDOG) += ts72xx_wdt.o
> >  obj-$(CONFIG_IMX2_WDT) += imx2_wdt.o
> >  obj-$(CONFIG_IMX_SC_WDT) += imx_sc_wdt.o
> > +obj-$(CONFIG_IMX7ULP_WDT) += imx7ulp_wdt.o
> >  obj-$(CONFIG_UX500_WATCHDOG) += ux500_wdt.o
> >  obj-$(CONFIG_RETU_WATCHDOG) += retu_wdt.o
> >  obj-$(CONFIG_BCM2835_WDT) += bcm2835_wdt.o diff --git
> > a/drivers/watchdog/imx7ulp_wdt.c b/drivers/watchdog/imx7ulp_wdt.c
> new
> > file mode 100644 index 0000000..5d37957
> > --- /dev/null
> > +++ b/drivers/watchdog/imx7ulp_wdt.c
> > @@ -0,0 +1,246 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright 2019 NXP.
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/init.h>
> > +#include <linux/io.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/reboot.h>
> > +#include <linux/watchdog.h>
> > +
> > +#define WDOG_CS			0x0
> > +#define WDOG_CS_CMD32EN		BIT(13)
> > +#define WDOG_CS_ULK		BIT(11)
> > +#define WDOG_CS_RCS		BIT(10)
> > +#define WDOG_CS_EN		BIT(7)
> > +#define WDOG_CS_UPDATE		BIT(5)
> > +
> > +#define WDOG_CNT	0x4
> > +#define WDOG_TOVAL	0x8
> > +
> > +#define REFRESH_SEQ0	0xA602
> > +#define REFRESH_SEQ1	0xB480
> > +#define REFRESH		((REFRESH_SEQ1 << 16) | REFRESH_SEQ0)
> > +
> > +#define UNLOCK_SEQ0	0xC520
> > +#define UNLOCK_SEQ1	0xD928
> > +#define UNLOCK		((UNLOCK_SEQ1 << 16) | UNLOCK_SEQ0)
> > +
> > +#define DEFAULT_TIMEOUT	60
> > +#define MAX_TIMEOUT	128
> > +
> > +static bool nowayout = WATCHDOG_NOWAYOUT;
> module_param(nowayout,
> > +bool, 0000); MODULE_PARM_DESC(nowayout, "Watchdog cannot be
> stopped
> > +once started (default="
> > +		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> > +
> > +struct imx7ulp_wdt_device {
> > +	struct notifier_block restart_handler;
> > +	struct watchdog_device wdd;
> > +	void __iomem *base;
> > +	struct clk *clk;
> > +	int rate;
> > +};
> > +
> > +static inline void imx7ulp_wdt_enable(void __iomem *base, bool
> > +enable) {
> > +	u32 val = readl(base + WDOG_CS);
> > +
> > +	writel(UNLOCK, base + WDOG_CNT);
> > +	if (enable)
> > +		writel(val | WDOG_CS_EN, base + WDOG_CS);
> > +	else
> > +		writel(val & ~WDOG_CS_EN, base + WDOG_CS); }
> > +
> > +static inline bool imx7ulp_wdt_is_enabled(void __iomem *base) {
> > +	u32 val = readl(base + WDOG_CS);
> > +
> > +	return val & WDOG_CS_EN;
> > +}
> > +
> > +static int imx7ulp_wdt_ping(struct watchdog_device *wdog) {
> > +	struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
> > +
> > +	writel(REFRESH, wdt->base + WDOG_CNT);
> > +
> > +	return 0;
> > +}
> > +
> > +static int imx7ulp_wdt_start(struct watchdog_device *wdog) {
> > +	struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
> > +
> > +	imx7ulp_wdt_enable(wdt->base, true);
> > +
> > +	return 0;
> > +}
> > +
> > +static int imx7ulp_wdt_stop(struct watchdog_device *wdog) {
> > +	struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
> > +
> > +	imx7ulp_wdt_enable(wdt->base, false);
> > +
> > +	return 0;
> > +}
> > +
> > +static int imx7ulp_wdt_set_timeout(struct watchdog_device *wdog,
> > +				   unsigned int timeout)
> > +{
> > +	struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
> > +	u32 val = wdt->rate * timeout;
> > +
> > +	writel(UNLOCK, wdt->base + WDOG_CNT);
> > +	writel(val, wdt->base + WDOG_TOVAL);
> > +
> > +	wdog->timeout = timeout;
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct watchdog_ops imx7ulp_wdt_ops = {
> > +	.owner = THIS_MODULE,
> > +	.start = imx7ulp_wdt_start,
> > +	.stop  = imx7ulp_wdt_stop,
> > +	.ping  = imx7ulp_wdt_ping,
> > +	.set_timeout = imx7ulp_wdt_set_timeout, };
> > +
> > +static const struct watchdog_info imx7ulp_wdt_info = {
> > +	.identity = "i.MX7ULP watchdog timer",
> > +	.options  = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
> > +		    WDIOF_MAGICCLOSE,
> > +};
> > +
> > +static inline void imx7ulp_wdt_init(void __iomem *base, unsigned int
> > +timeout) {
> > +	u32 val;
> > +
> > +	/* unlock the wdog for reconfiguration */
> > +	writel_relaxed(UNLOCK_SEQ0, base + WDOG_CNT);
> > +	writel_relaxed(UNLOCK_SEQ1, base + WDOG_CNT);
> > +
> > +	/* set an initial timeout value in TOVAL */
> > +	writel(timeout, base + WDOG_TOVAL);
> > +	/* enable 32bit command sequence and reconfigure */
> > +	val = BIT(13) | BIT(8) | BIT(5);
> > +	writel(val, base + WDOG_CS);
> > +}
> > +
> > +static void imx7ulp_wdt_action(void *data) {
> > +	struct imx7ulp_wdt_device *imx7ulp_wdt = data;
> > +
> > +	clk_disable_unprepare(imx7ulp_wdt->clk);
> 
> If you had passed imx7ulp_wdt->clk as parameter, the dereference here
> would not be necessary.

Yup, I thought we may need other data later, so I just passed whole structure.
I agree with your idea, for now, we ONLY need the clk, so I will ONLY pass the clk
to save the dereference operation. Will send out V4.

> 
> > +}
> > +
> > +static int imx7ulp_wdt_probe(struct platform_device *pdev) {
> > +	struct imx7ulp_wdt_device *imx7ulp_wdt;
> > +	struct device *dev = &pdev->dev;
> > +	struct watchdog_device *wdog;
> > +	int ret;
> > +
> > +	imx7ulp_wdt = devm_kzalloc(dev, sizeof(*imx7ulp_wdt),
> GFP_KERNEL);
> > +	if (!imx7ulp_wdt)
> > +		return -ENOMEM;
> > +
> > +	platform_set_drvdata(pdev, imx7ulp_wdt);
> > +
> > +	imx7ulp_wdt->base = devm_platform_ioremap_resource(pdev, 0);
> > +	if (IS_ERR(imx7ulp_wdt->base))
> > +		return PTR_ERR(imx7ulp_wdt->base);
> > +
> > +	imx7ulp_wdt->clk = devm_clk_get(dev, NULL);
> > +	if (IS_ERR(imx7ulp_wdt->clk)) {
> > +		dev_err(dev, "Failed to get watchdog clock\n");
> > +		return PTR_ERR(imx7ulp_wdt->clk);
> > +	}
> > +
> > +	ret = clk_prepare_enable(imx7ulp_wdt->clk);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = devm_add_action_or_reset(dev, imx7ulp_wdt_action,
> imx7ulp_wdt);
> > +	if (ret)
> > +		return ret;
> > +
> > +	imx7ulp_wdt->rate = 1000;
> 
> I forgot to ask (sorry, I had noticed, but I guess I forgot).
> 
> Why not clk_get_rate() ? If the clock rate is fixed, why bother with a 'rate'
> variable ? You could use a constant instead whereever it is used.

OK, the clock rate is fixed on 7ULP, I will use a constant instead of the variable.

Thanks,
Anson

> 
> Thanks
> Guenter
> 
> > +	wdog = &imx7ulp_wdt->wdd;
> > +	wdog->info = &imx7ulp_wdt_info;
> > +	wdog->ops = &imx7ulp_wdt_ops;
> > +	wdog->min_timeout = 1;
> > +	wdog->max_timeout = MAX_TIMEOUT;
> > +	wdog->parent = dev;
> > +	wdog->timeout = DEFAULT_TIMEOUT;
> > +
> > +	watchdog_init_timeout(wdog, 0, dev);
> > +	watchdog_stop_on_reboot(wdog);
> > +	watchdog_stop_on_unregister(wdog);
> > +	watchdog_set_drvdata(wdog, imx7ulp_wdt);
> > +	imx7ulp_wdt_init(imx7ulp_wdt->base, wdog->timeout *
> > +imx7ulp_wdt->rate);
> > +
> > +	return devm_watchdog_register_device(dev, wdog); }
> > +
> > +static int __maybe_unused imx7ulp_wdt_suspend(struct device *dev) {
> > +	struct imx7ulp_wdt_device *imx7ulp_wdt = dev_get_drvdata(dev);
> > +
> > +	if (watchdog_active(&imx7ulp_wdt->wdd))
> > +		imx7ulp_wdt_stop(&imx7ulp_wdt->wdd);
> > +
> > +	clk_disable_unprepare(imx7ulp_wdt->clk);
> > +
> > +	return 0;
> > +}
> > +
> > +static int __maybe_unused imx7ulp_wdt_resume(struct device *dev) {
> > +	struct imx7ulp_wdt_device *imx7ulp_wdt = dev_get_drvdata(dev);
> > +	u32 timeout = imx7ulp_wdt->wdd.timeout * imx7ulp_wdt->rate;
> > +	int ret;
> > +
> > +	ret = clk_prepare_enable(imx7ulp_wdt->clk);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (imx7ulp_wdt_is_enabled(imx7ulp_wdt->base))
> > +		imx7ulp_wdt_init(imx7ulp_wdt->base, timeout);
> > +
> > +	if (watchdog_active(&imx7ulp_wdt->wdd))
> > +		imx7ulp_wdt_start(&imx7ulp_wdt->wdd);
> > +
> > +	return 0;
> > +}
> > +
> > +static SIMPLE_DEV_PM_OPS(imx7ulp_wdt_pm_ops,
> imx7ulp_wdt_suspend,
> > +			 imx7ulp_wdt_resume);
> > +
> > +static const struct of_device_id imx7ulp_wdt_dt_ids[] = {
> > +	{ .compatible = "fsl,imx7ulp-wdt", },
> > +	{ /* sentinel */ }
> > +};
> > +MODULE_DEVICE_TABLE(of, imx7ulp_wdt_dt_ids);
> > +
> > +static struct platform_driver imx7ulp_wdt_driver = {
> > +	.probe		= imx7ulp_wdt_probe,
> > +	.driver		= {
> > +		.name	= "imx7ulp-wdt",
> > +		.pm	= &imx7ulp_wdt_pm_ops,
> > +		.of_match_table = imx7ulp_wdt_dt_ids,
> > +	},
> > +};
> > +module_platform_driver(imx7ulp_wdt_driver);
> > +
> > +MODULE_AUTHOR("Anson Huang <Anson.Huang@xxxxxxx>");
> > +MODULE_DESCRIPTION("Freescale i.MX7ULP watchdog driver");
> > +MODULE_LICENSE("GPL v2");
> > --
> > 2.7.4
> >