Date:   Tue, 12 Sep 2017 14:17:21 +0800
From:   Eric Long <eric.long@...eadtrum.com>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     Wim Van Sebroeck <wim@...ana.be>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "baolin.wang@...aro.org" <baolin.wang@...aro.org>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] watchdog: Add Spreadtrum watchdog driver

On Sat, Sep 09, 2017 at 03:32:48AM +0000, Guenter Roeck wrote:
> On 09/05/2017 10:38 PM, Eric Long wrote:
> > This patch adds the watchdog driver for Spreadtrum SC9860 platform.
> > 
> > Signed-off-by: Eric Long <eric.long@...eadtrum.com>
> > ---
> >   drivers/watchdog/Kconfig    |   8 +
> >   drivers/watchdog/Makefile   |   1 +
> >   drivers/watchdog/sprd_wdt.c | 366 ++++++++++++++++++++++++++++++++++++++++++++
> >   3 files changed, 375 insertions(+)
> >   create mode 100644 drivers/watchdog/sprd_wdt.c
> > 
> > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> > index c722cbf..ea07718 100644
> > --- a/drivers/watchdog/Kconfig
> > +++ b/drivers/watchdog/Kconfig
> > @@ -787,6 +787,14 @@ config UNIPHIER_WATCHDOG
> >   	  To compile this driver as a module, choose M here: the
> >   	  module will be called uniphier_wdt.
> >   
> > +config SPRD_WATCHDOG
> > +	tristate "Spreadtrum watchdog support"
> > +	depends on ARCH_SPRD
> > +	select WATCHDOG_CORE
> > +	help
> > +	  Say Y here to include support watchdog timer embedded
> > +	  into the Spreadtrum system.
> > +
> >   # AVR32 Architecture
> >   
> >   config AT32AP700X_WDT
> > diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> > index 56adf9f..187cca2 100644
> > --- a/drivers/watchdog/Makefile
> > +++ b/drivers/watchdog/Makefile
> > @@ -87,6 +87,7 @@ obj-$(CONFIG_ASPEED_WATCHDOG) += aspeed_wdt.o
> >   obj-$(CONFIG_ZX2967_WATCHDOG) += zx2967_wdt.o
> >   obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
> >   obj-$(CONFIG_UNIPHIER_WATCHDOG) += uniphier_wdt.o
> > +obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
> >   
> >   # AVR32 Architecture
> >   obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
> > diff --git a/drivers/watchdog/sprd_wdt.c b/drivers/watchdog/sprd_wdt.c
> > new file mode 100644
> > index 0000000..6006bb4
> > --- /dev/null
> > +++ b/drivers/watchdog/sprd_wdt.c
> > @@ -0,0 +1,366 @@
> > +/*
> > + * Spreadtrum watchdog driver
> > + * Copyright (C) 2017 Spreadtrum - http://www.spreadtrum.com
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * 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/err.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/io.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/of_address.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/watchdog.h>
> > +
> > +#define WDT_LOAD_LOW		0x0
> > +#define WDT_LOAD_HIGH		0x4
> > +#define WDT_CTRL		0x8
> > +#define WDT_INT_CLR		0xc
> > +#define WDT_INT_RAW		0x10
> > +#define WDT_INT_MSK		0x14
> > +#define WDT_CNT_LOW		0x18
> > +#define WDT_CNT_HIGH		0x1c
> > +#define WDT_LOCK		0x20
> > +#define WDT_IRQ_LOAD_LOW	0x2c
> > +#define WDT_IRQ_LOAD_HIGH	0x30
> > +
> > +/* WDT_CTRL */
> > +#define WDT_INT_EN_BIT		BIT(0)
> > +#define WDT_CNT_EN_BIT		BIT(1)
> > +#define WDT_NEW_VER_EN		BIT(2)
> > +#define WDT_RST_EN_BIT		BIT(3)
> > +
> > +/* WDT_INT_CLR */
> > +#define WDT_INT_CLEAR_BIT	BIT(0)
> > +#define WDT_RST_CLEAR_BIT	BIT(3)
> > +
> > +/* WDT_INT_RAW */
> > +#define WDT_INT_RAW_BIT		BIT(0)
> > +#define WDT_RST_RAW_BIT		BIT(3)
> > +#define WDT_LD_BUSY_BIT		BIT(4)
> > +
> > +#define WDT_CLK			32768
> > +#define WDT_UNLOCK_KEY		0xe551
> > +#define WDT_IRQ_TMROUT_OFFSET	0x3
> > +
> > +#define WDT_CNT_VALUE_SIZE	16
> > +#define WDT_CNT_VALUE_MASK	GENMASK(15, 0)
> > +#define WDT_LOAD_TIMEOUT_NUM	10000
> > +
> > +struct sprd_wdt {
> > +	void __iomem *base;
> > +	struct watchdog_device wdd;
> > +	struct clk *enable;
> > +	struct clk *rtc_enable;
> > +	u32 irq_tmr_out;
> > +	u32 rst_tmr_out;
> > +	unsigned int irq;
> > +};
> > +
> > +static inline struct sprd_wdt *to_sprd_wdt(struct watchdog_device *wdd)
> > +{
> > +	return container_of(wdd, struct sprd_wdt, wdd);
> > +}
> > +
> > +static inline void sprd_wdt_lock(void __iomem *addr)
> > +{
> > +	writel_relaxed(0x0, addr + WDT_LOCK);
> > +}
> > +
> > +static inline void sprd_wdt_unlock(void __iomem *addr)
> > +{
> > +	writel_relaxed(WDT_UNLOCK_KEY, addr + WDT_LOCK);
> > +}
> > +
> > +static irqreturn_t sprd_wdt_isr(int irq, void *dev_id)
> > +{
> > +	struct sprd_wdt *wdt = (struct sprd_wdt *)dev_id;
> > +
> > +	sprd_wdt_unlock(wdt->base);
> > +	writel_relaxed(WDT_INT_CLEAR_BIT, wdt->base + WDT_INT_CLR);
> > +	sprd_wdt_lock(wdt->base);
> > +	watchdog_notify_pretimeout(&wdt->wdd);
> > +	return IRQ_HANDLED;
> > +}
> > +
> > +static u32 sprd_wdt_get_cnt_value(struct sprd_wdt *wdt)
> > +{
> > +	u32 val;
> > +
> > +	val = readl_relaxed(wdt->base + WDT_CNT_HIGH) << WDT_CNT_VALUE_SIZE;
> > +	val |= readl_relaxed(wdt->base + WDT_CNT_LOW) & WDT_CNT_VALUE_MASK;
> > +
> > +	return val;
> > +}
> > +
> > +static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 rst_value,
> > +			       u32 irq_value)
> > +{
> > +	u32 val, cnt = 0;
> > +
> > +	sprd_wdt_unlock(wdt->base);
> > +	writel_relaxed((rst_value >> WDT_CNT_VALUE_SIZE) & WDT_CNT_VALUE_MASK,
> > +		       wdt->base + WDT_LOAD_HIGH);
> > +	writel_relaxed((rst_value & WDT_CNT_VALUE_MASK),
> > +		       wdt->base + WDT_LOAD_LOW);
> > +	writel_relaxed((irq_value >> WDT_CNT_VALUE_SIZE) & WDT_CNT_VALUE_MASK,
> > +		       wdt->base + WDT_IRQ_LOAD_HIGH);
> > +	writel_relaxed(irq_value & WDT_CNT_VALUE_MASK,
> > +		       wdt->base + WDT_IRQ_LOAD_LOW);
> > +	sprd_wdt_lock(wdt->base);
> > +
> > +	/*
> > +	 * Waiting the load value operation done,
> > +	 * it needs two or three RTC clock cycles.
> > +	 */
> > +	do {
> > +		val = readl_relaxed(wdt->base + WDT_INT_RAW);
> > +		if (!(val & WDT_LD_BUSY_BIT))
> > +			break;
> > +
> > +		cpu_relax();
> > +	} while (cnt++ < WDT_LOAD_TIMEOUT_NUM);
> 
> This loop aborts when cnt >= WDT_LOAD_TIMEOUT_NUM, then increases cnt by 1.
> 
> > +
> > +	if (cnt == WDT_LOAD_TIMEOUT_NUM)
> 
> ... meaning this condition will never be met.
> 

Yes, you are right, and I will fix it in the next version.

> > +		return -EBUSY;
> > +	return 0;
> > +}
> > +
> > +static void sprd_wdt_enable(struct sprd_wdt *wdt)
> > +{
> > +	u32 val;
> > +
> > +	clk_prepare_enable(wdt->enable);
> > +	clk_prepare_enable(wdt->rtc_enable);
> > +
> > +	sprd_wdt_unlock(wdt->base);
> > +	val = readl_relaxed(wdt->base + WDT_CTRL);
> > +	val |= WDT_NEW_VER_EN;
> > +	writel_relaxed(val, wdt->base + WDT_CTRL);
> > +	sprd_wdt_lock(wdt->base);
> > +}
> > +
> > +static void sprd_wdt_disable(struct sprd_wdt *wdt)
> > +{
> > +	sprd_wdt_unlock(wdt->base);
> > +	writel_relaxed(0x0, wdt->base + WDT_CTRL);
> > +	sprd_wdt_lock(wdt->base);
> > +
> > +	clk_disable(wdt->enable);
> > +	clk_disable(wdt->rtc_enable);
> > +}
> > +
> > +static int sprd_wdt_start(struct watchdog_device *wdd)
> > +{
> > +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> > +	u32 val;
> > +	int ret;
> > +
> > +	ret = sprd_wdt_load_value(wdt, wdt->rst_tmr_out * WDT_CLK,
> > +			(wdt->rst_tmr_out - wdt->irq_tmr_out) * WDT_CLK);
> > +	if (ret)
> > +		return ret;
> > +
> > +	sprd_wdt_unlock(wdt->base);
> > +	val = readl_relaxed(wdt->base + WDT_CTRL);
> > +	val |= WDT_CNT_EN_BIT | WDT_INT_EN_BIT | WDT_RST_EN_BIT;
> > +	writel_relaxed(val, wdt->base + WDT_CTRL);
> > +	sprd_wdt_lock(wdt->base);
> > +
> > +	return 0;
> > +}
> > +
> > +static int sprd_wdt_stop(struct watchdog_device *wdd)
> > +{
> > +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> > +	u32 val;
> > +
> > +	sprd_wdt_unlock(wdt->base);
> > +	val = readl_relaxed(wdt->base + WDT_CTRL);
> > +	val &= ~(WDT_CNT_EN_BIT | WDT_RST_EN_BIT | WDT_INT_EN_BIT);
> > +	writel_relaxed(val, wdt->base + WDT_CTRL);
> > +	sprd_wdt_lock(wdt->base);
> > +	return 0;
> > +}
> > +
> > +static int sprd_wdt_set_timeout(struct watchdog_device *wdd,
> > +				u32 timeout)
> > +{
> > +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> > +
> > +	if (timeout < wdt->irq_tmr_out) {
> > +		dev_err(wdd->parent, "wrong timeout value\n");
> > +		return -EINVAL;
> > +	}
> > +
> If there is a minimum timeout, the probe function should set min_timeout accordingly.
> This function should not have to check the range, and it should not set a range error.
> 
> Also, wdd->timeout needs to be set here.
> 

You are right, it needs to set wdd->timeout, and I will use pretimerout instead of irq_tmr_out.

> > +	return sprd_wdt_load_value(wdt, timeout * WDT_CLK,
> > +			  (timeout - wdt->irq_tmr_out) * WDT_CLK);
> > +}
> > +
> > +static u32 sprd_wdt_get_timeleft(struct watchdog_device *wdd)
> > +{
> > +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> > +	u32 val;
> > +
> > +	val = sprd_wdt_get_cnt_value(wdt);
> > +	val = val / WDT_CLK;
> > +
> > +	return val;
> > +}
> > +
> > +static const struct watchdog_ops sprd_wdt_ops = {
> > +	.owner = THIS_MODULE,
> > +	.start = sprd_wdt_start,
> > +	.stop = sprd_wdt_stop,
> > +	.set_timeout = sprd_wdt_set_timeout,
> > +	.get_timeleft = sprd_wdt_get_timeleft,
> > +};
> > +
> > +static const struct watchdog_info sprd_wdt_info = {
> > +	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
> > +	.identity = "Spreadtrum Watchdog Timer",
> > +};
> > +
> > +static int sprd_wdt_probe(struct platform_device *pdev)
> > +{
> > +	struct resource *wdt_res;
> > +	struct sprd_wdt *wdt;
> > +	u32 rst_tmr_out;
> > +	int ret;
> > +
> > +	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
> > +	if (!wdt)
> > +		return -ENOMEM;
> > +
> > +	wdt_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	if (!wdt_res) {
> > +		dev_err(&pdev->dev, "failed to memory resource\n");
> > +		return -ENOMEM;
> > +	}
> > +
> > +	wdt->base = devm_ioremap_nocache(&pdev->dev, wdt_res->start,
> > +					 resource_size(wdt_res));
> > +	if (!wdt->base)
> > +		return -ENOMEM;
> > +
> > +	if (of_property_read_u32(pdev->dev.of_node, "timeout-sec",
> > +				 &rst_tmr_out)) {
> > +		dev_err(&pdev->dev, "can't get reset timeout\n");
> > +		return -EINVAL;
> > +	}
> 
> Please use the infrastructure to read and set this property.
> 

Yes, "timeout-sec" will be read out by watchdog_init_timeout.

> > +
> > +	wdt->enable = devm_clk_get(&pdev->dev, "enable");
> > +	if (IS_ERR(wdt->enable)) {
> > +		dev_err(&pdev->dev, "can't get the enable clock\n");
> > +		return PTR_ERR(wdt->enable);
> > +	}
> > +
> > +	wdt->rtc_enable = devm_clk_get(&pdev->dev, "rtc_enable");
> > +	if (IS_ERR(wdt->rtc_enable)) {
> > +		dev_err(&pdev->dev, "can't get the rtc enable clock\n");
> > +		return PTR_ERR(wdt->rtc_enable);
> > +	}
> > +
> > +	wdt->irq = platform_get_irq(pdev, 0);
> > +	if (wdt->irq < 0) {
> > +		dev_err(&pdev->dev, "failed to get IRQ resource\n");
> > +		return wdt->irq;
> > +	}
> > +
> > +	ret = devm_request_irq(&pdev->dev, wdt->irq, sprd_wdt_isr,
> > +			       IRQF_NO_SUSPEND, "sprd-wdt", (void *)wdt);
> > +	if (ret) {
> > +		dev_err(&pdev->dev, "failed to register irq\n");
> > +		return ret;
> > +	}
> > +
> > +	wdt->rst_tmr_out = rst_tmr_out;
> > +	wdt->irq_tmr_out = rst_tmr_out - WDT_IRQ_TMROUT_OFFSET;
> 
> Seems to me this is equivalent to pretimeout. Why not use the infrastructure ?
> Besides, this can currently get negative (if timeout is set to 1 or 2 seconds.
> 

I will use pretimeout instead of irq_tmr_out.

> > +	wdt->wdd.info = &sprd_wdt_info;
> > +	wdt->wdd.ops = &sprd_wdt_ops;
> > +	wdt->wdd.min_timeout = 1;
> > +	wdt->wdd.max_timeout = rst_tmr_out;
> > +	wdt->wdd.parent = &pdev->dev;
> > +	set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
> 
> Is it ? The clocks are not enabled (yet), and the start function hasn't been called.
> 
> Presumably the idea is to start the watchdog unconditionally, but then it is stopped
> after being opened and closed again, so I don't really understand the logic.
> 

OK, I will remove this line and I will set status bit as ACTIVE at sprd_wdt_enable.

> > +	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;
> > +	}
> > +
> > +	platform_set_drvdata(pdev, wdt);
> > +
> > +	sprd_wdt_enable(wdt);
> > +
> 
> This is racy; at least in theory user space can open the watchdog device
> immediately after it was registered, meaning the watchdog can be enabled
> before this code is executed. Maybe that is safe, but it may as well result
> in an error or hang since the clocks are still disabled.
> 
> Even more, WDOG_HW_RUNNING is set above, meaning the watchdog core will
> schedule an immediate ping (or start since there is no ping function),
> making this even more likely.
>

I understood your point, and I will fix it in next version.
 
> > +	return 0;
> > +}
> > +
> > +static int sprd_wdt_remove(struct platform_device *pdev)
> > +{
> > +	struct sprd_wdt *wdt = platform_get_drvdata(pdev);
> > +
> > +	watchdog_unregister_device(&wdt->wdd);
> > +
> 
> If the watchdog ws never opened, this won't stop the clocks.
> 

It should add one condition api here.

> > +	return 0;
> > +}
> > +
> > +static int __maybe_unused sprd_wdt_pm_suspend(struct device *dev)
> > +{
> > +	struct sprd_wdt *wdt = dev_get_drvdata(dev);
> > +
> > +	sprd_wdt_stop(&wdt->wdd);
> 
> Why stop the watchdog if it isn't running ?
> 

It should add one condition to check if watchdog is running.

> > +	sprd_wdt_disable(wdt);
> > +
> > +	return 0;
> > +}
> > +
> > +static int __maybe_unused sprd_wdt_pm_resume(struct device *dev)
> > +{
> > +	struct sprd_wdt *wdt = dev_get_drvdata(dev);
> > +
> > +	sprd_wdt_enable(wdt);
> > +	sprd_wdt_start(&wdt->wdd);
> 
> So on resume the watchdog is started unconditionally, even if it was
> not running before ?
>

It should add one condition to check if watchdog has been stop.
Very appreciated for your comments.
 
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct dev_pm_ops sprd_wdt_pm_ops = {
> > +	SET_SYSTEM_SLEEP_PM_OPS(
> > +		sprd_wdt_pm_suspend,
> > +		sprd_wdt_pm_resume)
> > +};
> > +
> > +static const struct of_device_id sprd_wdt_match_table[] = {
> > +	{ .compatible = "sprd,sp9860-wdt", },
> > +	{},
> > +};
> > +MODULE_DEVICE_TABLE(of, sprd_wdt_match_table);
> > +
> > +static struct platform_driver sprd_watchdog_driver = {
> > +	.probe	= sprd_wdt_probe,
> > +	.remove	= sprd_wdt_remove,
> > +	.driver	= {
> > +		.name = "sprd-wdt",
> > +		.of_match_table = sprd_wdt_match_table,
> > +		.pm = &sprd_wdt_pm_ops,
> > +	},
> > +};
> > +module_platform_driver(sprd_watchdog_driver);
> > +
> > +MODULE_AUTHOR("Eric Long <eric.long@...eadtrum.com>");
> > +MODULE_DESCRIPTION("Spreadtrum Watchdog Timer Controller Driver");
> > +MODULE_LICENSE("GPL v2");
> > 
> 

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