Re: [PATCH v3 2/2] watchdog: Add Spreadtrum watchdog driver
From: Guenter Roeck
Date: Mon Oct 30 2017 - 05:32:49 EST
On 10/30/2017 02:18 AM, Baolin Wang wrote:
Hi Guenter,
(There are some problem with Eric's email, he can not receive this
email, so I help to reply his comments following yours. sorry for
troubles.)
+#define SPRD_WDT_MAX_TIMEOUT 60
Is that really the maximum supported timeout ? Seems a bit low.
Shouldn't it be something like (U32_MAX / SPRD_WDT_CNT_STEP) ?
It supports the max value like as U32_MAX/SPRD_WDT_CNT_STEP,
but it doesn't unnecessary to support so big value, if the system can not
response it in 60s, the watchdog could trigger timeout.
It is customary to provide the highest possible value here.
No one is forced to set such high values. You are making a choice for
others here. But, sure, if you insist; not worth arguing about.
Eric said 60s is better for us, thanks for your patient explanation.
+
+#define SPRD_WDT_CNT_HIGH_VALUE 16
Maybe name it "SPRD_WDT_CNT_HIGH_SHIFT". It is not really a value,
it is a shift.
Yes, you are right, _SHIFT will be better.
+#define SPRD_WDT_LOW_VALUE_MASK GENMASK(15, 0)
+#define SPRD_WDT_CNT_VALUE_MAX GENMASK(31, 0)
Does this mask serve a useful purpose ?
OK, I will remove it, thanks!
+#define SPRD_WDT_LOAD_TIMEOUT 1000
+
+struct sprd_wdt {
+ void __iomem *base;
+ struct watchdog_device wdd;
+ struct clk *enable;
+ struct clk *rtc_enable;
+ 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 + SPRD_WDT_LOCK);
+}
+
+static inline void sprd_wdt_unlock(void __iomem *addr)
+{
+ writel_relaxed(SPRD_WDT_UNLOCK_KEY, addr + SPRD_WDT_LOCK);
+}
+
+static inline bool sprd_wdt_is_running(struct sprd_wdt *wdt)
+{
+ u32 val;
+
+ val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
+ return val & SPRD_WDT_NEW_VER_EN;
+}
+
+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(SPRD_WDT_INT_CLEAR_BIT, wdt->base +
SPRD_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 + SPRD_WDT_CNT_HIGH) <<
+ SPRD_WDT_CNT_HIGH_VALUE;
+ val |= readl_relaxed(wdt->base + SPRD_WDT_CNT_LOW) &
+ SPRD_WDT_LOW_VALUE_MASK;
+
+ return val;
+}
+
+static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 timeout,
+ u32 pretimeout)
+{
+ u32 val, delay_cnt = 0;
+ u32 tmr_step = timeout * SPRD_WDT_CNT_STEP;
+ u32 prtmr_step = pretimeout * SPRD_WDT_CNT_STEP;
+
+ sprd_wdt_unlock(wdt->base);
+ writel_relaxed((tmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
+ SPRD_WDT_LOW_VALUE_MASK, wdt->base +
SPRD_WDT_LOAD_HIGH);
+ writel_relaxed((tmr_step & SPRD_WDT_LOW_VALUE_MASK),
+ wdt->base + SPRD_WDT_LOAD_LOW);
+ writel_relaxed((prtmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
+ SPRD_WDT_LOW_VALUE_MASK,
+ wdt->base + SPRD_WDT_IRQ_LOAD_HIGH);
+ writel_relaxed(prtmr_step & SPRD_WDT_LOW_VALUE_MASK,
+ wdt->base + SPRD_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 + SPRD_WDT_INT_RAW);
+ if (!(val & SPRD_WDT_LD_BUSY_BIT))
+ break;
+
+ cpu_relax();
+ } while (delay_cnt++ < SPRD_WDT_LOAD_TIMEOUT);
+
+ if (delay_cnt >= SPRD_WDT_LOAD_TIMEOUT)
+ return -EBUSY;
+ return 0;
+}
+
+static int sprd_wdt_enable(struct sprd_wdt *wdt)
+{
+ u32 val;
+ int ret;
+
+ ret = clk_prepare_enable(wdt->enable);
+ if (ret)
+ return ret;
+ ret = clk_prepare_enable(wdt->rtc_enable);
+ if (ret)
+ return ret;
+
+ sprd_wdt_unlock(wdt->base);
+ val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
+ val |= SPRD_WDT_NEW_VER_EN;
+ writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
+ sprd_wdt_lock(wdt->base);
+ return 0;
+}
+
+static void sprd_wdt_disable(struct sprd_wdt *wdt)
+{
+ sprd_wdt_unlock(wdt->base);
+ writel_relaxed(0x0, wdt->base + SPRD_WDT_CTRL);
+ sprd_wdt_lock(wdt->base);
+
+ clk_disable_unprepare(wdt->rtc_enable);
+ clk_disable_unprepare(wdt->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, wdd->timeout, wdd->pretimeout);
+ if (ret)
+ return ret;
+
+ sprd_wdt_unlock(wdt->base);
+ val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
+ val |= SPRD_WDT_CNT_EN_BIT | SPRD_WDT_INT_EN_BIT |
SPRD_WDT_RST_EN_BIT;
+ writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
+ sprd_wdt_lock(wdt->base);
+ set_bit(WDOG_HW_RUNNING, &wdd->status);
+
+ 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 + SPRD_WDT_CTRL);
+ val &= ~(SPRD_WDT_CNT_EN_BIT | SPRD_WDT_RST_EN_BIT |
+ SPRD_WDT_INT_EN_BIT);
+ writel_relaxed(val, wdt->base + SPRD_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 == wdd->timeout)
+ return 0;
+
+ wdd->timeout = timeout;
+
+ return sprd_wdt_load_value(wdt, timeout, wdd->pretimeout);
+}
+
+static int sprd_wdt_set_pretimeout(struct watchdog_device *wdd,
+ u32 new_pretimeout)
+{
+ struct sprd_wdt *wdt = to_sprd_wdt(wdd);
+
+ if (new_pretimeout == wdd->pretimeout)
+ return 0;
This is inconsistent. pretimeout == 0 is accepted until it is set
to a non-zero value once, then 0 is no longer accepted. pretimeout==0
should reflect "pretimeout disabled". If that is not possible you
need to set some non-0 default value in the probe function.
I understand your opinion, I will fix it.
+ if (new_pretimeout <= wdd->min_timeout)
+ return -EINVAL;
Why is pretimeout == wdd->min_timeout invalid ?
OK, you are right, it should be pretimeout < min_timeout.
+
+ wdd->pretimeout = new_pretimeout;
+
+ return sprd_wdt_load_value(wdt, wdd->timeout, new_pretimeout);
+}
+
+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 / SPRD_WDT_CNT_STEP;
+
+ 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,
+ .set_pretimeout = sprd_wdt_set_pretimeout,
+ .get_timeleft = sprd_wdt_get_timeleft,
Just wondering - no heartbeat function ? Having to load the timer
values for each heartbeat is expensive.
Unfortunately, this watchdog has not RELOAD register.
+};
+
+static const struct watchdog_info sprd_wdt_info = {
+ .options = WDIOF_SETTIMEOUT |
+ WDIOF_PRETIMEOUT |
+ 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;
+ 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;
+ }
Unnecessary error check and message. devm_ioremap_resource()
returns an error if res is NULL.
OK, I will fix it.
+
+ wdt->base = devm_ioremap_resource(&pdev->dev, wdt_res);
+ if (IS_ERR(wdt->base))
Move the error message to here.
+ return PTR_ERR(wdt->base);
+
+ 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->wdd.info = &sprd_wdt_info;
+ wdt->wdd.ops = &sprd_wdt_ops;
+ wdt->wdd.parent = &pdev->dev;
+ wdt->wdd.min_timeout = SPRD_WDT_MIN_TIMROUT;
+ wdt->wdd.max_timeout = SPRD_WDT_MAX_TIMEOUT;
+
You might want to set wdt->wdd.timeout to a default value.
OK, I will set a default timeout value in case of no timeout-sec in
device-tree.
+ ret = sprd_wdt_enable(wdt);
+ if (ret) {
+ dev_err(&pdev->dev, "failed to enable wdt\n");
+ return ret;
+ }
+
This needs a matching sprd_wdt_disable() call in the remove function.
Best way to handle this would be to add devm_add_action() here.
If add devm_add_action(), it will be called in the remove function,
but this is not our expect, if someone remove this module, we want it just
timeout.
But that leaves the watchdog enabled even if it was stopped (no call to
sprd_wdt_disable()).
Eric said It can not be stopped since we have set WATCHDOG_NOWAYOUT,
which means it will reboot the system when removing the watchdog.
Relying on NOWAYOUT would be a better option here. Again, you are
making a choice for the user.
we have set WATCHDOG_NOWAYOUT.
Yes, I understand, but that is configurable.
Guenter
+ watchdog_set_nowayout(&wdt->wdd, WATCHDOG_NOWAYOUT);
+ watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
+
+ ret = watchdog_register_device(&wdt->wdd);
Unfortunately this doesn't work. It leaves interrupts enabled
after the watchdog device is removed in sprd_wdt_remove(),
but the driver will be gone. I would suggest to use
devm_watchdog_register_device() and reorder calls to request
the interrupt after registering the watchdog device. Then you
can drop the remove function entirely.
Yes, you are right, I understand your opinion, and it is very important,
devm_watchdog_register_device() is better. Thanks.
+ if (ret) {
+ sprd_wdt_disable(wdt);
+ dev_err(&pdev->dev, "failed to register watchdog\n");
+ return ret;
+ }
+ platform_set_drvdata(pdev, wdt);
+
+ 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 (sprd_wdt_is_running(wdt))
+ dev_crit(&pdev->dev, "Device removed: Expect
reboot!\n");
+ return 0;
+}
+
+static int __maybe_unused sprd_wdt_pm_suspend(struct device *dev)
+{
+ struct watchdog_device *wdd = dev_get_drvdata(dev);
+ struct sprd_wdt *wdt = dev_get_drvdata(dev);
+
+ if (watchdog_active(wdd)) {
+ sprd_wdt_stop(&wdt->wdd);
+ sprd_wdt_disable(wdt);
Are you sure you only want to disable the clocks if the watchdog was
active ?
That seems to be a bit inconsistent.
This watchdog is in always on power domain, if system suspend, it needs to
disable it, or it will timeout.
That is not what I asked. I asked why it isn't
if (watchdog_active(wdd))
sprd_wdt_stop(&wdt->wdd);
sprd_wdt_disable(wdt);
instead.
Yes, Eric will fix this in next version.
+ }
+
+ return 0;
+}
+
+static int __maybe_unused sprd_wdt_pm_resume(struct device *dev)
+{
+ struct watchdog_device *wdd = dev_get_drvdata(dev);
+ struct sprd_wdt *wdt = dev_get_drvdata(dev);
+ int ret;
+
+ if (watchdog_active(wdd)) {
+ ret = sprd_wdt_enable(wdt);
+ if (ret)
+ return ret;
+ ret = sprd_wdt_start(&wdt->wdd);
+ if (ret) {
+ sprd_wdt_disable(wdt);
+ return ret;
+ }
This can leave the system in an inconsistent state. Sometimes the wdt may
be
disabled, sometimes not.
If watchdog enable failed, it means there is something wrong in this
system.
True.
Guenter