Re: [PATCH 2/3] watchdog: sama5d4_wdt: Refactor the driver

[Balakrishnan.S]

On 27/02/26 1:35 pm, Alexandre Belloni wrote:
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> 
> On 27/02/2026 13:01:15+0530, Balakrishnan Sambath wrote:
>> From: Andrei Simion <andrei.simion@xxxxxxxxxxxxx>
>>
>> This patch cleans up and refactors the Atmel SAMA5D4 Watchdog Driver
>> to be more readable and to fixup Reset issue introduced
>> by commit 266da53c35fc ("watchdog: sama5d4: readout initial state").
>>
>> Signed-off-by: Andrei Simion <andrei.simion@xxxxxxxxxxxxx>
>> [Use per-device WDDIS mask and sync MR shadow WDDIS state]
>> Signed-off-by: Balakrishnan Sambath <balakrishnan.s@xxxxxxxxxxxxx>
>> ---
>>   drivers/watchdog/sama5d4_wdt.c | 156 ++++++++++++++++-----------------
>>   1 file changed, 77 insertions(+), 79 deletions(-)
>>
>> diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
>> index 13e72918338a..b422d0bd75f9 100644
>> --- a/drivers/watchdog/sama5d4_wdt.c
>> +++ b/drivers/watchdog/sama5d4_wdt.c
>> @@ -24,44 +24,58 @@
>>   #define WDT_DEFAULT_TIMEOUT  MAX_WDT_TIMEOUT
>>
>>   #define WDT_SEC2TICKS(s)     ((s) ? (((s) << 8) - 1) : 0)
>>
>>   struct sama5d4_wdt {
>>        struct watchdog_device  wdd;
>>        void __iomem            *reg_base;
>>        u32                     mr;
>>        u32                     ir;
>> +     u32                     wddis_mask;
> 
> Introducing this should simply remove the need for 3/3, use this instead
> of AT91_WDT_WDDIS everywhere.

Okay, I'll keep this.

> 
>>        unsigned long           last_ping;
>>        bool                    need_irq;
>> -     bool                    sam9x60_support;
>> +     bool                    is_modern_chip;
> 
> The previous name was better.

Got it, I'll address this as it seems meaningful to retain Soc level 
details too.
> 
>>   };
>>
>> +static inline bool wdt_enabled(struct sama5d4_wdt *wdt, u32 mr)
>> +{
>> +     return !(mr & wdt->wddis_mask);
>> +}
>> +
> 
> This is unrelated to the actual fix. This patch does to much and is
> difficult to review and to backport, please separate the actual fix
> about wddis and the rest.

My bad, I'll refactor the fix and refactor as separate chunks in v2.

> 
> 
>>   static int wdt_timeout;
>>   static bool nowayout = WATCHDOG_NOWAYOUT;
>>
>>   module_param(wdt_timeout, int, 0);
>>   MODULE_PARM_DESC(wdt_timeout,
>>        "Watchdog timeout in seconds. (default = "
>>        __MODULE_STRING(WDT_DEFAULT_TIMEOUT) ")");
>>
>>   module_param(nowayout, bool, 0);
>>   MODULE_PARM_DESC(nowayout,
>>        "Watchdog cannot be stopped once started (default="
>>        __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
>>
>> -#define wdt_enabled (!(wdt->mr & AT91_WDT_WDDIS))
>>
>>   #define wdt_read(wdt, field) \
>>        readl_relaxed((wdt)->reg_base + (field))
>>
>>   /* 4 slow clock periods is 4/32768 = 122.07µs*/
>>   #define WDT_DELAY    usecs_to_jiffies(123)
>>
>> +static bool check_is_modern_chip_by_compatible(struct device *dev)
>> +{
>> +     if (of_device_is_compatible(dev->of_node, "microchip,sam9x60-wdt") ||
>> +         of_device_is_compatible(dev->of_node, "microchip,sama7g5-wdt"))
>> +             return true;
>> +
>> +     return false;
>> +}
>> +
>>   static void wdt_write(struct sama5d4_wdt *wdt, u32 field, u32 val)
>>   {
>>        /*
>>         * WDT_CR and WDT_MR must not be modified within three slow clock
>>         * periods following a restart of the watchdog performed by a write
>>         * access in WDT_CR.
>>         */
>>        while (time_before(jiffies, wdt->last_ping + WDT_DELAY))
>>                usleep_range(30, 125);
>> @@ -71,322 +85,306 @@ static void wdt_write(struct sama5d4_wdt *wdt, u32 field, u32 val)
>>
>>   static void wdt_write_nosleep(struct sama5d4_wdt *wdt, u32 field, u32 val)
>>   {
>>        if (time_before(jiffies, wdt->last_ping + WDT_DELAY))
>>                udelay(123);
>>        writel_relaxed(val, wdt->reg_base + field);
>>        wdt->last_ping = jiffies;
>>   }
>>
>> -static int sama5d4_wdt_start(struct watchdog_device *wdd)
>> +static int wdt_start(struct watchdog_device *wdd)
>>   {
>>        struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
>>
>> -     if (wdt->sam9x60_support) {
>> -             writel_relaxed(wdt->ir, wdt->reg_base + AT91_SAM9X60_IER);
>> -             wdt->mr &= ~AT91_SAM9X60_WDDIS;
>> -     } else {
>> -             wdt->mr &= ~AT91_WDT_WDDIS;
>> -     }
>> +     if (wdt->is_modern_chip)
>> +             writel_relaxed(wdt->ir, wdt->reg_base + AT91_WDT_IER);
>> +     wdt->mr &= ~wdt->wddis_mask;
>>        wdt_write(wdt, AT91_WDT_MR, wdt->mr);
>>
>>        return 0;
>>   }
>>
>> -static int sama5d4_wdt_stop(struct watchdog_device *wdd)
>> +static int wdt_stop(struct watchdog_device *wdd)
>>   {
>>        struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
>>
>> -     if (wdt->sam9x60_support) {
>> -             writel_relaxed(wdt->ir, wdt->reg_base + AT91_SAM9X60_IDR);
>> -             wdt->mr |= AT91_SAM9X60_WDDIS;
>> -     } else {
>> -             wdt->mr |= AT91_WDT_WDDIS;
>> -     }
>> +     if (wdt->is_modern_chip)
>> +             writel_relaxed(wdt->ir, wdt->reg_base + AT91_WDT_IDR);
>> +     wdt->mr |= wdt->wddis_mask;
>>        wdt_write(wdt, AT91_WDT_MR, wdt->mr);
>>
>>        return 0;
>>   }
>>
>> -static int sama5d4_wdt_ping(struct watchdog_device *wdd)
>> +static int wdt_ping(struct watchdog_device *wdd)
>>   {
>>        struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
>>
>>        wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
>>
>>        return 0;
>>   }
>>
>> -static int sama5d4_wdt_set_timeout(struct watchdog_device *wdd,
>> -                              unsigned int timeout)
>> +static int wdt_set_timeout(struct watchdog_device *wdd,
>> +                        unsigned int timeout)
>>   {
>>        struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
>>        u32 value = WDT_SEC2TICKS(timeout);
>>
>> -     if (wdt->sam9x60_support) {
>> -             wdt_write(wdt, AT91_SAM9X60_WLR,
>> -                       AT91_SAM9X60_SET_COUNTER(value));
>> +     if (wdt->is_modern_chip) {
>> +             wdt_write(wdt, AT91_WDT_WLR,
>> +                       AT91_WDT_SET_COUNTER(value));
>>
>>                wdd->timeout = timeout;
>>                return 0;
>>        }
>>
>>        wdt->mr &= ~AT91_WDT_WDV;
>>        wdt->mr |= AT91_WDT_SET_WDV(value);
>>
>>        /*
>>         * WDDIS has to be 0 when updating WDD/WDV. The datasheet states: When
>>         * setting the WDDIS bit, and while it is set, the fields WDV and WDD
>>         * must not be modified.
>>         * If the watchdog is enabled, then the timeout can be updated. Else,
>>         * wait that the user enables it.
>>         */
>> -     if (wdt_enabled)
>> -             wdt_write(wdt, AT91_WDT_MR, wdt->mr & ~AT91_WDT_WDDIS);
>> +     if (wdt_enabled(wdt, wdt->mr))
>> +             wdt_write(wdt, AT91_WDT_MR, wdt->mr & ~wdt->wddis_mask);
>>
>>        wdd->timeout = timeout;
>>
>>        return 0;
>>   }
>>
>>   static const struct watchdog_info sama5d4_wdt_info = {
>>        .options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
>>        .identity = "Atmel SAMA5D4 Watchdog",
>>   };
>>
>>   static const struct watchdog_ops sama5d4_wdt_ops = {
>>        .owner = THIS_MODULE,
>> -     .start = sama5d4_wdt_start,
>> -     .stop = sama5d4_wdt_stop,
>> -     .ping = sama5d4_wdt_ping,
>> -     .set_timeout = sama5d4_wdt_set_timeout,
>> +     .start = wdt_start,
>> +     .stop = wdt_stop,
>> +     .ping = wdt_ping,
>> +     .set_timeout = wdt_set_timeout,
>>   };
>>
>> -static irqreturn_t sama5d4_wdt_irq_handler(int irq, void *dev_id)
>> +static irqreturn_t wdt_irq_handler(int irq, void *dev_id)
>>   {
>>        struct sama5d4_wdt *wdt = platform_get_drvdata(dev_id);
>>        u32 reg;
>>
>> -     if (wdt->sam9x60_support)
>> -             reg = wdt_read(wdt, AT91_SAM9X60_ISR);
>> +     if (wdt->is_modern_chip)
>> +             reg = wdt_read(wdt, AT91_WDT_ISR);
>>        else
>>                reg = wdt_read(wdt, AT91_WDT_SR);
>>
>>        if (reg) {
>>                pr_crit("Atmel Watchdog Software Reset\n");
>>                emergency_restart();
>>                pr_crit("Reboot didn't succeed\n");
>>        }
>>
>>        return IRQ_HANDLED;
>>   }
>>
>> -static int of_sama5d4_wdt_init(struct device_node *np, struct sama5d4_wdt *wdt)
>> +static int of_wdt_init(struct device_node *np, struct sama5d4_wdt *wdt)
>>   {
>>        const char *tmp;
>>
>> -     if (wdt->sam9x60_support)
>> -             wdt->mr = AT91_SAM9X60_WDDIS;
>> -     else
>> -             wdt->mr = AT91_WDT_WDDIS;
>> +     wdt->mr = wdt->wddis_mask;
>>
>>        if (!of_property_read_string(np, "atmel,watchdog-type", &tmp) &&
>>            !strcmp(tmp, "software"))
>>                wdt->need_irq = true;
>>
>>        if (of_property_read_bool(np, "atmel,idle-halt"))
>>                wdt->mr |= AT91_WDT_WDIDLEHLT;
>>
>>        if (of_property_read_bool(np, "atmel,dbg-halt"))
>>                wdt->mr |= AT91_WDT_WDDBGHLT;
>>
>>        return 0;
>>   }
>>
>> -static int sama5d4_wdt_init(struct sama5d4_wdt *wdt)
>> +static int wdt_init(struct sama5d4_wdt *wdt)
>>   {
>> +     struct watchdog_device *wdd = &wdt->wdd;
>>        u32 reg, val;
>>
>>        val = WDT_SEC2TICKS(WDT_DEFAULT_TIMEOUT);
>> +
>>        /*
>>         * When booting and resuming, the bootloader may have changed the
>>         * watchdog configuration.
>> -      * If the watchdog is already running, we can safely update it.
>> -      * Else, we have to disable it properly.
>> +      * If the watchdog is not running, we need to disable it properly.
>> +      * Otherwise, we can safely update it.
>>         */
>> -     if (!wdt_enabled) {
>> -             reg = wdt_read(wdt, AT91_WDT_MR);
>> -             if (wdt->sam9x60_support && (!(reg & AT91_SAM9X60_WDDIS)))
>> -                     wdt_write_nosleep(wdt, AT91_WDT_MR,
>> -                                       reg | AT91_SAM9X60_WDDIS);
>> -             else if (!wdt->sam9x60_support &&
>> -                      (!(reg & AT91_WDT_WDDIS)))
>> -                     wdt_write_nosleep(wdt, AT91_WDT_MR,
>> -                                       reg | AT91_WDT_WDDIS);
>> +     reg = wdt_read(wdt, AT91_WDT_MR);
>> +     if (wdt_enabled(wdt, reg)) {
>> +             wdt->mr &= ~wdt->wddis_mask;
>> +             set_bit(WDOG_HW_RUNNING, &wdd->status);
>> +     } else {
>> +             wdt->mr |= wdt->wddis_mask;
>>        }
>>
>> -     if (wdt->sam9x60_support) {
>> +     if (wdt->is_modern_chip) {
>>                if (wdt->need_irq)
>> -                     wdt->ir = AT91_SAM9X60_PERINT;
>> +                     wdt->ir = AT91_WDT_PERINT;
>>                else
>> -                     wdt->mr |= AT91_SAM9X60_PERIODRST;
>> +                     wdt->mr |= AT91_WDT_PERIODRST;
>>
>> -             wdt_write(wdt, AT91_SAM9X60_IER, wdt->ir);
>> -             wdt_write(wdt, AT91_SAM9X60_WLR, AT91_SAM9X60_SET_COUNTER(val));
>> +             wdt_write(wdt, AT91_WDT_IER, wdt->ir);
>> +             wdt_write(wdt, AT91_WDT_WLR, AT91_WDT_SET_COUNTER(val));
>>        } else {
>>                wdt->mr |= AT91_WDT_SET_WDD(WDT_SEC2TICKS(MAX_WDT_TIMEOUT));
>>                wdt->mr |= AT91_WDT_SET_WDV(val);
>>
>>                if (wdt->need_irq)
>>                        wdt->mr |= AT91_WDT_WDFIEN;
>>                else
>>                        wdt->mr |= AT91_WDT_WDRSTEN;
>>        }
>>
>>        wdt_write_nosleep(wdt, AT91_WDT_MR, wdt->mr);
>>
>>        return 0;
>>   }
>>
>> -static int sama5d4_wdt_probe(struct platform_device *pdev)
>> +static int wdt_probe(struct platform_device *pdev)
>>   {
>>        struct device *dev = &pdev->dev;
>>        struct watchdog_device *wdd;
>>        struct sama5d4_wdt *wdt;
>>        void __iomem *regs;
>>        u32 irq = 0;
>> -     u32 reg;
>>        int ret;
>>
>>        wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
>>        if (!wdt)
>>                return -ENOMEM;
>>
>>        wdd = &wdt->wdd;
>>        wdd->timeout = WDT_DEFAULT_TIMEOUT;
>>        wdd->info = &sama5d4_wdt_info;
>>        wdd->ops = &sama5d4_wdt_ops;
>>        wdd->min_timeout = MIN_WDT_TIMEOUT;
>>        wdd->max_timeout = MAX_WDT_TIMEOUT;
>>        wdt->last_ping = jiffies;
>> -
>> -     if (of_device_is_compatible(dev->of_node, "microchip,sam9x60-wdt") ||
>> -         of_device_is_compatible(dev->of_node, "microchip,sama7g5-wdt"))
>> -             wdt->sam9x60_support = true;
>> +     wdt->is_modern_chip = check_is_modern_chip_by_compatible(dev);
>> +     if (wdt->is_modern_chip)
>> +             wdt->wddis_mask = AT91_WDT_WDDIS_MODERN;
>> +     else
>> +             wdt->wddis_mask = AT91_WDT_WDDIS_LEGACY;
>>
>>        watchdog_set_drvdata(wdd, wdt);
>>
>>        regs = devm_platform_ioremap_resource(pdev, 0);
>>        if (IS_ERR(regs))
>>                return PTR_ERR(regs);
>>
>>        wdt->reg_base = regs;
>>
>> -     ret = of_sama5d4_wdt_init(dev->of_node, wdt);
>> +     ret = of_wdt_init(dev->of_node, wdt);
>>        if (ret)
>>                return ret;
>>
>>        if (wdt->need_irq) {
>>                irq = irq_of_parse_and_map(dev->of_node, 0);
>>                if (!irq) {
>>                        dev_warn(dev, "failed to get IRQ from DT\n");
>>                        wdt->need_irq = false;
>>                }
>>        }
>>
>>        if (wdt->need_irq) {
>> -             ret = devm_request_irq(dev, irq, sama5d4_wdt_irq_handler,
>> +             ret = devm_request_irq(dev, irq, wdt_irq_handler,
>>                                       IRQF_SHARED | IRQF_IRQPOLL |
>>                                       IRQF_NO_SUSPEND, pdev->name, pdev);
>>                if (ret) {
>>                        dev_err(dev, "cannot register interrupt handler\n");
>>                        return ret;
>>                }
>>        }
>>
>>        watchdog_init_timeout(wdd, wdt_timeout, dev);
>>
>> -     reg = wdt_read(wdt, AT91_WDT_MR);
>> -     if (!(reg & AT91_WDT_WDDIS)) {
>> -             wdt->mr &= ~AT91_WDT_WDDIS;
>> -             set_bit(WDOG_HW_RUNNING, &wdd->status);
>> -     }
>> -
>> -     ret = sama5d4_wdt_init(wdt);
>> +     ret = wdt_init(wdt);
>>        if (ret)
>>                return ret;
>>
>>        watchdog_set_nowayout(wdd, nowayout);
>>
>>        watchdog_stop_on_unregister(wdd);
>>        ret = devm_watchdog_register_device(dev, wdd);
>>        if (ret)
>>                return ret;
>>
>>        platform_set_drvdata(pdev, wdt);
>>
>>        dev_info(dev, "initialized (timeout = %d sec, nowayout = %d)\n",
>>                 wdd->timeout, nowayout);
>>
>>        return 0;
>>   }
>>
>> -static const struct of_device_id sama5d4_wdt_of_match[] = {
>> +static const struct of_device_id wdt_of_match[] = {
>>        {
>>                .compatible = "atmel,sama5d4-wdt",
>>        },
>>        {
>>                .compatible = "microchip,sam9x60-wdt",
>>        },
>>        {
>>                .compatible = "microchip,sama7g5-wdt",
>>        },
>>
>>        { }
>>   };
>> -MODULE_DEVICE_TABLE(of, sama5d4_wdt_of_match);
>> +MODULE_DEVICE_TABLE(of, wdt_of_match);
>>
>> -static int sama5d4_wdt_suspend_late(struct device *dev)
>> +static int wdt_suspend_late(struct device *dev)
>>   {
>>        struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
>>
>>        if (watchdog_active(&wdt->wdd))
>> -             sama5d4_wdt_stop(&wdt->wdd);
>> +             wdt_stop(&wdt->wdd);
>>
>>        return 0;
>>   }
>>
>> -static int sama5d4_wdt_resume_early(struct device *dev)
>> +static int wdt_resume_early(struct device *dev)
>>   {
>>        struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
>>
>>        /*
>>         * FIXME: writing MR also pings the watchdog which may not be desired.
>>         * This should only be done when the registers are lost on suspend but
>>         * there is no way to get this information right now.
>>         */
>> -     sama5d4_wdt_init(wdt);
>> +     wdt_init(wdt);
>>
>>        if (watchdog_active(&wdt->wdd))
>> -             sama5d4_wdt_start(&wdt->wdd);
>> +             wdt_start(&wdt->wdd);
>>
>>        return 0;
>>   }
>>
>>   static const struct dev_pm_ops sama5d4_wdt_pm_ops = {
>> -     LATE_SYSTEM_SLEEP_PM_OPS(sama5d4_wdt_suspend_late,
>> -                              sama5d4_wdt_resume_early)
>> +     LATE_SYSTEM_SLEEP_PM_OPS(wdt_suspend_late,
>> +                              wdt_resume_early)
>>   };
>>
>>   static struct platform_driver sama5d4_wdt_driver = {
>> -     .probe          = sama5d4_wdt_probe,
>> +     .probe          = wdt_probe,
>>        .driver         = {
>>                .name   = "sama5d4_wdt",
>>                .pm     = pm_sleep_ptr(&sama5d4_wdt_pm_ops),
>> -             .of_match_table = sama5d4_wdt_of_match,
>> +             .of_match_table = wdt_of_match,
>>        }
>>   };
>>   module_platform_driver(sama5d4_wdt_driver);
>>
>>   MODULE_AUTHOR("Atmel Corporation");
>>   MODULE_DESCRIPTION("Atmel SAMA5D4 Watchdog Timer driver");
>>   MODULE_LICENSE("GPL v2");
>> --
>> 2.34.1
>>
> 
> --
> Alexandre Belloni, co-owner and COO, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com