Re: [PATCH 2/3] watchdog: sam9x60_wdt: introduce sam9x60 watchdog timer driver

Eugen.Hristev
2019-10-02T11:08:03Z

On 02.10.2019 13:23, Alexandre Belloni wrote:

> Hi,
>
> On 02/10/2019 07:35:26+0000, Eugen.Hristev@microchip.com wrote:
>> +static void wdt_write(struct sam9x60_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);
>> + writel_relaxed(val, wdt->reg_base + field);
>> + wdt->last_ping = jiffies;
>> +}
>> +
>> +static void wdt_write_nosleep(struct sam9x60_wdt *wdt, u32 field, u32 val)
>> +{
>> + if (time_before(jiffies, wdt->last_ping + WDT_DELAY))
>> + usleep_range(123, 250);
>
> So you have a _nosleep function that does sleep?
>
>> + writel_relaxed(val, wdt->reg_base + field);
>> + wdt->last_ping = jiffies;
>> +}
>> +
>> +static int sam9x60_wdt_start(struct watchdog_device *wdd)
>> +{
>> + struct sam9x60_wdt *wdt = watchdog_get_drvdata(wdd);
>> +
>> + wdt->mr &= ~AT91_WDT_WDDIS;
>> + wdt_write(wdt, AT91_WDT_MR, wdt->mr);
>> + wdt_write_nosleep(wdt, AT91_WDT_IER, wdt->ir);
>
> I don't think AT91_WDT_IER needs to be protected, you can probably write
> it directly. Also, you certainly need to do that before starting the
> watchdog to avoid race conditions.
>
>> +
>> + return 0;
>> +}
>> +
>> +static int sam9x60_wdt_stop(struct watchdog_device *wdd)
>> +{
>> + struct sam9x60_wdt *wdt = watchdog_get_drvdata(wdd);
>> +
>> + wdt->mr |= AT91_WDT_WDDIS;
>> + wdt_write(wdt, AT91_WDT_MR, wdt->mr);
>> + wdt_write_nosleep(wdt, AT91_WDT_IDR, wdt->ir);
>> +
>
> I don't think AT91_WDT_IDR needs to be protected.
>
>> + return 0;
>> +}
>> +
>> +static int sam9x60_wdt_ping(struct watchdog_device *wdd)
>> +{
>> + struct sam9x60_wdt *wdt = watchdog_get_drvdata(wdd);
>> +
>> + wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
>> +
>> + return 0;
>> +}
>> +
>> +static int sam9x60_wdt_set_timeout(struct watchdog_device *wdd,
>> + unsigned int timeout)
>> +{
>> + struct sam9x60_wdt *wdt = watchdog_get_drvdata(wdd);
>> +
>> + wdt_write(wdt, AT91_WDT_WLR,
>> + AT91_WDT_SET_COUNTER(WDT_SEC2TICKS(timeout)));
>> +
>
> I don't think AT91_WDT_WLR needs to be protected.
>
>> + wdd->timeout = timeout;
>> +
>> + return 0;
>> +}
>> +
>> +static const struct watchdog_info sam9x60_wdt_info = {
>> + .options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
>> + .identity = "Microchip SAM9X60 Watchdog",
>> +};
>> +
>> +static const struct watchdog_ops sam9x60_wdt_ops = {
>> + .owner = THIS_MODULE,
>> + .start = sam9x60_wdt_start,
>> + .stop = sam9x60_wdt_stop,
>> + .ping = sam9x60_wdt_ping,
>> + .set_timeout = sam9x60_wdt_set_timeout,
>> +};
>> +
>> +static irqreturn_t sam9x60_wdt_irq_handler(int irq, void *dev_id)
>> +{
>> + struct sam9x60_wdt *wdt = platform_get_drvdata(dev_id);
>> +
>> + if (wdt_read(wdt, AT91_WDT_ISR)) {
>> + pr_crit("Microchip Watchdog Software Reset\n");
>> + emergency_restart();
>> + pr_crit("Reboot didn't succeed\n");
>> + }
>
> I'm not really convinced by the software restart use case but I guess it
> is to be able to shut down while still flushing data to the storage.
> This would not protect against kernel issues then.

Hi Alexandre,

That's correct. It is to do a software shutdown instead of hard reboot
by hardware. It has it;s use cases, so I preserved the same level of
functionality as in sama5d4_wdt

>
>> +
>> + return IRQ_HANDLED;
>> +}
>> +
>> +static int of_sam9x60_wdt_init(struct device_node *np, struct sam9x60_wdt *wdt)
>> +{
>> + const char *tmp;
>> +
>> + wdt->mr = AT91_WDT_WDDIS;
>> +
>> + if (!of_property_read_string(np, "atmel,watchdog-type", &tmp) &&
>> + !strcmp(tmp, "software"))
>> + wdt->ir = AT91_WDT_PERINT;
>> + else
>> + wdt->mr |= AT91_WDT_PERIODRST;
>> +
>> + 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 sam9x60_wdt_init(struct sam9x60_wdt *wdt)
>> +{
>> + u32 reg;
>> + /*
>> + * 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 (wdt_enabled) {
>> + wdt_write_nosleep(wdt, AT91_WDT_MR, wdt->mr);
>> + wdt_write_nosleep(wdt, AT91_WDT_IER, wdt->ir);
>> + wdt_write(wdt, AT91_WDT_WLR,
>> + AT91_WDT_SET_COUNTER(WDT_SEC2TICKS(WDT_DEFAULT_TIMEOUT)));
>> +
>> + } else {
>> + reg = wdt_read(wdt, AT91_WDT_MR);
>> + if (!(reg & AT91_WDT_WDDIS))
>> + wdt_write_nosleep(wdt, AT91_WDT_MR,
>> + reg | AT91_WDT_WDDIS);
>> + }
>> + return 0;
>> +}
>> +
>> +static int sam9x60_wdt_probe(struct platform_device *pdev)
>> +{
>> + struct watchdog_device *wdd;
>> + struct sam9x60_wdt *wdt;
>> + struct resource *res;
>> + void __iomem *regs;
>> + u32 irq = 0;
>> + int ret;
>> +
>> + wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
>> + if (!wdt)
>> + return -ENOMEM;
>> +
>> + wdd = &wdt->wdd;
>> + wdd->timeout = WDT_DEFAULT_TIMEOUT;
>> + wdd->info = &sam9x60_wdt_info;
>> + wdd->ops = &sam9x60_wdt_ops;
>> + wdd->min_timeout = MIN_WDT_TIMEOUT;
>> + wdd->max_timeout = MAX_WDT_TIMEOUT;
>> + wdt->last_ping = jiffies;
>> +
>> + watchdog_set_drvdata(wdd, wdt);
>> +
>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> + regs = devm_ioremap_resource(&pdev->dev, res);
>> + if (IS_ERR(regs))
>> + return PTR_ERR(regs);
>> +
>> + wdt->reg_base = regs;
>> +
>> + irq = irq_of_parse_and_map(pdev->dev.of_node, 0);
>> + if (!irq)
>> + dev_warn(&pdev->dev, "failed to get IRQ from DT\n");
>> +
>> + ret = of_sam9x60_wdt_init(pdev->dev.of_node, wdt);
>> + if (ret)
>> + return ret;
>> +
>> + if ((wdt->ir & AT91_WDT_PERINT) && irq) {
>> + ret = devm_request_irq(&pdev->dev, irq, sam9x60_wdt_irq_handler,
>> + IRQF_SHARED | IRQF_IRQPOLL |
>> + IRQF_NO_SUSPEND, pdev->name, pdev);
>> + if (ret) {
>> + dev_err(&pdev->dev,
>> + "cannot register interrupt handler\n");
>> + return ret;
>> + }
>> + }
>> +
>> + watchdog_init_timeout(wdd, wdt_timeout, &pdev->dev);
>> +
>> + ret = sam9x60_wdt_init(wdt);
>> + if (ret)
>> + return ret;
>> +
>> + watchdog_set_nowayout(wdd, nowayout);
>> +
>> + ret = watchdog_register_device(wdd);
>> + if (ret) {
>> + dev_err(&pdev->dev, "failed to register watchdog device\n");
>> + return ret;
>> + }
>> +
>> + platform_set_drvdata(pdev, wdt);
>> +
>> + dev_info(&pdev->dev, "initialized (timeout = %d sec, nowayout = %d)\n",
>> + wdd->timeout, nowayout);
>> +
>> + return 0;
>> +}
>> +
>> +static int sam9x60_wdt_remove(struct platform_device *pdev)
>> +{
>> + struct sam9x60_wdt *wdt = platform_get_drvdata(pdev);
>> +
>> + sam9x60_wdt_stop(&wdt->wdd);
>> +
>> + watchdog_unregister_device(&wdt->wdd);
>> +
>> + return 0;
>> +}
>> +
>> +static const struct of_device_id sam9x60_wdt_of_match[] = {
>> + { .compatible = "microchip,sam9x60-wdt", },
>> + { }
>> +};
>> +MODULE_DEVICE_TABLE(of, sam9x60_wdt_of_match);
>> +
>> +#ifdef CONFIG_PM_SLEEP
>
> Most of the logic has been copy/pasted from sama5d4_wdt.c and this
> already miss some improvement that have been made between the time you
> copied it and now.

I will fix accordingly. As I said in the commit message, sama5d4_wdt is
used as a starting point so yes, all the functionality is the same,
except the actual hardware interaction.

>
> Are you sure both drivers shouldn't be merged? I feel like this will be a
> maintenance hell if we don't do that now.

It could be merged, but we should do so ?
Could have two compatibles, with platform data, selectable, and with
different functions, that can be selected.. either this or that.
You think that's a better way to handle this new IP block ?
I would like to avoid having a big driver covering multiple different
hardware pieces, but that's just my preference. I can rework this into a
single driver if it's better that way.

Eugen

>
>> +static int sam9x60_wdt_resume(struct device *dev)
>> +{
>> + struct sam9x60_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.
>> + */
>> + sam9x60_wdt_init(wdt);
>> +
>> + return 0;
>> +}
>> +#endif
>> +
>> +static SIMPLE_DEV_PM_OPS(sam9x60_wdt_pm_ops, NULL,
>> + sam9x60_wdt_resume);
>> +
>> +static struct platform_driver sam9x60_wdt_driver = {
>> + .probe = sam9x60_wdt_probe,
>> + .remove = sam9x60_wdt_remove,
>> + .driver = {
>> + .name = "sam9x60_wdt",
>> + .pm = &sam9x60_wdt_pm_ops,
>> + .of_match_table = sam9x60_wdt_of_match,
>> + }
>> +};
>> +module_platform_driver(sam9x60_wdt_driver);
>> +
>> +MODULE_AUTHOR("Eugen Hristev");
>> +MODULE_DESCRIPTION("Microchip SAM9X60 Watchdog Timer driver");
>> +MODULE_LICENSE("GPL v2");
>> --
>> 2.7.4
>>
>