Hi Ahmad,
On Mon, Nov 04, 2019 at 11:14:05PM +0100, Ahmad Fatoum wrote:
> Linux watchdog have an optional WDOG_HW_RUNNING bit that is used in
> conjunction with CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED to automatically
> ping running watchdogs until userspace takes over.
>
> So far, when we ported Linux drivers, we dropped this detection, but it
> would be useful to have this information in barebox as well:
>
> The American Megatrends BIOS I am using allows configuring the hardware
> watchdog from the BIOS. barebox enables the WDT as well, so in normal
> operation we would never notice if after a BIOS update, the watchdog is
> no longer enabled. If we maintain a running parameter on watchdog
> devices, board code can be written to check whether the watchdog device
> is indeed running.
To write such code I would prefer to have a function which returns the
running status rather than playing with getenv(). Additionally there is
a function missing in the watchdog code which returns a watchdog by its
name. This can be a future excercise, no need to do it in this patch.
> @@ -45,7 +47,18 @@ int watchdog_set_timeout(struct watchdog *wd, unsigned timeout)
>
> pr_debug("setting timeout on %s to %ds\n", watchdog_name(wd), timeout);
>
> - return wd->set_timeout(wd, timeout);
> + ret = wd->set_timeout(wd, timeout);
> + if (ret)
> + return ret;
> +
> + if (test_bit(WDOG_HW_RUNNING_SUPPORTED, &wd->status)) {
> + if (timeout)
> + set_bit(WDOG_HW_RUNNING, &wd->status);
> + else
> + clear_bit(WDOG_HW_RUNNING, &wd->status);
> + }
When we just started the watchdog we actually know that it is running,
so we could support the parameter for all watchdogs once it's started.
> +
> + return 0;
> }
> EXPORT_SYMBOL(watchdog_set_timeout);
>
> @@ -118,6 +131,15 @@ static int watchdog_register_poller(struct watchdog *wd)
> return PTR_ERR_OR_ZERO(p);
> }
>
> +static const char *watchdog_get_running(struct device_d *dev, struct param_d *p)
> +{
> + /*
> + * This won't ever fail, because the parameter is only registed when
> + * test_bit(WDOG_HW_RUNNING_SUPPORTED, &w->status) is true
> + */
> + return watchdog_hw_running((struct watchdog *)p->value) ? "1" : "0";
> +}
Casting p->value to (struct watchdog *) seems wrong. However, this
function shouldn't be needed, see below.
> +
> static int watchdog_register_dev(struct watchdog *wd, const char *name, int id)
> {
> wd->dev.parent = wd->hwdev;
> @@ -162,6 +184,15 @@ int watchdog_register(struct watchdog *wd)
> if (ret)
> return ret;
>
> + if (test_bit(WDOG_HW_RUNNING_SUPPORTED, &wd->status)) {
> + p = dev_add_param(&wd->dev, "running", NULL,
> + watchdog_get_running, PARAM_FLAG_RO);
> + if (IS_ERR(p))
> + return PTR_ERR(p);
> +
> + p->value = (char *)wd;
> + }
How about adding this parameter unconditionally, with "unknown" as value
when WDOG_HW_RUNNING_SUPPORTED is not set. You can use
dev_add_param_enum() here.
Sascha
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