Hi,
On 11/5/19 11:40 AM, Sascha Hauer wrote:
> 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().
Ye, board code can use watchdog_hw_running added in this patch.
Hush scripts can use the device parameter. I'll amend the commit message.
> 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.
Ok.
>
>> @@ -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.
Sounds good.
>
> Sascha
>
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