On 6/25/20 1:32 AM, Tero Kristo wrote:
> On 24/06/2020 18:24, Jan Kiszka wrote:
>> On 24.06.20 13:45, Tero Kristo wrote:
>>> If the RTI watchdog has been started by someone (like bootloader) when
>>> the driver probes, we must adjust the initial ping timeout to match the
>>> currently running watchdog window to avoid generating watchdog reset.
>>>
>>> Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
>>> ---
>>> drivers/watchdog/rti_wdt.c | 25 +++++++++++++++++++++++++
>>> 1 file changed, 25 insertions(+)
>>>
>>> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
>>> index d456dd72d99a..02ea2b2435f5 100644
>>> --- a/drivers/watchdog/rti_wdt.c
>>> +++ b/drivers/watchdog/rti_wdt.c
>>> @@ -55,11 +55,13 @@ static int heartbeat;
>>> * @base - base io address of WD device
>>> * @freq - source clock frequency of WDT
>>> * @wdd - hold watchdog device as is in WDT core
>>> + * @min_hw_heartbeat_save - save of the min hw heartbeat value
>>> */
>>> struct rti_wdt_device {
>>> void __iomem *base;
>>> unsigned long freq;
>>> struct watchdog_device wdd;
>>> + unsigned int min_hw_heartbeat_save;
>>> };
>>> static int rti_wdt_start(struct watchdog_device *wdd)
>>> @@ -107,6 +109,11 @@ static int rti_wdt_ping(struct watchdog_device *wdd)
>>> /* put watchdog in active state */
>>> writel_relaxed(WDKEY_SEQ1, wdt->base + RTIWDKEY);
>>> + if (wdt->min_hw_heartbeat_save) {
>>> + wdd->min_hw_heartbeat_ms = wdt->min_hw_heartbeat_save;
>>> + wdt->min_hw_heartbeat_save = 0;
>>> + }
>>> +
>>> return 0;
>>> }
>>> @@ -201,6 +208,24 @@ static int rti_wdt_probe(struct platform_device *pdev)
>>> goto err_iomap;
>>> }
>>> + if (readl(wdt->base + RTIDWDCTRL) == WDENABLE_KEY) {
>>> + u32 time_left;
>>> + u32 heartbeat;
>>> +
>>> + set_bit(WDOG_HW_RUNNING, &wdd->status);
>>> + time_left = rti_wdt_get_timeleft(wdd);
>>> + heartbeat = readl(wdt->base + RTIDWDPRLD);
>>> + heartbeat <<= WDT_PRELOAD_SHIFT;
>>> + heartbeat /= wdt->freq;
>>> + if (time_left < heartbeat / 2)
>>> + wdd->min_hw_heartbeat_ms = 0;
>>> + else
>>> + wdd->min_hw_heartbeat_ms =
>>> + (time_left - heartbeat / 2 + 1) * 1000;
>>> +
>>> + wdt->min_hw_heartbeat_save = 11 * heartbeat * 1000 / 20;
>>> + }
>>> +
>>> ret = watchdog_register_device(wdd);
>>> if (ret) {
>>> dev_err(dev, "cannot register watchdog device\n");
>>>
>>
>> This assumes that the bootloader also programmed a 50% window, right? The pending U-Boot patch will do that, but what if that may chance or someone uses a different setup?
>
> Yes, we assume 50%. I think based on the hw design, 50% is the only sane value to be used, otherwise you just shrink the open window too much and for no apparent reason.
>
Not sure if that is a valid assumption. Someone who designs a watchdog
with such a narrow ping window might as well also use it. The question
is if you want to rely on that assumption, or check and change it if needed.
Also, I wonder if we should add an API function such as
"set_last_hw_keepalive()" to avoid all that complexity.
Thanks,
Guenter
