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SubjectRe: [PATCHv2 4/5] watchdog: rti-wdt: attach to running watchdog during probe
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On 05/07/2020 18:07, Guenter Roeck wrote:
> On 7/3/20 5:04 AM, Tero Kristo wrote:
>> If the RTI watchdog is running already during probe, the driver must
>> configure itself to match the HW. Window size and timeout is probed from
>> hardware, and the last keepalive ping is adjusted to match it also.
>>
>> Signed-off-by: Tero Kristo <t-kristo@ti.com>
>> ---
>> drivers/watchdog/rti_wdt.c | 26 +++++++++++++++++++++++---
>> 1 file changed, 23 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
>> index 110bfc8d0bb3..987e5a798cb4 100644
>> --- a/drivers/watchdog/rti_wdt.c
>> +++ b/drivers/watchdog/rti_wdt.c
>> @@ -213,6 +213,7 @@ static int rti_wdt_probe(struct platform_device *pdev)
>> struct watchdog_device *wdd;
>> struct rti_wdt_device *wdt;
>> struct clk *clk;
>> + u32 last_ping = 0;
>>
>> wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
>> if (!wdt)
>> @@ -258,11 +259,8 @@ static int rti_wdt_probe(struct platform_device *pdev)
>> wdd->min_timeout = 1;
>> wdd->max_hw_heartbeat_ms = (WDT_PRELOAD_MAX << WDT_PRELOAD_SHIFT) /
>> wdt->freq * 1000;
>> - wdd->timeout = DEFAULT_HEARTBEAT;
>
> What if the watchdog is not running ?

Configuring wdd->timeout seems redundant, it gets set by the
watchdog_init_timeout call done later. I just moved that post the check
for a running watchdog so that the same call is used for both cases.

>
>> wdd->parent = dev;
>>
>> - watchdog_init_timeout(wdd, heartbeat, dev);
>> -
>> watchdog_set_drvdata(wdd, wdt);
>> watchdog_set_nowayout(wdd, 1);
>> watchdog_set_restart_priority(wdd, 128);
>> @@ -274,12 +272,34 @@ static int rti_wdt_probe(struct platform_device *pdev)
>> goto err_iomap;
>> }
>>
>> + if (readl(wdt->base + RTIDWDCTRL) == WDENABLE_KEY) {
>> + u32 time_left;
>> +
>> + 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;
>> +
>
> This ignores any heartbeat configured as module parameter, which most
> people will consider unexpected. It might be worthwhile documenting that.

I'll add a dev_warn for this case.

>
>> + wsize = readl(wdt->base + RTIWWDSIZECTRL);
>> + ret = rti_wdt_setup_hw_hb(wdd);
>> + if (ret)
>> + goto err_iomap;
>> +
>> + last_ping = -(time_left - heartbeat) * 1000;
>
> Why the double negation ?
>
> last_ping = (heartbeat - time_left) * 1000;
>
> seems simpler. Also, what if heartbeat - time_left is negative for whatever
> reason ?

Will fix. I'll add a dev_warn for that case and assume last ping to be zero.

>
> I am not sure if it is a good idea to call rti_wdt_get_timeleft()
> here. It might be better to add a helper function such as
> rti_wdt_get_timeleft_ms() to return the time left in milli-seconds
> for improved accuracy.

Will add that.

-Tero

>
>> + }
>> +
>> + watchdog_init_timeout(wdd, heartbeat, dev);
>> +
>> ret = watchdog_register_device(wdd);
>> if (ret) {
>> dev_err(dev, "cannot register watchdog device\n");
>> goto err_iomap;
>> }
>>
>> + if (last_ping)
>> + watchdog_set_last_hw_keepalive(wdd, last_ping);
>> +
>> return 0;
>>
>> err_iomap:
>>
>

--
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