Really sorry for this mail and previous noisy mails; my thunderbird
client must be misconfigured to send out mail for command + s shortcut
when I wanted to save draft...
Heyi
On 2025/2/19 11:40, Heyi Guo wrote:
Hi Guenter,
Thanks for your comments.
On 2025/2/18 13:33, Guenter Roeck wrote:
> On 2/17/25 19:16, Heyi Guo wrote:
>> Aspeed watchdog uses counting down logic, so the value set to register
>> should be the value of subtracting pretimeout from total timeout.
>>
>> Fixes: 9ec0b7e06835 ("watchdog: aspeed: Enable pre-timeout interrupt")
>>
>> Signed-off-by: Heyi Guo <guoheyi@xxxxxxxxxxxxxxxxx>
>>
>> Cc: Wim Van Sebroeck <wim@xxxxxxxxxxxxxxxxxx>
>> Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
>> Cc: Joel Stanley <joel@xxxxxxxxx>
>> Cc: Andrew Jeffery <andrew@xxxxxxxxxxxxxxxxxxxx>
>> Cc: Eddie James <eajames@xxxxxxxxxxxxx>
>> ---
>> drivers/watchdog/aspeed_wdt.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/watchdog/aspeed_wdt.c b/drivers/watchdog/aspeed_wdt.c
>> index b4773a6aaf8c..520d8aba12a5 100644
>> --- a/drivers/watchdog/aspeed_wdt.c
>> +++ b/drivers/watchdog/aspeed_wdt.c
>> @@ -187,6 +187,13 @@ static int aspeed_wdt_set_pretimeout(struct
>> watchdog_device *wdd,
>> u32 actual = pretimeout * WDT_RATE_1MHZ;
>> u32 s = wdt->cfg->irq_shift;
>> u32 m = wdt->cfg->irq_mask;
>> + u32 reload = readl(wdt->base + WDT_RELOAD_VALUE);
>> +
>
> It is unusual to use a register value here and not the configured timeout
> value. I would have assumed that pretimeout is compared against wdt->timout,
> not against the register value, and that the multiplication with WDT_RATE_1MHZ
> is done after validation. This needs an explanation.
It was supposed to be a straight-forward way to check if the pretimeout value is
supported by the hardware. I can change to wdt->timeout if it is better.
Further, in the case of wdt->timeout > max_hw_heartbeat_ms, shall we restrict
the pretimeout to be larger than wdt->timeout - max_hw_heartbeat_ms / 2? For
the watchdog_kworker works in max_hw_heartbeat_ms / 2 interval, pretimeout
event may be triggered unexpected when watchdog is not pinged in
(max_hw_heartbeat_ms - (timeout - pretimeout)).
>
>> + if (actual >= reload)
>> + return -EINVAL;
>> +
>
> On top of that, you'll also need to explain why watchdog_pretimeout_invalid()
> and with it the validation in watchdog_set_pretimeout() does not work for this
> watchdog and why this extra validation is necessary.
watchdog_pretimeout_invalid() will return false if wdt->timeout == 0, but we
can't determine the hardware pretimeout value if timeout == 0 here.
>
> Guenter
>
>> + /* watchdog timer is counting down */
>> + actual = reload - actual;
>> wdd->pretimeout = pretimeout;
>> wdt->ctrl &= ~m;
