Re: [PATCH 2/2] mfd: da9063: fix watchdog ping execution

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Marco,

On 11/4/19 10:44 AM, Marco Felsch wrote:
>> This means that your boot time would increase by 200 ms. If this matter to you,
>> you might want to change this, so watchdog_set_timeout is called only once.
> 
> Increasing the delay isn't a big deal. But after we discussed it again I
> will send a v2 which handles the to fast pings by dropping those.

That would be an option too, but moving watchdog_set_timeout out of boot_entry
would benefit other platforms too.

> 
>> And if you do so, you could drop this patch. The only other places that feed
>> the watchdog are the watchdog poller and the wd command. The watchdog poller
>> already waits 500 ms between pings and the command is meant for debugging/testing.
>> If someone wants to feed the watchdog that fast while testing, why prevent them?
> 
> Becuase if the watchdog gets feeded to fast then the system gets
> reseted. So dropping the patch isn't a option.

If you move watchdog_set_timeout out of boot_entry, you'll only be able to feed the
watchdog too fast if you manually type wd 1; wd 1;, which I argue isn't really an issue
IMHO, but I am fine with what you implement either way.

> 
>> (I assume you don't need to wait 200 ms between ping and disabling WDT, if you do,
>>  one more place is the .priority watchdog device parameter in barebox-next
> 
> Sorry, I don't get this. You don't need to wait 200ms between ping and
> disabling.

Just wanted to make sure that disabling the watchdog twice in rapdi succession doesn't
trigger the issue as well. All good.

Cheers
Ahmad

> 
> Regards,
>   Marco
> 
>> Cheers
>> Ahmad
>>
>>>>>
>>>>> Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
>>>>> ---
>>>>>  drivers/mfd/da9063.c | 11 +++++++++++
>>>>>  1 file changed, 11 insertions(+)
>>>>>
>>>>> diff --git a/drivers/mfd/da9063.c b/drivers/mfd/da9063.c
>>>>> index 4d459c7f18..ab57885240 100644
>>>>> --- a/drivers/mfd/da9063.c
>>>>> +++ b/drivers/mfd/da9063.c
>>>>> @@ -14,6 +14,7 @@
>>>>>   */
>>>>>  
>>>>>  #include <common.h>
>>>>> +#include <clock.h>
>>>>>  #include <driver.h>
>>>>>  #include <gpio.h>
>>>>>  #include <restart.h>
>>>>> @@ -33,6 +34,7 @@ struct da9063 {
>>>>>  	struct i2c_client	*client1;
>>>>>  	struct device_d		*dev;
>>>>>  	unsigned int		timeout;
>>>>> +	uint64_t		last_ping;
>>>>>  };
>>>>>  
>>>>>  /* forbidden/impossible value; timeout will be set to this value initially to
>>>>> @@ -237,6 +239,13 @@ static int da9063_watchdog_ping(struct da9063 *priv)
>>>>>  	int ret;
>>>>>  	u8 val;
>>>>>  
>>>>> +	/* We need to wait at least 200ms till we can resend a ping */
>>>>> +	if (!is_timeout_non_interruptible(priv->last_ping, 200 * MSECOND)) {
>>>>> +		dev_dbg(priv->dev, "active ping delay\n");
>>>>> +		mdelay(50);
>>>>
>>>> I would expect to wait the missing time to 200ms here. Maybe doing
>>>> nothing in this case would be more appropriate here. I mean, why should
>>>> you slow down barebox here when some code triggers the watchdog too
>>>> often?
>>>>
>>>>> +		return da9063_watchdog_ping(priv);
>>>>
>>>> Drop this, just fall through.
>>>
>>> Just prepared a v2 with a busy wait after discussed it with Lucas.
>>> Thanks for your input too :)
>>>
>>> Regards,
>>>   Marco
>>>
>>>> Sascha
>>>>
>>>> -- 
>>>> Pengutronix e.K.                           |                             |
>>>> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
>>>> Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
>>>> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
>>>>
>>>
>>
>> -- 
>> Pengutronix e.K.                           |                             |
>> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
>> Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
>> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
>>
> 


-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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