Re: [PATCH v10 5/5] Watchdog: ARM SBSA Generic Watchdog half timeout panic support

[Fu Wei]

On 7 February 2016 at 02:57, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> On 02/06/2016 10:02 AM, Fu Wei wrote:
>>
>> Hi Guenter,
>>
>> On 6 February 2016 at 07:54, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>>>
>>> On 02/05/2016 10:21 AM, Fu Wei wrote:
>>>>
>>>>
>>>> On 5 February 2016 at 22:42, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>>>>>
>>>>>
>>>>> On 02/05/2016 01:51 AM, Fu Wei wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> Hi Guenter,
>>>>>>
>>>>>> On 4 February 2016 at 13:17, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 02/03/2016 03:00 PM, Fu Wei wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On 4 February 2016 at 02:45, Timur Tabi <timur@xxxxxxxxxxxxxx>
>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Fu Wei wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> As you know I have made the pre-timeout support patch, If people
>>>>>>>>>> like
>>>>>>>>>> it, i am happy to go on upstream it separately.
>>>>>>>>>>
>>>>>>>>>> If we want to use pre-timeout here, user only can use
>>>>>>>>>> get_pretimeout
>>>>>>>>>> and disable panic by setting pretimeout to 0
>>>>>>>>>> but user can not really set pretimeout, because "pre-timeout  ==
>>>>>>>>>> timeout / 2 (always)".
>>>>>>>>>> if user want to change pretimeout, he/she has to set_time instead.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Ok, I think patches 4 and 5 should be combined, and I think the
>>>>>>>>> Kconfig
>>>>>>>>> entry should be removed and just use panic_enabled.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Agreed.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> np, will do
>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> NP, will update this patchset like that ,  thanks :-)
>>>>>>>>
>>>>>>>
>>>>>>> Also, if panic is enabled, the timeout needs to be adjusted
>>>>>>> accordingly
>>>>>>> (to only panic after the entire timeout period has expired, not after
>>>>>>> half of it). We can not panic the system after timeout / 2.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> OK, my thought is
>>>>>>
>>>>>> if panic is enabled :
>>>>>> |--------WOR-------WS0--------WOR-------WS1
>>>>>> |------timeout------(panic)------timeout-----reset
>>>>>>
>>>>>> if panic is disabled .
>>>>>> |--------WOR-------WS0--------WOR-------WS1
>>>>>> |---------------------timeout---------------------reset
>>>>>>
>>>>>>     panic_enabled only can be configured when module is loaded by
>>>>>> module
>>>>>> parameter
>>>>>>
>>>>>> But user should know that max_timeout(panic_enable) =
>>>>>> max_timeout(panic_disable) / 2
>>>>>>
>>>>>
>>>>> That means you'll have to update max_timeout accordingly.
>>>>
>>>>
>>>>
>>>> panic_enabled only can be configured when module is loaded, so we
>>>> don't need to update it.
>>>>
>>>> max_timeout will only be set up in the init stage.
>>>>
>>>> Does it make sense ? :-)
>>>>
>>> Not sure I understand your problem or question.
>>>
>>> max_timeout will have to reflect the correct maximum timeout, under
>>> all circumstances. It will have to be set to the correct value before
>>> the watchdog driver is registered.
>>
>>
>> yes, understood,  my thought is :
>>
>> in  static int sbsa_gwdt_probe(struct platform_device *pdev)
>>
>> if (action) {
>>          wdd->min_timeout = 1;
>>          wdd->max_timeout = U32_MAX / gwdt->clk;
>> } else {
>>          wdd->min_timeout = 2;
>>          wdd->max_timeout = U32_MAX / gwdt->clk * 2;
>
>
> Pretty much, though you would also have to adjust all calculations
> using gwdt->clk, in both set_timeout() and get_timeout(). Wonder if
> you could adjust gwdt->clk instead.
>
> Does min_timeout really have to be 2 if panic is disabled ?
> The only reason seems to be the calculation in sbsa_gwdt_set_timeout().
>
>         writel(timeout / 2 * gwdt->clk, gwdt->control_base + SBSA_GWDT_WOR);
>
> Maybe you could use something like
>
>         writel(timeout * (gwdt->clk / 2), ...);
>
> instead. Or, as mentioned above, adjust the value of gwdt->clk
> to include the factor.

yes,  Thanks for pointing it out.
I will fix that following your suggestion.

>
> Thanks,
> Guenter
>



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch
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