Hi Guenter,


On 10 June 2015 at 11:41, Fu Wei [off-list ref] wrote:

Hi Guenter,

On 10 June 2015 at 00:45, Guenter Roeck [off-list ref] wrote:

quoted

On 06/09/2015 09:29 AM, Timur Tabi wrote:

quoted

On 06/09/2015 11:22 AM, Guenter Roeck wrote:

quoted

but I see your point. Essentially, the specification is broken
for all practical purposes, since, as you point out, enabling
the watchdog overwrites and explicitly sets WCV. Effectively
this means that just using WCV to program the timeout period
is not really possible.

I am not really sure how to address this. We can either only use WOR,
and forget about pretimeout, or we can enforce a minimum pretimeout.
In the latter case, we'll have to write WCV after writing WOR.

In talking with our hardware engineers, using WCV to program the timeout
period is not a valid operation.  This is why I keep arguing against the
pre-timeout feature, and I don't agree that servers should always use
pre-timeout.

Not sure if "not valid" is correct - after all, it is mentioned in the
specification. However, it is at the very least fragile.

I think we should focus on SBSA spec, but not a specific chip design,
because this is SBSA watchdog, not a driver for an IP core from a
specific chip vendor.
this operation is mentioned in the spec,
and I have tested my driver on Foundation model(from ARM) and a real hardware.

quoted

I tend to agree that we should just forget about pretimeout and
use your original approach, where the timeout value is used
to program WOR. Everything else is really just asking for trouble.

I don't mind if we give up pretimeout, The reason I use pretimeout is:
this concept matches the function of two stage timeouts.

but, If we give up pretimeout, could you give me a suggestion:

How to config the two stage timeouts
(1)from enabling watchdog to WS0
(2)the time from WS1 to WS0

If we only have one timeout parameter,  How to config the two stage timeouts?
Any suggestion ?

I have another thought for this, please allow me to sent anther
patchset in a day. see if you like it.

If we make the first stage timeout is timeout/2,  this violates the
definition of timeout.
I don't think users expect interrupt, panic or reboot at timeout/2.

And WS1  definitely isn't a backup of WS0.

quoted

Guenter

--
Best regards,

Fu Wei
Software Engineer
Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch
Ph: +86 21 61221326(direct)
Ph: +86 186 2020 4684 (mobile)
Room 1512, Regus One Corporate Avenue,Level 15,
One Corporate Avenue,222 Hubin Road,Huangpu District,
Shanghai,China 200021

-- 
Best regards,

Fu Wei
Software Engineer
Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch
Ph: +86 21 61221326(direct)
Ph: +86 186 2020 4684 (mobile)
Room 1512, Regus One Corporate Avenue,Level 15,
One Corporate Avenue,222 Hubin Road,Huangpu District,
Shanghai,China 200021
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