Re: [PATCH 0/2] OMAP3: wdtimer: fix wdtimer blocking CORE idle

["Cousson, Benoit" <b-cousson@ti.com>]

On 3/10/2011 2:08 PM, Paul Walmsley wrote:
> Hi Benoît,
>
> On Thu, 10 Mar 2011, Cousson, Benoit wrote:
>
>> On 3/10/2011 11:28 AM, kalle.jokiniemi@nokia.com wrote:
>>>
>>>> From: ext Paul Walmsley [mailto:paul@pwsan.com]
>>>> Sent: 10. maaliskuuta 2011 11:50
>>>>
>>>> Thanks Kalle for tracking this down,
>>>>
>>>> could you try this patch along with the patch from this message:
>>>>
>>>>     http://www.spinics.net/lists/linux-omap/msg48115.html
>>
>> I have some question with that patch.
>> By using pm_runtime API, you are suppose to idle the whole IP.
>> In this case, just because you cannot idle a wdt that is running, it works,
>> but the point is that the pm_runtime state will not reflect the HW state.
>> For pm_runtime point of view, the wdt is supposed to be fully idle (both fclk
>> and iclk). Whereas in that case, only the iclk will be gated.
>>
>> Did I miss something?
>
> Looking at it, I don't know how the old driver managed to work at all.
> Commit 7ec5ad0f3c1e28b693185c35f768953c5db32291 ("OMAP: WDT: Use PM
> runtime APIs instead of clk FW APIs") removed this from omap_wdt_probe():
>
> -       /* autogate OCP interface clock */
> -       __raw_writel(0x01, wdev->base + OMAP_WATCHDOG_SYS_CONFIG);
>
> This would put the WDTIMER into force-idle, and nothing ever took it out
> of force-idle.  So I don't quite understand why the PRCM wouldn't just
> turn off the functional clock to the WDTIMER at this point.  Any thoughts
> on this?

The idle definition of the PRCM is just: idle of the ocp clock (iclk). 
The fclk can be active while the module is "idle" for the PRCM point of 
view.
That's why we have a mismatch in that case with the pm_runtime idle 
definition, where the module should be fully idle.

In that case, since the WDT is in the wakeup domain, we do not even have 
to re-enable the iclk since the wakeup domain is always on whenever the 
MPU is running.

That fact that we have to explicitly do a force idle, probably means 
that the autoidle is broken in the IP.

Benoit
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