linux-kernel - Re: [PATCH 1/2] omap: pm34xx: Enable IO / IO-CHAIN wakeups for PER

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Message-ID: <k2w8bb80c381004221622tf623adaw15d72d04a5db5c7e@mail.gmail.com>
Date:	Thu, 22 Apr 2010 16:22:50 -0700
From:	Mike Chan <mike@...roid.com>
To:	Kevin Hilman <khilman@...prootsystems.com>
Cc:	tony@...mide.com, paul@...an.com, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] omap: pm34xx: Enable IO / IO-CHAIN wakeups for PER

On Thu, Apr 22, 2010 at 3:31 PM, Kevin Hilman
<khilman@...prootsystems.com> wrote:
> Mike Chan <mike@...roid.com> writes:
>
>> On Wed, Apr 21, 2010 at 5:07 PM, Kevin Hilman
>> <khilman@...prootsystems.com> wrote:
>>> Mike Chan <mike@...roid.com> writes:
>>>
>>>> IO events can also come from GPIO modules, which reside in the PER domain.
>>>> It is possible for the PER to enter RET while CORE is still in ON.
>>>> If GPIO 2-6 are enabled for IO-pad wakeups, the PER domain will not
>>>> wakeup in this case, unless we enable it.
>>>>
>>>> Signed-off-by: Mike Chan <mike@...roid.com>
>>>
>>> Hi Mike,
>>>
>>> I'm a little puzzled on this one.  My understanding is that the IO pad
>>> is only armed when CORE is in RET or OFF.
>>>
>>
>> The issue we are seeing is when the device is active but idle, if CORE
>> is ON and PER is in RET and the omap is sitting in swfi. If the user
>> presses a keypad button, IO pad doesn't wake us out of idle. Setting a
>> wakeup if PER or CORE goes into RET solve this.
>>
>>> I need to dig a little more in the TRM on this one to clarify.
>>>
>>
>> I was looking at 4.11.2.2 I/O Wake-Up Mechanism (pg 421)
>>
>
> Yeah, that's the right place.
>
> After a little more digging and asking around, this looks like a good
> fix, but there's a minor problem with the implementation:
>
> In the section of the TRM you referenced the following sentence is
> hiding:
>
>  "Software must wait for the I/O daisy chain to complete before it
>   transitions the PER domain to a nonfunctional state."
>
> In the proposed patch, it's likely that PER could transition to
> INACTIVE/RET/OFF before the IO wakeups are enabled.  For example, if
> nothing in PER is active except UART3, then PER will transition to an
> idle state right after omap_uart_prepare_idle(2), which is before
> the IO wakeups are currently enabled.
>
> To be perfectly safe, the IO wakeups should be enabled before PER is
> allowed to transition.
>

Sounds good, I'll spin a v2 and send it out.

-- Mike

> Kevin
>
>
>
>
>
>
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