linux-kernel - Re: [PATCH] ARM: tegra20: Store CPU "resettable" status in IRAM

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Message-ID: <54BE8868.2080101@gmail.com>
Date:	Tue, 20 Jan 2015 19:55:04 +0300
From:	Dmitry Osipenko <digetx@...il.com>
To:	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>
CC:	Alexandre Courbot <gnurou@...il.com>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] ARM: tegra20: Store CPU "resettable" status in IRAM

19.01.2015 21:26, Dmitry Osipenko пишет:
> 19.01.2015 21:00, Dmitry Osipenko пишет:
>> 19.01.2015 20:45, Stephen Warren пишет:
>>> On 01/19/2015 10:41 AM, Dmitry Osipenko wrote:
>>>> 19.01.2015 20:26, Stephen Warren пишет:
>>>>> Hopefully this works out. I suppose it's unlikely anyone will be
>>>>> running code on
>>>>> the AVP upstrem, so any potential conflict with AVP's usage of IRAM
>>>>> isn't likely
>>>>> to occur.
>>>>>
>>>> I don't see how it can conflict with AVP code. First KB of IRAM is
>>>> reserved for reset handler. Am I missing something?
>>>>
>>>>  From reset.h:
>>>>
>>>> /* The first 1K of IRAM is permanently reserved for the CPU reset
>>>> handler */
>>>
>>> I believe "CPU" in that context means AVP CPU. Still, I may not be correct, and
>>> to be honest it's likely not too well defined even if that comment seems
>>> clear-cut.
>>>
>> Hmm... Suddenly I recalled that LP2 was always disabled in downstream kernel. I
>> remember that I tried it once (couple years ago) and it didn't work, however I
>> presume it was just broken. Now I don't feel good with it.
>>
> Can't generic RAM be used for "resettable" status? Or it will be too slow?...
>
> CPU1 always come up after CPU0, so RAM is already init'ed. Given that CPU0 can't
> be halted with running CPU1, I suppose CPU1 can't be booted first, right? Anyway
> it's not the case for linux.
>
Correcting myself:

Well, it's meaningless in case if LP2 cpuidle can't co-exist with AVP firmware. 
Isn't possible verify it?

-- 
Dmitry
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