From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V2 2/6] ARM: tegra20: cpuidle: add powered-down state for secondary CPU
Date: Thu, 06 Dec 2012 11:59:05 -0700 [thread overview]
Message-ID: <50C0EAF9.1080807@wwwdotorg.org> (raw)
In-Reply-To: <1354778576.13857.19.camel@jlo-ubuntu-64.nvidia.com>
On 12/06/2012 12:22 AM, Joseph Lo wrote:
> On Thu, 2012-12-06 at 06:18 +0800, Stephen Warren wrote:
>> On 12/05/2012 03:01 AM, Joseph Lo wrote:
>>> The powered-down state of Tegra20 requires power gating both CPU cores.
>>> When the secondary CPU requests to enter powered-down state, it saves
>>> its own contexts and then enters WFI. The Tegra20 had a limition to
>>> power down both CPU cores. The secondary CPU must waits for CPU0 in
>>> powered-down state too. If the secondary CPU be woken up before CPU0
>>> entering powered-down state, then it needs to restore its CPU states
>>> and waits for next chance.
>>>
>>> Be aware of that, you may see the legacy power state "LP2" in the code
>>> which is exactly the same meaning of "CPU power down".
>>> diff --git a/arch/arm/mach-tegra/sleep-tegra20.S b/arch/arm/mach-tegra/sleep-tegra20.S
>>
>>> +/*
>>> + * tegra_pen_lock
>>
>>> + * on cpu 0:
>>> + * SCRATCH38 = r2 = flag[0]
>>> + * SCRATCH39 = r3 = flag[1]
>>
>> It would be slightly clearer if that was written:
>>
>> * r2 = flag[0] (in SCRATCH38)
>> * r3 = flag[1] (in SCRATCH39)
>>
>> since the meaning of r2/r3 is what's being selected.
>>
> OK. Will fix.
>
>>> + mov r12, #1
>>> + str r12, [r2] @ flag[cpu] = 1
So here I can see we should hard-code the value that's written
>>> + dsb
>>> + str r12, [r1] @ !turn = cpu
But here we're also writing "1" always, whereas the comment says it's
writing "cpu", and given the algorithm description, I would expect to
write "cpu" here not "1".
>> Should that be "str r0, [r1]"? Otherwise, you're always writing 1 there,
>> not writing the CPU ID as expected.
>
> The CPU_ID was not used to lock or un-lock the flag. Wriging 1 to lock
> and 0 to release.
next prev parent reply other threads:[~2012-12-06 18:59 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-05 10:01 [PATCH V2 0/6] ARM: tegra20: cpuidle: add power-down state Joseph Lo
2012-12-05 10:01 ` [PATCH V2 1/6] ARM: tegra: add pending SGI checking API Joseph Lo
2012-12-05 22:09 ` Stephen Warren
2012-12-06 7:04 ` Joseph Lo
2012-12-06 18:52 ` Stephen Warren
2012-12-05 10:01 ` [PATCH V2 2/6] ARM: tegra20: cpuidle: add powered-down state for secondary CPU Joseph Lo
2012-12-05 10:50 ` Lorenzo Pieralisi
2012-12-06 8:25 ` Joseph Lo
2012-12-06 18:56 ` Stephen Warren
2013-01-11 7:20 ` Joseph Lo
2013-01-11 12:24 ` Lorenzo Pieralisi
2013-01-15 3:00 ` Joseph Lo
2013-01-15 11:34 ` Lorenzo Pieralisi
2013-01-16 3:17 ` Joseph Lo
2013-01-12 17:33 ` Nicolas Pitre
2012-12-05 22:18 ` Stephen Warren
2012-12-06 7:22 ` Joseph Lo
2012-12-06 18:59 ` Stephen Warren [this message]
2012-12-05 10:01 ` [PATCH V2 3/6] ARM: tegra20: clocks: add CPU low-power function into tegra_cpu_car_ops Joseph Lo
2012-12-05 10:01 ` [PATCH V2 4/6] ARM: tegra20: flowctrl: add support for cpu_suspend_enter/exit Joseph Lo
2012-12-05 10:01 ` [PATCH V2 5/6] ARM: tegra20: cpuidle: add powered-down state for CPU0 Joseph Lo
2012-12-05 10:01 ` [PATCH V2 6/6] ARM: tegra20: cpuidle: apply coupled cpuidle for powered-down mode Joseph Lo
2012-12-05 10:01 ` Joseph Lo
2012-12-05 10:10 ` Joseph Lo
2012-12-06 11:03 ` Grant Likely
2012-12-05 10:01 ` Joseph Lo
2012-12-05 10:11 ` Joseph Lo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=50C0EAF9.1080807@wwwdotorg.org \
--to=swarren@wwwdotorg$(echo .)org \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox