From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V3 5/5] ARM: tegra20: cpuidle: apply coupled cpuidle for powered-down mode
Date: Fri, 21 Dec 2012 14:06:31 -0700 [thread overview]
Message-ID: <50D4CF57.4030301@wwwdotorg.org> (raw)
In-Reply-To: <1356073828.26029.49.camel@jlo-ubuntu-64.nvidia.com>
On 12/21/2012 12:10 AM, Joseph Lo wrote:
> On Fri, 2012-12-21 at 01:54 +0800, Stephen Warren wrote:
>> On 12/17/2012 07:31 PM, Joseph Lo wrote:
>>> The "powered-down" cpuidle mode of Tegra20 needs the CPU0 be the last one
>>> core to go into this mode before other core. The coupled cpuidle framework
>>> can help to sync the MPCore to coupled state then go into "powered-down"
>>> idle mode together. The driver can just assume the MPCore come into
>>> "powered-down" mode at the same time. No need to take care if the CPU_0
>>> goes into this mode along and only can put it into safe idle mode (WFI).
>>>
>>> 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 for waiting CPU0 in the same state.
>>> When the CPU0 requests powered-down state, it attempts to put the secondary
>>> CPU into reset to prevent it from waking up. Then power down both CPUs
>>> together and power off the cpu rail.
>>>
>>> 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/cpuidle-tegra20.c b/arch/arm/mach-tegra/cpuidle-tegra20.c
>>
>>> +static void tegra20_wake_reset_cpu_1(void)
>>
>> Nit/bikeshe: I think tegra20_wake_from_reset_cpu_1() might be a slightly
>> more descriptive name? I assume the function works on CPU1, which is
>> assumed to be in reset, and removes reset from the CPU so it boots.
>>
> Yes.
> Do you mean this function running on CPU1? It runs on CPU0 to wake up
> CPU1. About the function name, it looks more appropriate.
Sorry for bikeshedding even more, perhaps
tegra20_wake_cpu_1_from_reset(); that makes the word-order better English.
>>> @@ -137,6 +241,9 @@ int __init tegra20_cpuidle_init(void)
>>> for_each_possible_cpu(cpu) {
>>> dev = &per_cpu(tegra_idle_device, cpu);
>>> dev->cpu = cpu;
>>> +#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
>>> + dev->coupled_cpus = *cpu_online_mask;
>>> +#endif
>>
>> That CONFIG option is selected by ARCH_TEGRA_2x_SOC, which must be
>> enabled for this file to be compiled. So, you can drop the ifdef, and
>> make the code uncondtional.
>
> No, I found I need this if I want to make the device works on UP case.
> Then I need to do something like below, when we disable SMP.
>
>> config ARCH_TEGRA_2x_SOC
>> bool "Enable support for Tegra20 family"
>> + select ARCH_NEEDS_CPU_IDLE_COUPLED if SMP
>> select ARCH_REQUIRE_GPIOLIB
>> select ARM_ERRATA_720789
>> select ARM_ERRATA_742230
>
> This will be updated in next version as well.
OK, if the Kconfig looks like that, you're right - the ifdef in the .c
file is needed.
next prev parent reply other threads:[~2012-12-21 21:06 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-18 2:30 [PATCH V3 0/5] ARM: tegra20: cpuidle: add power-down state Joseph Lo
2012-12-18 2:30 ` [PATCH V3 1/5] ARM: tegra: add pending SGI checking API Joseph Lo
2012-12-18 2:42 ` Colin Cross
2012-12-18 2:57 ` Joseph Lo
2012-12-18 10:15 ` Peter De Schrijver
2012-12-18 19:36 ` Colin Cross
2012-12-19 1:06 ` Joseph Lo
2012-12-19 3:47 ` Joseph Lo
2012-12-20 7:16 ` Santosh Shilimkar
2012-12-20 9:34 ` Peter De Schrijver
2012-12-20 9:49 ` Santosh Shilimkar
2012-12-20 9:59 ` Peter De Schrijver
2012-12-20 10:24 ` Santosh Shilimkar
2012-12-20 11:14 ` Peter De Schrijver
2012-12-20 12:06 ` Santosh Shilimkar
2012-12-18 2:30 ` [PATCH V3 2/5] ARM: tegra20: cpuidle: add powered-down state for secondary CPU Joseph Lo
2012-12-18 2:46 ` Colin Cross
2012-12-18 3:06 ` Joseph Lo
2012-12-20 17:43 ` Stephen Warren
2012-12-21 6:36 ` Joseph Lo
2012-12-21 21:04 ` Stephen Warren
2012-12-18 2:30 ` [PATCH V3 3/5] ARM: tegra20: clocks: add CPU low-power function into tegra_cpu_car_ops Joseph Lo
2012-12-20 17:46 ` Stephen Warren
2012-12-21 5:02 ` Joseph Lo
2012-12-21 21:10 ` Stephen Warren
2012-12-18 2:31 ` [PATCH V3 4/5] ARM: tegra20: flowctrl: add support for cpu_suspend_enter/exit Joseph Lo
2012-12-18 2:31 ` [PATCH V3 5/5] ARM: tegra20: cpuidle: apply coupled cpuidle for powered-down mode Joseph Lo
2012-12-18 10:18 ` Peter De Schrijver
2012-12-20 17:54 ` Stephen Warren
2012-12-21 7:10 ` Joseph Lo
2012-12-21 21:06 ` Stephen Warren [this message]
2013-01-02 19:05 ` [PATCH V3 0/5] ARM: tegra20: cpuidle: add power-down state Stephen Warren
2013-01-03 8:39 ` Joseph Lo
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