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From: Stephen Boyd <sboyd@codeaurora.org>
To: Lina Iyer <lina.iyer@linaro.org>
Cc: ulf.hansson@linaro.org, khilman@kernel.org, rjw@rjwysocki.net,
	linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	geert@linux-m68k.org, k.kozlowski@samsung.com,
	msivasub@codeaurora.org, agross@codeaurora.org,
	linux-arm-msm@vger.kernel.org, lorenzo.pieralisi@arm.com,
	ahaslam@baylibre.com, mtitinger@baylibre.com
Subject: Re: [RFC v2 07/12] PM / cpu_domains: Add PM Domain governor for CPUs
Date: Tue, 1 Mar 2016 11:35:09 -0800	[thread overview]
Message-ID: <56D5EEED.5060203@codeaurora.org> (raw)
In-Reply-To: <20160301193220.GN1440@linaro.org>

On 03/01/2016 11:32 AM, Lina Iyer wrote:
> On Fri, Feb 26 2016 at 12:33 -0700, Stephen Boyd wrote:
>> On 02/12, Lina Iyer wrote:
>>> @@ -52,6 +55,76 @@ struct cpu_pm_domain *to_cpu_pd(struct
>>> generic_pm_domain *d)
>>>      return res;
>>>  }
>>>
>>> +static bool cpu_pd_down_ok(struct dev_pm_domain *pd)
>>> +{
>>> +    struct generic_pm_domain *genpd = pd_to_genpd(pd);
>>> +    struct cpu_pm_domain *cpu_pd = to_cpu_pd(genpd);
>>> +    int qos = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
>>> +    u64 sleep_ns;
>>> +    ktime_t earliest, next_wakeup;
>>> +    int cpu;
>>> +    int i;
>>> +
>>> +    /* Reset the last set genpd state, default to index 0 */
>>> +    genpd->state_idx = 0;
>>> +
>>> +    /* We dont want to power down, if QoS is 0 */
>>> +    if (!qos)
>>> +        return false;
>>> +
>>> +    /*
>>> +     * Find the sleep time for the cluster.
>>> +     * The time between now and the first wake up of any CPU that
>>> +     * are in this domain hierarchy is the time available for the
>>> +     * domain to be idle.
>>> +     */
>>> +    earliest = ktime_set(KTIME_SEC_MAX, 0);
>>> +    for_each_cpu_and(cpu, cpu_pd->cpus, cpu_online_mask) {
>>
>> We're not worried about hotplug happening in parallel because
>> preemption is disabled here?
>>
> Nope. Hotplug on the same domain or in its hierarchy will be waiting on
> the domain lock to released before becoming online. Any other domain is
> not of concern for this domain governor.
>
> If a core was hotplugged out while this is happening, then we may risk
> making an premature wake up decision, which would happen either way if
> we lock hotplug here.

Ok please make this into a comment in the code.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

WARNING: multiple messages have this Message-ID (diff)
From: sboyd@codeaurora.org (Stephen Boyd)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC v2 07/12] PM / cpu_domains: Add PM Domain governor for CPUs
Date: Tue, 1 Mar 2016 11:35:09 -0800	[thread overview]
Message-ID: <56D5EEED.5060203@codeaurora.org> (raw)
In-Reply-To: <20160301193220.GN1440@linaro.org>

On 03/01/2016 11:32 AM, Lina Iyer wrote:
> On Fri, Feb 26 2016 at 12:33 -0700, Stephen Boyd wrote:
>> On 02/12, Lina Iyer wrote:
>>> @@ -52,6 +55,76 @@ struct cpu_pm_domain *to_cpu_pd(struct
>>> generic_pm_domain *d)
>>>      return res;
>>>  }
>>>
>>> +static bool cpu_pd_down_ok(struct dev_pm_domain *pd)
>>> +{
>>> +    struct generic_pm_domain *genpd = pd_to_genpd(pd);
>>> +    struct cpu_pm_domain *cpu_pd = to_cpu_pd(genpd);
>>> +    int qos = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
>>> +    u64 sleep_ns;
>>> +    ktime_t earliest, next_wakeup;
>>> +    int cpu;
>>> +    int i;
>>> +
>>> +    /* Reset the last set genpd state, default to index 0 */
>>> +    genpd->state_idx = 0;
>>> +
>>> +    /* We dont want to power down, if QoS is 0 */
>>> +    if (!qos)
>>> +        return false;
>>> +
>>> +    /*
>>> +     * Find the sleep time for the cluster.
>>> +     * The time between now and the first wake up of any CPU that
>>> +     * are in this domain hierarchy is the time available for the
>>> +     * domain to be idle.
>>> +     */
>>> +    earliest = ktime_set(KTIME_SEC_MAX, 0);
>>> +    for_each_cpu_and(cpu, cpu_pd->cpus, cpu_online_mask) {
>>
>> We're not worried about hotplug happening in parallel because
>> preemption is disabled here?
>>
> Nope. Hotplug on the same domain or in its hierarchy will be waiting on
> the domain lock to released before becoming online. Any other domain is
> not of concern for this domain governor.
>
> If a core was hotplugged out while this is happening, then we may risk
> making an premature wake up decision, which would happen either way if
> we lock hotplug here.

Ok please make this into a comment in the code.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

  reply	other threads:[~2016-03-01 19:35 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-12 20:50 [RFC v2 00/12] PM: SoC idle support using PM domains Lina Iyer
2016-02-12 20:50 ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 01/12] PM / Domains: Abstract genpd locking Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-26 18:08   ` Stephen Boyd
2016-02-26 18:08     ` Stephen Boyd
2016-03-01 16:55     ` Lina Iyer
2016-03-01 16:55       ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 02/12] PM / Domains: Support IRQ safe PM domains Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-26 18:17   ` Stephen Boyd
2016-02-26 18:17     ` Stephen Boyd
2016-03-01 17:44     ` Lina Iyer
2016-03-01 17:44       ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 03/12] PM / cpu_domains: Setup PM domains for CPUs/clusters Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-17 23:38   ` Lina Iyer
2016-02-17 23:38     ` Lina Iyer
2016-02-18 17:29   ` [BUG FIX] PM / cpu_domains: Check for NULL callbacks Lina Iyer
2016-02-18 17:29     ` Lina Iyer
2016-02-18 17:46     ` Rafael J. Wysocki
2016-02-18 17:46       ` Rafael J. Wysocki
2016-02-18 22:51       ` Lina Iyer
2016-02-18 22:51         ` Lina Iyer
2016-02-26 19:10   ` [RFC v2 03/12] PM / cpu_domains: Setup PM domains for CPUs/clusters Stephen Boyd
2016-02-26 19:10     ` Stephen Boyd
2016-03-01 18:00     ` Lina Iyer
2016-03-01 18:00       ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 04/12] ARM: cpuidle: Add runtime PM support for CPUs Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-26 18:24   ` Stephen Boyd
2016-02-26 18:24     ` Stephen Boyd
2016-03-01 18:36     ` Lina Iyer
2016-03-01 18:36       ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 05/12] timer: Export next wake up of a CPU Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 06/12] PM / cpu_domains: Record CPUs that are part of the domain Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-26 19:20   ` Stephen Boyd
2016-02-26 19:20     ` Stephen Boyd
2016-03-01 19:24     ` Lina Iyer
2016-03-01 19:24       ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 07/12] PM / cpu_domains: Add PM Domain governor for CPUs Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-26 19:33   ` Stephen Boyd
2016-02-26 19:33     ` Stephen Boyd
2016-03-01 19:32     ` Lina Iyer
2016-03-01 19:32       ` Lina Iyer
2016-03-01 19:35       ` Stephen Boyd [this message]
2016-03-01 19:35         ` Stephen Boyd
2016-02-12 20:50 ` [RFC v2 08/12] Documentation / cpu_domains: Describe CPU PM domains setup and governor Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-26 19:43   ` Stephen Boyd
2016-02-26 19:43     ` Stephen Boyd
2016-03-01 19:36     ` Lina Iyer
2016-03-01 19:36       ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 09/12] drivers: firmware: psci: Allow OS Initiated suspend mode Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 10/12] ARM64: psci: Support cluster idle states for OS-Initiated Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 11/12] ARM64: dts: Add PSCI cpuidle support for MSM8916 Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-12 20:50 ` [RFC v2 12/12] ARM64: dts: Define CPU power domain " Lina Iyer
2016-02-12 20:50   ` Lina Iyer
2016-02-26 19:50   ` Stephen Boyd
2016-02-26 19:50     ` Stephen Boyd
2016-03-01 19:41     ` Lina Iyer
2016-03-01 19:41       ` Lina Iyer

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