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Message-ID: <7e1a02f5-4c15-0a90-ba8e-cbfbb59da23c@intel.com>
Date: Tue, 7 Nov 2017 01:51:02 +0100
From: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-kernel@...r.kernel.org
Cc: stable@...r.kernel.org,
Reinette Chatre <reinette.chatre@...el.com>,
Alex Shi <alex.shi@...aro.org>
Subject: Re: [PATCH 4.13 09/36] PM / QoS: Fix device resume latency PM QoS
On 11/6/2017 10:12 AM, Greg Kroah-Hartman wrote:
> 4.13-stable review patch. If anyone has any objections, please let me know.
Please drop this from the -stable queue, it has been reverted from the
mainline.
Thanks,
Rafael
> ------------------
>
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> commit 0cc2b4e5a020fc7f4d1795741c116c983e9467d7 upstream.
>
> The special value of 0 for device resume latency PM QoS means
> "no restriction", but there are two problems with that.
>
> First, device resume latency PM QoS requests with 0 as the
> value are always put in front of requests with positive
> values in the priority lists used internally by the PM QoS
> framework, causing 0 to be chosen as an effective constraint
> value. However, that 0 is then interpreted as "no restriction"
> effectively overriding the other requests with specific
> restrictions which is incorrect.
>
> Second, the users of device resume latency PM QoS have no
> way to specify that *any* resume latency at all should be
> avoided, which is an artificial limitation in general.
>
> To address these issues, modify device resume latency PM QoS to
> use S32_MAX as the "no constraint" value and 0 as the "no
> latency at all" one and rework its users (the cpuidle menu
> governor, the genpd QoS governor and the runtime PM framework)
> to follow these changes.
>
> Also add a special "n/a" value to the corresponding user space I/F
> to allow user space to indicate that it cannot accept any resume
> latencies at all for the given device.
>
> Fixes: 85dc0b8a4019 (PM / QoS: Make it possible to expose PM QoS latency constraints)
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=197323
> Reported-by: Reinette Chatre <reinette.chatre@...el.com>
> Tested-by: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Acked-by: Alex Shi <alex.shi@...aro.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> ---
> Documentation/ABI/testing/sysfs-devices-power | 4 +
> drivers/base/cpu.c | 3 -
> drivers/base/power/domain_governor.c | 53 ++++++++++++++------------
> drivers/base/power/qos.c | 2
> drivers/base/power/runtime.c | 2
> drivers/base/power/sysfs.c | 25 ++++++++++--
> drivers/cpuidle/governors/menu.c | 4 -
> include/linux/pm_qos.h | 5 +-
> 8 files changed, 63 insertions(+), 35 deletions(-)
>
> --- a/Documentation/ABI/testing/sysfs-devices-power
> +++ b/Documentation/ABI/testing/sysfs-devices-power
> @@ -211,7 +211,9 @@ Description:
> device, after it has been suspended at run time, from a resume
> request to the moment the device will be ready to process I/O,
> in microseconds. If it is equal to 0, however, this means that
> - the PM QoS resume latency may be arbitrary.
> + the PM QoS resume latency may be arbitrary and the special value
> + "n/a" means that user space cannot accept any resume latency at
> + all for the given device.
>
> Not all drivers support this attribute. If it isn't supported,
> it is not present.
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -377,7 +377,8 @@ int register_cpu(struct cpu *cpu, int nu
>
> per_cpu(cpu_sys_devices, num) = &cpu->dev;
> register_cpu_under_node(num, cpu_to_node(num));
> - dev_pm_qos_expose_latency_limit(&cpu->dev, 0);
> + dev_pm_qos_expose_latency_limit(&cpu->dev,
> + PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
>
> return 0;
> }
> --- a/drivers/base/power/domain_governor.c
> +++ b/drivers/base/power/domain_governor.c
> @@ -14,23 +14,20 @@
> static int dev_update_qos_constraint(struct device *dev, void *data)
> {
> s64 *constraint_ns_p = data;
> - s32 constraint_ns = -1;
> + s64 constraint_ns = -1;
>
> if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
> constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
>
> - if (constraint_ns < 0) {
> + if (constraint_ns < 0)
> constraint_ns = dev_pm_qos_read_value(dev);
> - constraint_ns *= NSEC_PER_USEC;
> - }
> - if (constraint_ns == 0)
> +
> + if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
> return 0;
>
> - /*
> - * constraint_ns cannot be negative here, because the device has been
> - * suspended.
> - */
> - if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
> + constraint_ns *= NSEC_PER_USEC;
> +
> + if (constraint_ns < *constraint_ns_p || *constraint_ns_p < 0)
> *constraint_ns_p = constraint_ns;
>
> return 0;
> @@ -63,10 +60,14 @@ static bool default_suspend_ok(struct de
>
> spin_unlock_irqrestore(&dev->power.lock, flags);
>
> - if (constraint_ns < 0)
> + if (constraint_ns == 0)
> return false;
>
> - constraint_ns *= NSEC_PER_USEC;
> + if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
> + constraint_ns = -1;
> + else
> + constraint_ns *= NSEC_PER_USEC;
> +
> /*
> * We can walk the children without any additional locking, because
> * they all have been suspended at this point and their
> @@ -76,14 +77,19 @@ static bool default_suspend_ok(struct de
> device_for_each_child(dev, &constraint_ns,
> dev_update_qos_constraint);
>
> - if (constraint_ns > 0) {
> - constraint_ns -= td->suspend_latency_ns +
> - td->resume_latency_ns;
> - if (constraint_ns == 0)
> - return false;
> + if (constraint_ns < 0) {
> + /* The children have no constraints. */
> + td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
> + td->cached_suspend_ok = true;
> + } else {
> + constraint_ns -= td->suspend_latency_ns + td->resume_latency_ns;
> + if (constraint_ns > 0) {
> + td->effective_constraint_ns = constraint_ns;
> + td->cached_suspend_ok = true;
> + } else {
> + td->effective_constraint_ns = 0;
> + }
> }
> - td->effective_constraint_ns = constraint_ns;
> - td->cached_suspend_ok = constraint_ns >= 0;
>
> /*
> * The children have been suspended already, so we don't need to take
> @@ -145,13 +151,14 @@ static bool __default_power_down_ok(stru
> td = &to_gpd_data(pdd)->td;
> constraint_ns = td->effective_constraint_ns;
> /* default_suspend_ok() need not be called before us. */
> - if (constraint_ns < 0) {
> + if (constraint_ns < 0)
> constraint_ns = dev_pm_qos_read_value(pdd->dev);
> - constraint_ns *= NSEC_PER_USEC;
> - }
> - if (constraint_ns == 0)
> +
> + if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
> continue;
>
> + constraint_ns *= NSEC_PER_USEC;
> +
> /*
> * constraint_ns cannot be negative here, because the device has
> * been suspended.
> --- a/drivers/base/power/qos.c
> +++ b/drivers/base/power/qos.c
> @@ -189,7 +189,7 @@ static int dev_pm_qos_constraints_alloca
> plist_head_init(&c->list);
> c->target_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE;
> c->default_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE;
> - c->no_constraint_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE;
> + c->no_constraint_value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
> c->type = PM_QOS_MIN;
> c->notifiers = n;
>
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -253,7 +253,7 @@ static int rpm_check_suspend_allowed(str
> || (dev->power.request_pending
> && dev->power.request == RPM_REQ_RESUME))
> retval = -EAGAIN;
> - else if (__dev_pm_qos_read_value(dev) < 0)
> + else if (__dev_pm_qos_read_value(dev) == 0)
> retval = -EPERM;
> else if (dev->power.runtime_status == RPM_SUSPENDED)
> retval = 1;
> --- a/drivers/base/power/sysfs.c
> +++ b/drivers/base/power/sysfs.c
> @@ -218,7 +218,14 @@ static ssize_t pm_qos_resume_latency_sho
> struct device_attribute *attr,
> char *buf)
> {
> - return sprintf(buf, "%d\n", dev_pm_qos_requested_resume_latency(dev));
> + s32 value = dev_pm_qos_requested_resume_latency(dev);
> +
> + if (value == 0)
> + return sprintf(buf, "n/a\n");
> + else if (value == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
> + value = 0;
> +
> + return sprintf(buf, "%d\n", value);
> }
>
> static ssize_t pm_qos_resume_latency_store(struct device *dev,
> @@ -228,11 +235,21 @@ static ssize_t pm_qos_resume_latency_sto
> s32 value;
> int ret;
>
> - if (kstrtos32(buf, 0, &value))
> - return -EINVAL;
> + if (!kstrtos32(buf, 0, &value)) {
> + /*
> + * Prevent users from writing negative or "no constraint" values
> + * directly.
> + */
> + if (value < 0 || value == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
> + return -EINVAL;
>
> - if (value < 0)
> + if (value == 0)
> + value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
> + } else if (!strcmp(buf, "n/a") || !strcmp(buf, "n/a\n")) {
> + value = 0;
> + } else {
> return -EINVAL;
> + }
>
> ret = dev_pm_qos_update_request(dev->power.qos->resume_latency_req,
> value);
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -298,8 +298,8 @@ static int menu_select(struct cpuidle_dr
> data->needs_update = 0;
> }
>
> - /* resume_latency is 0 means no restriction */
> - if (resume_latency && resume_latency < latency_req)
> + if (resume_latency < latency_req &&
> + resume_latency != PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
> latency_req = resume_latency;
>
> /* Special case when user has set very strict latency requirement */
> --- a/include/linux/pm_qos.h
> +++ b/include/linux/pm_qos.h
> @@ -27,16 +27,17 @@ enum pm_qos_flags_status {
> PM_QOS_FLAGS_ALL,
> };
>
> -#define PM_QOS_DEFAULT_VALUE -1
> +#define PM_QOS_DEFAULT_VALUE (-1)
> +#define PM_QOS_LATENCY_ANY S32_MAX
>
> #define PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE (2000 * USEC_PER_SEC)
> #define PM_QOS_NETWORK_LAT_DEFAULT_VALUE (2000 * USEC_PER_SEC)
> #define PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE 0
> #define PM_QOS_MEMORY_BANDWIDTH_DEFAULT_VALUE 0
> #define PM_QOS_RESUME_LATENCY_DEFAULT_VALUE 0
> +#define PM_QOS_RESUME_LATENCY_NO_CONSTRAINT PM_QOS_LATENCY_ANY
> #define PM_QOS_LATENCY_TOLERANCE_DEFAULT_VALUE 0
> #define PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT (-1)
> -#define PM_QOS_LATENCY_ANY ((s32)(~(__u32)0 >> 1))
>
> #define PM_QOS_FLAG_NO_POWER_OFF (1 << 0)
> #define PM_QOS_FLAG_REMOTE_WAKEUP (1 << 1)
>
>
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