From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752058AbdJXLo4 (ORCPT ); Tue, 24 Oct 2017 07:44:56 -0400 Received: from cloudserver094114.home.net.pl ([79.96.170.134]:61213 "EHLO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751825AbdJXLow (ORCPT ); Tue, 24 Oct 2017 07:44:52 -0400 From: "Rafael J. Wysocki" To: Linux PM Cc: "Rafael J. Wysocki" , ramesh.thomas@intel.com, LKML , Reinette Chatre , Alex Shi , Ulf Hansson Subject: [PATCH v2] PM / QoS: Fix device resume latency PM QoS Date: Tue, 24 Oct 2017 13:35:05 +0200 Message-ID: <1948004.bU45lK7TsE@aspire.rjw.lan> In-Reply-To: References: <2245486.jYtPfSLF5g@aspire.rjw.lan> <2465945.6cfLQGiipl@aspire.rjw.lan> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rafael J. Wysocki 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 Tested-by: Reinette Chatre Signed-off-by: Rafael J. Wysocki Acked-by: Alex Shi --- -> v2: Add a missing "else" branch in pm_qos_resume_latency_store(). --- 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(-) Index: linux-pm/drivers/base/power/sysfs.c =================================================================== --- linux-pm.orig/drivers/base/power/sysfs.c +++ linux-pm/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); Index: linux-pm/include/linux/pm_qos.h =================================================================== --- linux-pm.orig/include/linux/pm_qos.h +++ linux-pm/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) Index: linux-pm/drivers/cpuidle/governors/menu.c =================================================================== --- linux-pm.orig/drivers/cpuidle/governors/menu.c +++ linux-pm/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 */ Index: linux-pm/drivers/base/power/domain_governor.c =================================================================== --- linux-pm.orig/drivers/base/power/domain_governor.c +++ linux-pm/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. Index: linux-pm/drivers/base/power/runtime.c =================================================================== --- linux-pm.orig/drivers/base/power/runtime.c +++ linux-pm/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; Index: linux-pm/drivers/base/cpu.c =================================================================== --- linux-pm.orig/drivers/base/cpu.c +++ linux-pm/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; } Index: linux-pm/drivers/base/power/qos.c =================================================================== --- linux-pm.orig/drivers/base/power/qos.c +++ linux-pm/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; Index: linux-pm/Documentation/ABI/testing/sysfs-devices-power =================================================================== --- linux-pm.orig/Documentation/ABI/testing/sysfs-devices-power +++ linux-pm/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.