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(h-178-174-189-39.A498.priv.bahnhof.se. [178.174.189.39]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-32fa29134d4sm21136211fa.22.2025.07.16.05.33.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Jul 2025 05:33:44 -0700 (PDT) From: Ulf Hansson To: "Rafael J . Wysocki" , linux-pm@vger.kernel.org Cc: Kevin Hilman , Pavel Machek , Len Brown , Daniel Lezcano , Saravana Kannan , Maulik Shah , Prasad Sodagudi , Ulf Hansson , linux-kernel@vger.kernel.org Subject: [RFC/PATCH 1/3] PM: QoS: Introduce a system-wakeup QoS limit Date: Wed, 16 Jul 2025 14:33:17 +0200 Message-ID: <20250716123323.65441-2-ulf.hansson@linaro.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250716123323.65441-1-ulf.hansson@linaro.org> References: <20250716123323.65441-1-ulf.hansson@linaro.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Some platforms and devices supports multiple low-power-states than can be used for system-wide suspend. Today these states are selected on per subsystem basis and in most cases it's the deepest possible state that becomes selected. For some use-cases this is a problem as it isn't suitable or even breaks the system-wakeup latency constraint, when we decide to enter these deeper states during system-wide suspend. Therefore, let's introduce an interface for user-space, allowing us to specify the system-wakeup QoS limit. Subsequent changes will start taking into account the QoS limit. Signed-off-by: Ulf Hansson --- include/linux/pm_qos.h | 9 ++++ kernel/power/qos.c | 114 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 123 insertions(+) diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h index 4a69d4af3ff8..5f84084f19c8 100644 --- a/include/linux/pm_qos.h +++ b/include/linux/pm_qos.h @@ -143,6 +143,15 @@ bool pm_qos_update_flags(struct pm_qos_flags *pqf, struct pm_qos_flags_request *req, enum pm_qos_req_action action, s32 val); =20 +#ifdef CONFIG_PM_SLEEP +s32 system_wakeup_latency_qos_limit(void); +#else +static inline s32 system_wakeup_latency_qos_limit(void) +{ + return PM_QOS_RESUME_LATENCY_NO_CONSTRAINT; +} +#endif + #ifdef CONFIG_CPU_IDLE s32 cpu_latency_qos_limit(void); bool cpu_latency_qos_request_active(struct pm_qos_request *req); diff --git a/kernel/power/qos.c b/kernel/power/qos.c index 4244b069442e..fb496c220ffe 100644 --- a/kernel/power/qos.c +++ b/kernel/power/qos.c @@ -209,6 +209,120 @@ bool pm_qos_update_flags(struct pm_qos_flags *pqf, return prev_value !=3D curr_value; } =20 +#ifdef CONFIG_PM_SLEEP +static struct pm_qos_constraints system_wakeup_latency_constraints =3D { + .list =3D PLIST_HEAD_INIT(system_wakeup_latency_constraints.list), + .target_value =3D PM_QOS_RESUME_LATENCY_NO_CONSTRAINT, + .default_value =3D PM_QOS_RESUME_LATENCY_NO_CONSTRAINT, + .no_constraint_value =3D PM_QOS_RESUME_LATENCY_NO_CONSTRAINT, + .type =3D PM_QOS_MIN, +}; + +/** + * system_wakeup_latency_qos_limit - Current system wakeup latency QoS lim= it. + * + * Returns the current system wakeup latency QoS limit that may have been + * requested by user-space. + */ +s32 system_wakeup_latency_qos_limit(void) +{ + return pm_qos_read_value(&system_wakeup_latency_constraints); +} + +static int system_wakeup_latency_qos_open(struct inode *inode, + struct file *filp) +{ + struct pm_qos_request *req; + + req =3D kzalloc(sizeof(*req), GFP_KERNEL); + if (!req) + return -ENOMEM; + + req->qos =3D &system_wakeup_latency_constraints; + pm_qos_update_target(req->qos, &req->node, PM_QOS_ADD_REQ, + PM_QOS_RESUME_LATENCY_NO_CONSTRAINT); + filp->private_data =3D req; + + return 0; +} + +static int system_wakeup_latency_qos_release(struct inode *inode, + struct file *filp) +{ + struct pm_qos_request *req =3D filp->private_data; + + filp->private_data =3D NULL; + pm_qos_update_target(req->qos, &req->node, PM_QOS_REMOVE_REQ, + PM_QOS_RESUME_LATENCY_NO_CONSTRAINT); + kfree(req); + + return 0; +} + +static ssize_t system_wakeup_latency_qos_read(struct file *filp, + char __user *buf, + size_t count, + loff_t *f_pos) +{ + s32 value =3D pm_qos_read_value(&system_wakeup_latency_constraints); + + return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32)); +} + +static ssize_t system_wakeup_latency_qos_write(struct file *filp, + const char __user *buf, + size_t count, loff_t *f_pos) +{ + struct pm_qos_request *req =3D filp->private_data; + s32 value; + + if (count =3D=3D sizeof(s32)) { + if (copy_from_user(&value, buf, sizeof(s32))) + return -EFAULT; + } else { + int ret; + + ret =3D kstrtos32_from_user(buf, count, 16, &value); + if (ret) + return ret; + } + + if (value < 0) + return -EINVAL; + + pm_qos_update_target(req->qos, &req->node, PM_QOS_UPDATE_REQ, value); + + return count; +} + +static const struct file_operations system_wakeup_latency_qos_fops =3D { + .open =3D system_wakeup_latency_qos_open, + .release =3D system_wakeup_latency_qos_release, + .read =3D system_wakeup_latency_qos_read, + .write =3D system_wakeup_latency_qos_write, + .llseek =3D noop_llseek, +}; + +static struct miscdevice system_wakeup_latency_qos_miscdev =3D { + .minor =3D MISC_DYNAMIC_MINOR, + .name =3D "system_wakeup_latency", + .fops =3D &system_wakeup_latency_qos_fops, +}; + +static int __init system_wakeup_latency_qos_init(void) +{ + int ret; + + ret =3D misc_register(&system_wakeup_latency_qos_miscdev); + if (ret < 0) + pr_err("%s: %s setup failed\n", __func__, + system_wakeup_latency_qos_miscdev.name); + + return ret; +} +late_initcall(system_wakeup_latency_qos_init); +#endif /* CONFIG_PM_SLEEP */ + #ifdef CONFIG_CPU_IDLE /* Definitions related to the CPU latency QoS. */ =20 --=20 2.43.0