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[24.201.245.36]) by mx.google.com with ESMTP id i7si5237393qcu.54.2013.07.22.20.31.46 for ; Mon, 22 Jul 2013 20:31:46 -0700 (PDT) Received-SPF: neutral (google.com: 24.201.245.36 is neither permitted nor denied by best guess record for domain of nicolas.pitre@linaro.org) client-ip=24.201.245.36; Received: from yoda.home ([70.83.209.44]) by VL-VM-MR004.ip.videotron.ca (Oracle Communications Messaging Exchange Server 7u4-22.01 64bit (built Apr 21 2011)) with ESMTP id <0MQD009EADSV4940@VL-VM-MR004.ip.videotron.ca>; Mon, 22 Jul 2013 23:31:44 -0400 (EDT) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 073B32DA0511; Mon, 22 Jul 2013 23:31:44 -0400 (EDT) From: Nicolas Pitre To: linux-arm-kernel@lists.infradead.org Cc: dave.martin@linaro.org, lorenzo.pieralisi@arm.com, patches@linaro.org Subject: [PATCH 09/13] ARM: bL_switcher: ability to enable and disable the switcher via sysfs Date: Mon, 22 Jul 2013 23:31:25 -0400 Message-id: <1374550289-25305-10-git-send-email-nicolas.pitre@linaro.org> X-Mailer: git-send-email 1.8.1.2 In-reply-to: <1374550289-25305-1-git-send-email-nicolas.pitre@linaro.org> References: <1374550289-25305-1-git-send-email-nicolas.pitre@linaro.org> X-Gm-Message-State: ALoCoQkJtOEwMxyEiyWYT25VAsPB2THgrRzsZ+RTWoUUK5q6veXfJWxVieWJcpDIuGwWyx94FMvz X-Original-Sender: nicolas.pitre@linaro.org X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 209.85.212.53 is neither permitted nor denied by best guess record for domain of patch+caf_=patchwork-forward=linaro.org@linaro.org) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Precedence: list Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org List-ID: X-Google-Group-Id: 836684582541 List-Post: , List-Help: , List-Archive: List-Unsubscribe: , Content-transfer-encoding: 7BIT The /sys/kernel/bL_switcher/enable file allows to enable or disable the switcher by writing 1 or 0 to it respectively. It is still enabled by default on boot. Signed-off-by: Nicolas Pitre --- arch/arm/common/bL_switcher.c | 171 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 160 insertions(+), 11 deletions(-) diff --git a/arch/arm/common/bL_switcher.c b/arch/arm/common/bL_switcher.c index 34eff3bc25..abeeff5520 100644 --- a/arch/arm/common/bL_switcher.c +++ b/arch/arm/common/bL_switcher.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #include @@ -226,6 +227,7 @@ struct bL_thread { struct task_struct *task; wait_queue_head_t wq; int wanted_cluster; + struct completion started; }; static struct bL_thread bL_threads[MAX_CPUS_PER_CLUSTER]; @@ -237,6 +239,7 @@ static int bL_switcher_thread(void *arg) int cluster; sched_setscheduler_nocheck(current, SCHED_FIFO, ¶m); + complete(&t->started); do { if (signal_pending(current)) @@ -252,7 +255,7 @@ static int bL_switcher_thread(void *arg) return 0; } -static struct task_struct * __init bL_switcher_thread_create(int cpu, void *arg) +static struct task_struct *bL_switcher_thread_create(int cpu, void *arg) { struct task_struct *task; @@ -301,9 +304,11 @@ EXPORT_SYMBOL_GPL(bL_switch_request); * Activation and configuration code. */ +static unsigned int bL_switcher_active; +static unsigned int bL_switcher_cpu_original_cluster[MAX_CPUS_PER_CLUSTER]; static cpumask_t bL_switcher_removed_logical_cpus; -static void __init bL_switcher_restore_cpus(void) +static void bL_switcher_restore_cpus(void) { int i; @@ -311,7 +316,7 @@ static void __init bL_switcher_restore_cpus(void) cpu_up(i); } -static int __init bL_switcher_halve_cpus(void) +static int bL_switcher_halve_cpus(void) { int cpu, cluster, i, ret; cpumask_t cluster_mask[2], common_mask; @@ -355,8 +360,10 @@ static int __init bL_switcher_halve_cpus(void) * is equal to their physical CPU number. This is * not perfect but good enough for now. */ - if (cpu == i) + if (cpu == i) { + bL_switcher_cpu_original_cluster[cpu] = cluster; continue; + } } ret = cpu_down(i); @@ -370,18 +377,18 @@ static int __init bL_switcher_halve_cpus(void) return 0; } -static int __init bL_switcher_init(void) +static int bL_switcher_enable(void) { int cpu, ret; - pr_info("big.LITTLE switcher initializing\n"); - - if (MAX_NR_CLUSTERS != 2) { - pr_err("%s: only dual cluster systems are supported\n", __func__); - return -EINVAL; + cpu_hotplug_driver_lock(); + if (bL_switcher_active) { + cpu_hotplug_driver_unlock(); + return 0; } - cpu_hotplug_driver_lock(); + pr_info("big.LITTLE switcher initializing\n"); + ret = bL_switcher_halve_cpus(); if (ret) { cpu_hotplug_driver_unlock(); @@ -391,13 +398,155 @@ static int __init bL_switcher_init(void) for_each_online_cpu(cpu) { struct bL_thread *t = &bL_threads[cpu]; init_waitqueue_head(&t->wq); + init_completion(&t->started); t->wanted_cluster = -1; t->task = bL_switcher_thread_create(cpu, t); } + + bL_switcher_active = 1; cpu_hotplug_driver_unlock(); pr_info("big.LITTLE switcher initialized\n"); return 0; } +#ifdef CONFIG_SYSFS + +static void bL_switcher_disable(void) +{ + unsigned int cpu, cluster, i; + struct bL_thread *t; + struct task_struct *task; + + cpu_hotplug_driver_lock(); + if (!bL_switcher_active) { + cpu_hotplug_driver_unlock(); + return; + } + bL_switcher_active = 0; + + /* + * To deactivate the switcher, we must shut down the switcher + * threads to prevent any other requests from being accepted. + * Then, if the final cluster for given logical CPU is not the + * same as the original one, we'll recreate a switcher thread + * just for the purpose of switching the CPU back without any + * possibility for interference from external requests. + */ + for_each_online_cpu(cpu) { + BUG_ON(cpu != (cpu_logical_map(cpu) & 0xff)); + t = &bL_threads[cpu]; + task = t->task; + t->task = NULL; + if (!task || IS_ERR(task)) + continue; + kthread_stop(task); + /* no more switch may happen on this CPU at this point */ + cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1); + if (cluster == bL_switcher_cpu_original_cluster[cpu]) + continue; + init_completion(&t->started); + t->wanted_cluster = bL_switcher_cpu_original_cluster[cpu]; + task = bL_switcher_thread_create(cpu, t); + if (!IS_ERR(task)) { + wait_for_completion(&t->started); + kthread_stop(task); + cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1); + if (cluster == bL_switcher_cpu_original_cluster[cpu]) + continue; + } + /* If execution gets here, we're in trouble. */ + pr_crit("%s: unable to restore original cluster for CPU %d\n", + __func__, cpu); + for_each_cpu(i, &bL_switcher_removed_logical_cpus) { + if ((cpu_logical_map(i) & 0xff) != cpu) + continue; + pr_crit("%s: CPU %d can't be restored\n", + __func__, i); + cpumask_clear_cpu(i, &bL_switcher_removed_logical_cpus); + break; + } + } + + bL_switcher_restore_cpus(); + cpu_hotplug_driver_unlock(); +} + +static ssize_t bL_switcher_active_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%u\n", bL_switcher_active); +} + +static ssize_t bL_switcher_active_store(struct kobject *kobj, + struct kobj_attribute *attr, const char *buf, size_t count) +{ + int ret; + + switch (buf[0]) { + case '0': + bL_switcher_disable(); + ret = 0; + break; + case '1': + ret = bL_switcher_enable(); + break; + default: + ret = -EINVAL; + } + + return (ret >= 0) ? count : ret; +} + +static struct kobj_attribute bL_switcher_active_attr = + __ATTR(active, 0644, bL_switcher_active_show, bL_switcher_active_store); + +static struct attribute *bL_switcher_attrs[] = { + &bL_switcher_active_attr.attr, + NULL, +}; + +static struct attribute_group bL_switcher_attr_group = { + .attrs = bL_switcher_attrs, +}; + +static struct kobject *bL_switcher_kobj; + +static int __init bL_switcher_sysfs_init(void) +{ + int ret; + + bL_switcher_kobj = kobject_create_and_add("bL_switcher", kernel_kobj); + if (!bL_switcher_kobj) + return -ENOMEM; + ret = sysfs_create_group(bL_switcher_kobj, &bL_switcher_attr_group); + if (ret) + kobject_put(bL_switcher_kobj); + return ret; +} + +#endif /* CONFIG_SYSFS */ + +static int __init bL_switcher_init(void) +{ + int ret; + + if (MAX_NR_CLUSTERS != 2) { + pr_err("%s: only dual cluster systems are supported\n", __func__); + return -EINVAL; + } + + ret = bL_switcher_enable(); + if (ret) + return ret; + +#ifdef CONFIG_SYSFS + ret = bL_switcher_sysfs_init(); + if (ret) + pr_err("%s: unable to create sysfs entry\n", __func__); +#endif + + return 0; +} + late_initcall(bL_switcher_init);