diff options
| -rw-r--r-- | arch/arm/mm/cache-b15-rac.c | 91 | ||||
| -rw-r--r-- | include/linux/cpuhotplug.h | 2 |
2 files changed, 93 insertions, 0 deletions
diff --git a/arch/arm/mm/cache-b15-rac.c b/arch/arm/mm/cache-b15-rac.c index 679d44f003fd..d85b63211759 100644 --- a/arch/arm/mm/cache-b15-rac.c +++ b/arch/arm/mm/cache-b15-rac.c @@ -13,6 +13,8 @@ #include <linux/io.h> #include <linux/bitops.h> #include <linux/of_address.h> +#include <linux/notifier.h> +#include <linux/cpu.h> #include <asm/cacheflush.h> #include <asm/hardware/cache-b15-rac.h> @@ -42,6 +44,7 @@ extern void v7_flush_kern_cache_all(void); static void __iomem *b15_rac_base; static DEFINE_SPINLOCK(rac_lock); +static u32 rac_config0_reg; /* Initialization flag to avoid checking for b15_rac_base, and to prevent * multi-platform kernels from crashing here as well. @@ -137,6 +140,74 @@ static void b15_rac_enable(void) __b15_rac_enable(enable); } +#ifdef CONFIG_HOTPLUG_CPU +/* The CPU hotplug case is the most interesting one, we basically need to make + * sure that the RAC is disabled for the entire system prior to having a CPU + * die, in particular prior to this dying CPU having exited the coherency + * domain. + * + * Once this CPU is marked dead, we can safely re-enable the RAC for the + * remaining CPUs in the system which are still online. + * + * Offlining a CPU is the problematic case, onlining a CPU is not much of an + * issue since the CPU and its cache-level hierarchy will start filling with + * the RAC disabled, so L1 and L2 only. + * + * In this function, we should NOT have to verify any unsafe setting/condition + * b15_rac_base: + * + * It is protected by the RAC_ENABLED flag which is cleared by default, and + * being cleared when initial procedure is done. b15_rac_base had been set at + * that time. + * + * RAC_ENABLED: + * There is a small timing windows, in b15_rac_init(), between + * cpuhp_setup_state_*() + * ... + * set RAC_ENABLED + * However, there is no hotplug activity based on the Linux booting procedure. + * + * Since we have to disable RAC for all cores, we keep RAC on as long as as + * possible (disable it as late as possible) to gain the cache benefit. + * + * Thus, dying/dead states are chosen here + * + * We are choosing not do disable the RAC on a per-CPU basis, here, if we did + * we would want to consider disabling it as early as possible to benefit the + * other active CPUs. + */ + +/* Running on the dying CPU */ +static int b15_rac_dying_cpu(unsigned int cpu) +{ + spin_lock(&rac_lock); + + /* Indicate that we are starting a hotplug procedure */ + __clear_bit(RAC_ENABLED, &b15_rac_flags); + + /* Disable the readahead cache and save its value to a global */ + rac_config0_reg = b15_rac_disable_and_flush(); + + spin_unlock(&rac_lock); + + return 0; +} + +/* Running on a non-dying CPU */ +static int b15_rac_dead_cpu(unsigned int cpu) +{ + spin_lock(&rac_lock); + + /* And enable it */ + __b15_rac_enable(rac_config0_reg); + __set_bit(RAC_ENABLED, &b15_rac_flags); + + spin_unlock(&rac_lock); + + return 0; +} +#endif /* CONFIG_HOTPLUG_CPU */ + static int __init b15_rac_init(void) { struct device_node *dn; @@ -157,6 +228,20 @@ static int __init b15_rac_init(void) goto out; } +#ifdef CONFIG_HOTPLUG_CPU + ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DEAD, + "arm/cache-b15-rac:dead", + NULL, b15_rac_dead_cpu); + if (ret) + goto out_unmap; + + ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DYING, + "arm/cache-b15-rac:dying", + NULL, b15_rac_dying_cpu); + if (ret) + goto out_cpu_dead; +#endif + spin_lock(&rac_lock); reg = __raw_readl(b15_rac_base + RAC_CONFIG0_REG); for_each_possible_cpu(cpu) @@ -170,6 +255,12 @@ static int __init b15_rac_init(void) pr_info("Broadcom Brahma-B15 readahead cache at: 0x%p\n", b15_rac_base + RAC_CONFIG0_REG); + goto out; + +out_cpu_dead: + cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CACHE_B15_RAC_DYING); +out_unmap: + iounmap(b15_rac_base); out: of_node_put(dn); return ret; diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 201ab7267986..3f7b30fcc96a 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -59,6 +59,7 @@ enum cpuhp_state { CPUHP_PCI_XGENE_DEAD, CPUHP_IOMMU_INTEL_DEAD, CPUHP_LUSTRE_CFS_DEAD, + CPUHP_AP_ARM_CACHE_B15_RAC_DEAD, CPUHP_WORKQUEUE_PREP, CPUHP_POWER_NUMA_PREPARE, CPUHP_HRTIMERS_PREPARE, @@ -137,6 +138,7 @@ enum cpuhp_state { CPUHP_AP_ARM64_ISNDEP_STARTING, CPUHP_AP_SMPCFD_DYING, CPUHP_AP_X86_TBOOT_DYING, + CPUHP_AP_ARM_CACHE_B15_RAC_DYING, CPUHP_AP_ONLINE, CPUHP_TEARDOWN_CPU, CPUHP_AP_ONLINE_IDLE, |