From 7fa22bd5460bb2021729fa5a1012c60b9b3a56e2 Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Thu, 7 Jul 2011 01:56:51 +0100 Subject: ARM: 6993/1: platsmp: Allow secondary cpu hotplug with maxcpus=1 If an ARM system has multiple cpus in the same socket and the kernel is booted with maxcpus=1, secondary cpus are possible but not present due to how platform_smp_prepare_cpus() is called. Since most typical ARM processors don't actually support physical hotplug, initialize the present map to be equal to the possible map in generic ARM SMP code. Also, always call platform_smp_prepare_cpus() as long as max_cpus is non-zero (0 means no SMP) to allow platform code to do any SMP setup. After applying this patch it's possible to boot an ARM system with maxcpus=1 on the command line and then hotplug in secondary cpus via sysfs. This is more in line with how x86 does things. Signed-off-by: Stephen Boyd Cc: Paul Mundt Cc: Kukjin Kim Cc: David Brown Cc: Tony Lindgren Cc: Srinidhi Kasagar Cc: Linus Walleij Signed-off-by: Russell King diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 344e52b..0ffcf5c 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -361,8 +361,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus) */ if (max_cpus > ncores) max_cpus = ncores; - - if (max_cpus > 1) { + if (ncores > 1 && max_cpus) { /* * Enable the local timer or broadcast device for the * boot CPU, but only if we have more than one CPU. @@ -370,6 +369,14 @@ void __init smp_prepare_cpus(unsigned int max_cpus) percpu_timer_setup(); /* + * Initialise the present map, which describes the set of CPUs + * actually populated at the present time. A platform should + * re-initialize the map in platform_smp_prepare_cpus() if + * present != possible (e.g. physical hotplug). + */ + init_cpu_present(&cpu_possible_map); + + /* * Initialise the SCU if there are more than one CPU * and let them know where to start. */ diff --git a/arch/arm/mach-exynos4/platsmp.c b/arch/arm/mach-exynos4/platsmp.c index c5e65a0..b68d5bd 100644 --- a/arch/arm/mach-exynos4/platsmp.c +++ b/arch/arm/mach-exynos4/platsmp.c @@ -154,14 +154,6 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - - /* - * Initialise the present map, which describes the set of CPUs - * actually populated at the present time. - */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); scu_enable(scu_base_addr()); diff --git a/arch/arm/mach-msm/platsmp.c b/arch/arm/mach-msm/platsmp.c index 2034098..315b9f3 100644 --- a/arch/arm/mach-msm/platsmp.c +++ b/arch/arm/mach-msm/platsmp.c @@ -157,12 +157,4 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - - /* - * Initialise the present map, which describes the set of CPUs - * actually populated at the present time. - */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); } diff --git a/arch/arm/mach-omap2/omap-smp.c b/arch/arm/mach-omap2/omap-smp.c index ecfe93c..ce65e93 100644 --- a/arch/arm/mach-omap2/omap-smp.c +++ b/arch/arm/mach-omap2/omap-smp.c @@ -125,14 +125,6 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - - /* - * Initialise the present map, which describes the set of CPUs - * actually populated at the present time. - */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); /* * Initialise the SCU and wake up the secondary core using diff --git a/arch/arm/mach-realview/platsmp.c b/arch/arm/mach-realview/platsmp.c index 963bf0d..4ae943b 100644 --- a/arch/arm/mach-realview/platsmp.c +++ b/arch/arm/mach-realview/platsmp.c @@ -68,14 +68,6 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - - /* - * Initialise the present map, which describes the set of CPUs - * actually populated at the present time. - */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); scu_enable(scu_base_addr()); diff --git a/arch/arm/mach-shmobile/platsmp.c b/arch/arm/mach-shmobile/platsmp.c index f3888fe..66f9806 100644 --- a/arch/arm/mach-shmobile/platsmp.c +++ b/arch/arm/mach-shmobile/platsmp.c @@ -64,10 +64,5 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); - shmobile_smp_prepare_cpus(); } diff --git a/arch/arm/mach-tegra/platsmp.c b/arch/arm/mach-tegra/platsmp.c index b8ae3c9..1a594dc 100644 --- a/arch/arm/mach-tegra/platsmp.c +++ b/arch/arm/mach-tegra/platsmp.c @@ -129,14 +129,6 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - - /* - * Initialise the present map, which describes the set of CPUs - * actually populated at the present time. - */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); scu_enable(scu_base); } diff --git a/arch/arm/mach-ux500/platsmp.c b/arch/arm/mach-ux500/platsmp.c index 0c527fe..a33df5f 100644 --- a/arch/arm/mach-ux500/platsmp.c +++ b/arch/arm/mach-ux500/platsmp.c @@ -172,14 +172,6 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - - /* - * Initialise the present map, which describes the set of CPUs - * actually populated at the present time. - */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); scu_enable(scu_base_addr()); wakeup_secondary(); diff --git a/arch/arm/mach-vexpress/ct-ca9x4.c b/arch/arm/mach-vexpress/ct-ca9x4.c index 765a71f..bfd32f5 100644 --- a/arch/arm/mach-vexpress/ct-ca9x4.c +++ b/arch/arm/mach-vexpress/ct-ca9x4.c @@ -229,10 +229,6 @@ static void ct_ca9x4_init_cpu_map(void) static void ct_ca9x4_smp_enable(unsigned int max_cpus) { - int i; - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); - scu_enable(MMIO_P2V(A9_MPCORE_SCU)); } #endif -- cgit v0.10.2