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 <sboyd@xxxxxxxxxxxxxx>
Cc: Paul Mundt <lethal@xxxxxxxxxxxx>
Cc: Kukjin Kim <kgene.kim@xxxxxxxxxxx>
Cc: David Brown <davidb@xxxxxxxxxxxxxx>
Cc: Tony Lindgren <tony@xxxxxxxxxxx>
Cc: Srinidhi Kasagar <srinidhi.kasagar@xxxxxxxxxxxxxx>
Cc: Linus Walleij <linus.walleij@xxxxxxxxxxxxxx>
---
Changes since V1:
* Pulled up init_cpu_present() to arm/kernel/smp.c instead of
in each platform_smp_prepare_cpus()
arch/arm/kernel/smp.c | 11 +++++++++--
arch/arm/mach-exynos4/platsmp.c | 8 --------
arch/arm/mach-msm/platsmp.c | 8 --------
arch/arm/mach-omap2/omap-smp.c | 8 --------
arch/arm/mach-realview/platsmp.c | 8 --------
arch/arm/mach-shmobile/platsmp.c | 5 -----
arch/arm/mach-tegra/platsmp.c | 8 --------
arch/arm/mach-ux500/platsmp.c | 8 --------
arch/arm/mach-vexpress/ct-ca9x4.c | 4 ----
9 files changed, 9 insertions(+), 59 deletions(-)
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index e7f92a4..167e3cb 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -365,8 +365,7 @@ 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.
@@ -374,6 +373,14 @@ 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
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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