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 <sboyd@codeaurora.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: David Brown <davidb@codeaurora.org>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Cc: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 0 insertions, 4 deletions

diff --git a/arch/arm/mach-vexpress/ct-ca9x4.c b/arch/arm/mach-vexpress/ct-ca9x4.c
index 765a71ff7f3b..bfd32f52c2db 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