Re: [GIT PULL] MSM fix

From: Arnd Bergmann
Date: Thu Jul 21 2011 - 10:49:54 EST

On Thursday 21 July 2011, Russell King - ARM Linux wrote:
> > It looks like it would apply to 2.6.38 and 39 as well. I'm not sure
> > it qualifies under the "It must fix a real bug that bothers people".
> > It would only apply if someone had set NR_CPUS to more than 2.
> Err, this makes no sense. MSM doesn't have a get_core_count function
> and as far as I can see never has done in mainline.

I've committed the version below now, with a clarified title.
The patch looks reasonable to me, but there may be some issue
I'm missing of course. The other platforms that used to have
a get_core_count function no longer have that because you changed
them to use scu_get_core_count, but that doesn't seem to apply
to mach-msm.

I did not add a stable tag though.


Subject: [PATCH] ARM: msm: platsmp: determine number of CPU cores at boot time

Previously we just assumed there were CONFIG_NR_CPUS cpus present in
the system. Instead, figure out the number of cpus from the MIDR

Signed-off-by: Jeff Ohlstein <johlstei@xxxxxxxxxxxxxx>
Signed-off-by: David Brown <davidb@xxxxxxxxxxxxxx>
[arnd: clarified patch title]
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

diff --git a/arch/arm/mach-msm/platsmp.c b/arch/arm/mach-msm/platsmp.c
index 2034098..5ba77d0 100644
--- a/arch/arm/mach-msm/platsmp.c
+++ b/arch/arm/mach-msm/platsmp.c
@@ -18,6 +18,7 @@

#include <asm/hardware/gic.h>
#include <asm/cacheflush.h>
+#include <asm/cputype.h>
#include <asm/mach-types.h>

#include <mach/msm_iomap.h>
@@ -40,6 +41,12 @@ volatile int pen_release = -1;

static DEFINE_SPINLOCK(boot_lock);

+static inline int get_core_count(void)
+ /* 1 + the PART[1:0] field of MIDR */
+ return ((read_cpuid_id() >> 4) & 3) + 1;
void __cpuinit platform_secondary_init(unsigned int cpu)
/* Configure edge-triggered PPIs */
@@ -147,9 +154,9 @@ int __cpuinit boot_secondary(unsigned int cpu, struct task_struct *idle)
void __init smp_init_cpus(void)
- unsigned int i;
+ unsigned int i, ncores = get_core_count();

- for (i = 0; i < NR_CPUS; i++)
+ for (i = 0; i < ncores; i++)
set_cpu_possible(i, true);

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