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Subject[PATCH 4.14 180/496] ARC: setup cpu possible mask according to possible-cpus dts property
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>

[ Upstream commit a29a25275452c97fe35815f1eb9564f2a07a1965 ]

As we have option in u-boot to set CPU mask for running linux,
we want to pass information to kernel about CPU cores should
be brought up. So we patch kernel dtb in u-boot to set
possible-cpus property.

This also allows us to have correctly setuped MCIP debug mask.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arc/kernel/smp.c | 50 ++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 40 insertions(+), 10 deletions(-)

--- a/arch/arc/kernel/smp.c
+++ b/arch/arc/kernel/smp.c
@@ -24,6 +24,7 @@
#include <linux/reboot.h>
#include <linux/irqdomain.h>
#include <linux/export.h>
+#include <linux/of_fdt.h>

#include <asm/processor.h>
#include <asm/setup.h>
@@ -47,6 +48,42 @@ void __init smp_prepare_boot_cpu(void)
{
}

+static int __init arc_get_cpu_map(const char *name, struct cpumask *cpumask)
+{
+ unsigned long dt_root = of_get_flat_dt_root();
+ const char *buf;
+
+ buf = of_get_flat_dt_prop(dt_root, name, NULL);
+ if (!buf)
+ return -EINVAL;
+
+ if (cpulist_parse(buf, cpumask))
+ return -EINVAL;
+
+ return 0;
+}
+
+/*
+ * Read from DeviceTree and setup cpu possible mask. If there is no
+ * "possible-cpus" property in DeviceTree pretend all [0..NR_CPUS-1] exist.
+ */
+static void __init arc_init_cpu_possible(void)
+{
+ struct cpumask cpumask;
+
+ if (arc_get_cpu_map("possible-cpus", &cpumask)) {
+ pr_warn("Failed to get possible-cpus from dtb, pretending all %u cpus exist\n",
+ NR_CPUS);
+
+ cpumask_setall(&cpumask);
+ }
+
+ if (!cpumask_test_cpu(0, &cpumask))
+ panic("Master cpu (cpu[0]) is missed in cpu possible mask!");
+
+ init_cpu_possible(&cpumask);
+}
+
/*
* Called from setup_arch() before calling setup_processor()
*
@@ -58,10 +95,7 @@ void __init smp_prepare_boot_cpu(void)
*/
void __init smp_init_cpus(void)
{
- unsigned int i;
-
- for (i = 0; i < NR_CPUS; i++)
- set_cpu_possible(i, true);
+ arc_init_cpu_possible();

if (plat_smp_ops.init_early_smp)
plat_smp_ops.init_early_smp();
@@ -70,16 +104,12 @@ void __init smp_init_cpus(void)
/* called from init ( ) => process 1 */
void __init smp_prepare_cpus(unsigned int max_cpus)
{
- int i;
-
/*
* if platform didn't set the present map already, do it now
* boot cpu is set to present already by init/main.c
*/
- if (num_present_cpus() <= 1) {
- for (i = 0; i < max_cpus; i++)
- set_cpu_present(i, true);
- }
+ if (num_present_cpus() <= 1)
+ init_cpu_present(cpu_possible_mask);
}

void __init smp_cpus_done(unsigned int max_cpus)

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