linux-kernel - [PATCH v2 1/2] powerpc: export the CPU node count

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Date:   Thu, 10 Nov 2022 19:06:18 +0100
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/2] powerpc: export the CPU node count

At boot time, the FDT is parsed to compute the number of CPUs.
In addition count the number of CPU nodes and export it.

This is useful when building the FDT for a kexeced kernel since we need to
take in account the CPU node added since the boot time during CPU hotplug
operations.

Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
---
 arch/powerpc/include/asm/prom.h | 1 +
 arch/powerpc/kernel/prom.c      | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/powerpc/include/asm/prom.h b/arch/powerpc/include/asm/prom.h
index 2e82820fbd64..c0107d8ddd8c 100644
--- a/arch/powerpc/include/asm/prom.h
+++ b/arch/powerpc/include/asm/prom.h
@@ -85,6 +85,7 @@ struct of_drc_info {
 extern int of_read_drc_info_cell(struct property **prop,
 			const __be32 **curval, struct of_drc_info *data);
 
+extern unsigned int boot_cpu_node_count;
 
 /*
  * There are two methods for telling firmware what our capabilities are.
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 1eed87d954ba..645f4450dfc3 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -72,6 +72,7 @@ int __initdata iommu_is_off;
 int __initdata iommu_force_on;
 unsigned long tce_alloc_start, tce_alloc_end;
 u64 ppc64_rma_size;
+unsigned int boot_cpu_node_count __ro_after_init;
 #endif
 static phys_addr_t first_memblock_size;
 static int __initdata boot_cpu_count;
@@ -335,6 +336,8 @@ static int __init early_init_dt_scan_cpus(unsigned long node,
 	if (type == NULL || strcmp(type, "cpu") != 0)
 		return 0;
 
+	boot_cpu_node_count++;
+
 	/* Get physical cpuid */
 	intserv = of_get_flat_dt_prop(node, "ibm,ppc-interrupt-server#s", &len);
 	if (!intserv)
-- 
2.38.1