linux-kernel - [PATCH] ARM: npcm: Add CPU hotplug callbacks for kexec support

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Date:   Wed,  1 Nov 2023 17:24:53 -0700
From:   william@...nnington.com
To:     tmaimon77@...il.com, tali.perry1@...il.com, avifishman70@...il.com
Cc:     linux-arm-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
        openbmc@...ts.ozlabs.org, Brian Ma <chma0@...oton.com>,
        "William A . Kennington III" <william@...nnington.com>
Subject: [PATCH] ARM: npcm: Add CPU hotplug callbacks for kexec support

From: Brian Ma <chma0@...oton.com>

Add callbacks required for kexec to function. The NPCM7xx/NPCN8xx does
not expose controls for powering down CPU cores, so just wait in idle
loop.

Signed-off-by: Brian Ma <chma0@...oton.com>
Signed-off-by: William A. Kennington III <william@...nnington.com>
---
 arch/arm/mach-npcm/platsmp.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/arm/mach-npcm/platsmp.c b/arch/arm/mach-npcm/platsmp.c
index 41891d3aa124..6cc7b5894f08 100644
--- a/arch/arm/mach-npcm/platsmp.c
+++ b/arch/arm/mach-npcm/platsmp.c
@@ -69,10 +69,27 @@ static void __init npcm7xx_smp_prepare_cpus(unsigned int max_cpus)
 
 	iounmap(scu_base);
 }
+#ifdef CONFIG_HOTPLUG_CPU
+static void npcm7xx_cpu_die(unsigned int cpu)
+{
+	while (1)
+		cpu_do_idle();
+}
+
+static int npcm7xx_cpu_kill(unsigned int l_cpu)
+{
+	return 1;
+}
+#endif
+
 
 static struct smp_operations npcm7xx_smp_ops __initdata = {
 	.smp_prepare_cpus = npcm7xx_smp_prepare_cpus,
 	.smp_boot_secondary = npcm7xx_smp_boot_secondary,
+#ifdef CONFIG_HOTPLUG_CPU
+	.cpu_die			= npcm7xx_cpu_die,
+	.cpu_kill			= npcm7xx_cpu_kill,
+#endif
 };
 
 CPU_METHOD_OF_DECLARE(npcm7xx_smp, "nuvoton,npcm750-smp", &npcm7xx_smp_ops);
-- 
2.42.0.820.g83a721a137-goog