Re: [PATCH linux-next tag: next-20210322] ARM: aspeed: Add CPU hotplug callbacks for kexec support

On 3/22/2021 09:40, Bruce Mitchell wrote:

On 3/22/2021 08:57, Bruce Mitchell wrote:

quoted

These callbacks are required for kexec to function. The AST2600 does not
expose any controls for powering down it's CPU cores, so we borrow the
approach taken from socfpga and wait in the idle loop.

Author: Joel Stanley [off-list ref]

Signed-off-by: Bruce Mitchell <redacted>
---
  arch/arm/mach-aspeed/platsmp.c | 20 ++++++++++++++++++++
  1 file changed, 20 insertions(+)

diff --git a/arch/arm/mach-aspeed/platsmp.c 

b/arch/arm/mach-aspeed/platsmp.c
index 2324becf7991..1ae3ff5a9701 100644

--- a/arch/arm/mach-aspeed/platsmp.c
+++ b/arch/arm/mach-aspeed/platsmp.c

@@ -7,6 +7,8 @@

  #include <linux/of.h>
  #include <linux/smp.h>

+#include <asm/proc-fns.h>
+
  #define BOOT_ADDR    0x00
  #define BOOT_SIG    0x04

@@ -53,9 +55,27 @@ static void __init 

aspeed_g6_smp_prepare_cpus(unsigned int max_cpus)
      iounmap(base);
  }

+#ifdef CONFIG_HOTPLUG_CPU
+static void aspeed_g6_cpu_die(unsigned int cpu)
+{
+        /* Do WFI. If we wake up early, go back into WFI */
+        while (1)
+                cpu_do_idle();
+}
+
+static int aspeed_g6_cpu_kill(unsigned int cpu)
+{
+        return 1;
+}
+#endif
+
  static const struct smp_operations aspeed_smp_ops __initconst = {
      .smp_prepare_cpus    = aspeed_g6_smp_prepare_cpus,
      .smp_boot_secondary    = aspeed_g6_boot_secondary,
+#ifdef CONFIG_HOTPLUG_CPU
+    .cpu_die        = aspeed_g6_cpu_die,
+    .cpu_kill        = aspeed_g6_cpu_kill,
+#endif
  };

  CPU_METHOD_OF_DECLARE(aspeed_smp, "aspeed,ast2600-smp", 
&aspeed_smp_ops);

Adding Andrew Jeffery and Eddie James to the CC list.

Adding linux-kernel@vger.kernel.org and 
linux-arm-kernel@lists.infradead.org based feedback.

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