linux-kernel - [PATCH RFC 1/1] arm64: Use PSCI calls for CPU stop when hotplug is supported

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Date:   Fri, 18 Jan 2019 11:16:20 +0530
From:   Pramod Kumar <pramod.kumar@...adcom.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>
Cc:     Suzuki K Poulose <Suzuki.Poulose@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Dave Martin <dave.martin@....com>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Steve Capper <steve.capper@....com>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Pramod Kumar <pramod.kumar@...adcom.com>
Subject: [PATCH RFC 1/1] arm64: Use PSCI calls for CPU stop when hotplug is supported

If CPU hotplug is supported, ipi_cpu_stop should use PSCI cpudie
call to stop the CPU. This call ensures L1/L2 cache flush,
CPUs cache-cohenrecy setting w.r.to interconnect.

Apart from this, this gives control to f/w to reduce power consumption
by take appropriate decesion on power rails for plugging-out core.

Signed-off-by: Pramod Kumar <pramod.kumar@...adcom.com>
Reviewed-by: Ray Jui <ray.jui@...adcom.com>
Reviewed-by: Scott Branden <scott.branden@...adcom.com>
---
 arch/arm64/kernel/smp.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 1598d6f..360e52b 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -822,8 +822,13 @@ static void ipi_cpu_stop(unsigned int cpu)
 	local_daif_mask();
 	sdei_mask_local_cpu();
 
+#ifdef CONFIG_HOTPLUG_CPU
+	if (cpu_ops[cpu]->cpu_die)
+		cpu_ops[cpu]->cpu_die(cpu);
+#else
 	while (1)
 		cpu_relax();
+#endif
 }
 
 #ifdef CONFIG_KEXEC_CORE
-- 
1.9.1