[PATCH v3] arm64: Clarify when cpu_enable() is called

[PATCH v3] arm64: Clarify when cpu_enable() is called

[Mark Brown]

Strengthen the wording in the documentation for cpu_enable() to make it
more obvious to readers not already familiar with the code when the core
will call this callback and that this is intentional.

Signed-off-by: Mark Brown <broonie@kernel.org>
---

v3: Whitespace
v2: Much more verbose wording from Suzuki.

 arch/arm64/include/asm/cpufeature.h | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index cf65a47ee6b4..eaeb030d0b95 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -289,9 +289,16 @@ struct arm64_cpu_capabilities {
 	u16 type;
 	bool (*matches)(const struct arm64_cpu_capabilities *caps, int scope);
 	/*
-	 * Take the appropriate actions to enable this capability for this CPU.
-	 * For each successfully booted CPU, this method is called for each
-	 * globally detected capability.
+	 * Take the appropriate actions to configure this capability
+	 * for this CPU. If the capability is detected by the kernel
+	 * this will be called on all the CPUs in the system,
+	 * including the hotplugged CPUs, regardless of if the
+	 * capability was *available* on that specific CPU. This is
+	 * useful for some capabilities (e.g, working around CPU
+	 * errata), where all the CPUs must take some action (e.g,
+	 * changing system control/configuration). Thus, if an action
+	 * is required only if the CPU has the capability, then the
+	 * routine must check it before taking any action.
 	 */
 	void (*cpu_enable)(const struct arm64_cpu_capabilities *cap);
 	union {
-- 
2.20.1


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Re: [PATCH v3] arm64: Clarify when cpu_enable() is called

[Mark Brown]

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On Thu, Aug 08, 2019 at 03:05:54PM +0100, Mark Brown wrote:
> Strengthen the wording in the documentation for cpu_enable() to make it
> more obvious to readers not already familiar with the code when the core
> will call this callback and that this is intentional.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>

Missed this at the bottom of Suzuki's mail sorry:

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

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