linux-kernel - [PATCH] cpufreq: Simplify MSR read on the boot CPU

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Message-Id: <20241106182313.165297-1-chang.seok.bae@intel.com>
Date: Wed,  6 Nov 2024 10:23:13 -0800
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: rafael@...nel.org,
	viresh.kumar@...aro.org,
	dave.hansen@...el.com,
	bp@...en8.de,
	chang.seok.bae@...el.com
Subject: [PATCH] cpufreq: Simplify MSR read on the boot CPU

Replace the 32-bit MSR access function with a 64-bit variant to simplify
the call site, eliminating unnecessary 32-bit value manipulations.

Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
Cc: Rafael J. Wysocki <rafael@...nel.org>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Borislav Petkov <bp@...en8.de>
---
I've received feedback to use rdmsrl_on_cpu() instead of rdmsr_on_cpu()
for similar code in my feature-enabling series [1]. While auditing the
tree, I found this case as well, so here's another cleanup.

[1] https://lore.kernel.org/lkml/e9afefb7-3c4e-48ee-aab1-2f338c4e989d@intel.com/
---
 drivers/cpufreq/acpi-cpufreq.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 0f04feb6cafa..b942cd11e179 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -73,20 +73,17 @@ static unsigned int acpi_pstate_strict;
 
 static bool boost_state(unsigned int cpu)
 {
-	u32 lo, hi;
 	u64 msr;
 
 	switch (boot_cpu_data.x86_vendor) {
 	case X86_VENDOR_INTEL:
 	case X86_VENDOR_CENTAUR:
 	case X86_VENDOR_ZHAOXIN:
-		rdmsr_on_cpu(cpu, MSR_IA32_MISC_ENABLE, &lo, &hi);
-		msr = lo | ((u64)hi << 32);
+		rdmsrl_on_cpu(cpu, MSR_IA32_MISC_ENABLE, &msr);
 		return !(msr & MSR_IA32_MISC_ENABLE_TURBO_DISABLE);
 	case X86_VENDOR_HYGON:
 	case X86_VENDOR_AMD:
-		rdmsr_on_cpu(cpu, MSR_K7_HWCR, &lo, &hi);
-		msr = lo | ((u64)hi << 32);
+		rdmsrl_on_cpu(cpu, MSR_K7_HWCR, &msr);
 		return !(msr & MSR_K7_HWCR_CPB_DIS);
 	}
 	return false;
-- 
2.34.1