[PATCH 08/11] x86/tsc: Remove CPUID "frequency" leaf magic numbers.

Dave Hansen
2024-11-20T19:53:38Z

From: Dave Hansen <dave.hansen@linux.intel.com>

All the code that reads the CPUID frequency information leaf hard-codes
a magic number. Give it a symbolic name and use it.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
---

b/arch/x86/include/asm/cpuid.h | 1 +
b/arch/x86/kernel/tsc.c | 12 ++++++------
2 files changed, 7 insertions(+), 6 deletions(-)

diff -puN arch/x86/include/asm/cpuid.h~tsc-leaf-checks-3 arch/x86/include/asm/cpuid.h
--- a/arch/x86/include/asm/cpuid.h~tsc-leaf-checks-3 2024-11-20 11:44:19.301730364 -0800
+++ b/arch/x86/include/asm/cpuid.h 2024-11-20 11:44:19.305730518 -0800
@@ -22,6 +22,7 @@ enum cpuid_regs_idx {
#define CPUID_MWAIT_LEAF 0x5
#define CPUID_DCA_LEAF 0x9
#define CPUID_TSC_LEAF 0x15
+#define CPUID_FREQ_LEAF 0x16

#ifdef CONFIG_X86_32
extern int have_cpuid_p(void);
diff -puN arch/x86/kernel/tsc.c~tsc-leaf-checks-3 arch/x86/kernel/tsc.c
--- a/arch/x86/kernel/tsc.c~tsc-leaf-checks-3 2024-11-20 11:44:19.305730518 -0800
+++ b/arch/x86/kernel/tsc.c 2024-11-20 11:44:19.305730518 -0800
@@ -680,8 +680,8 @@ unsigned long native_calibrate_tsc(void)

/*
* Denverton SoCs don't report crystal clock, and also don't support
- * CPUID.0x16 for the calculation below, so hardcode the 25MHz crystal
- * clock.
+ * CPUID_FREQ_LEAF for the calculation below, so hardcode the 25MHz
+ * crystal clock.
*/
if (crystal_khz == 0 &&
boot_cpu_data.x86_vfm == INTEL_ATOM_GOLDMONT_D)
@@ -700,10 +700,10 @@ unsigned long native_calibrate_tsc(void)
* clock, but we can easily calculate it to a high degree of accuracy
* by considering the crystal ratio and the CPU speed.
*/
- if (crystal_khz == 0 && boot_cpu_data.cpuid_level >= 0x16) {
+ if (crystal_khz == 0 && boot_cpu_data.cpuid_level >= CPUID_FREQ_LEAF) {
unsigned int eax_base_mhz, ebx, ecx, edx;

- cpuid(0x16, &eax_base_mhz, &ebx, &ecx, &edx);
+ cpuid(CPUID_FREQ_LEAF, &eax_base_mhz, &ebx, &ecx, &edx);
crystal_khz = eax_base_mhz * 1000 *
eax_denominator / ebx_numerator;
}
@@ -738,12 +738,12 @@ static unsigned long cpu_khz_from_cpuid(
if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
return 0;

- if (boot_cpu_data.cpuid_level < 0x16)
+ if (boot_cpu_data.cpuid_level < CPUID_FREQ_LEAF)
return 0;

eax_base_mhz = ebx_max_mhz = ecx_bus_mhz = edx = 0;

- cpuid(0x16, &eax_base_mhz, &ebx_max_mhz, &ecx_bus_mhz, &edx);
+ cpuid(CPUID_FREQ_LEAF, &eax_base_mhz, &ebx_max_mhz, &ecx_bus_mhz, &edx);

return eax_base_mhz * 1000;
}
_