diff options
Diffstat (limited to 'arch/x86/kernel/hpet.c')
| -rw-r--r-- | arch/x86/kernel/hpet.c | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index c6f791bc481e..9834d221e390 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -9,6 +9,7 @@ #include <asm/hpet.h> #include <asm/time.h> +#include <asm/mwait.h> #undef pr_fmt #define pr_fmt(fmt) "hpet: " fmt @@ -806,6 +807,83 @@ static bool __init hpet_counting(void) return false; } +static bool __init mwait_pc10_supported(void) +{ + unsigned int eax, ebx, ecx, mwait_substates; + + if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) + return false; + + if (!cpu_feature_enabled(X86_FEATURE_MWAIT)) + return false; + + if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) + return false; + + cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates); + + return (ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) && + (ecx & CPUID5_ECX_INTERRUPT_BREAK) && + (mwait_substates & (0xF << 28)); +} + +/* + * Check whether the system supports PC10. If so force disable HPET as that + * stops counting in PC10. This check is overbroad as it does not take any + * of the following into account: + * + * - ACPI tables + * - Enablement of intel_idle + * - Command line arguments which limit intel_idle C-state support + * + * That's perfectly fine. HPET is a piece of hardware designed by committee + * and the only reasons why it is still in use on modern systems is the + * fact that it is impossible to reliably query TSC and CPU frequency via + * CPUID or firmware. + * + * If HPET is functional it is useful for calibrating TSC, but this can be + * done via PMTIMER as well which seems to be the last remaining timer on + * X86/INTEL platforms that has not been completely wreckaged by feature + * creep. + * + * In theory HPET support should be removed altogether, but there are older + * systems out there which depend on it because TSC and APIC timer are + * dysfunctional in deeper C-states. + * + * It's only 20 years now that hardware people have been asked to provide + * reliable and discoverable facilities which can be used for timekeeping + * and per CPU timer interrupts. + * + * The probability that this problem is going to be solved in the + * forseeable future is close to zero, so the kernel has to be cluttered + * with heuristics to keep up with the ever growing amount of hardware and + * firmware trainwrecks. Hopefully some day hardware people will understand + * that the approach of "This can be fixed in software" is not sustainable. + * Hope dies last... + */ +static bool __init hpet_is_pc10_damaged(void) +{ + unsigned long long pcfg; + + /* Check whether PC10 substates are supported */ + if (!mwait_pc10_supported()) + return false; + + /* Check whether PC10 is enabled in PKG C-state limit */ + rdmsrl(MSR_PKG_CST_CONFIG_CONTROL, pcfg); + if ((pcfg & 0xF) < 8) + return false; + + if (hpet_force_user) { + pr_warn("HPET force enabled via command line, but dysfunctional in PC10.\n"); + return false; + } + + pr_info("HPET dysfunctional in PC10. Force disabled.\n"); + boot_hpet_disable = true; + return true; +} + /** * hpet_enable - Try to setup the HPET timer. Returns 1 on success. */ @@ -819,6 +897,9 @@ int __init hpet_enable(void) if (!is_hpet_capable()) return 0; + if (hpet_is_pc10_damaged()) + return 0; + hpet_set_mapping(); if (!hpet_virt_address) return 0; |