Apple ARM SoCs (A11 and newer) have some interrupt sources hard-wired to the FIQ line. Introduce a cpufeature that can be used to enable FIQ unmasking and handling via alternatives.
This is currently enabled for all Apple CPUs. If/when support is implemented for older (pre-A11) iPhone/iPad SoCs which do not need FIQs, or if newer SoCs are released without the FIQ requirement, we can revisit the condition. Signed-off-by: Hector Martin <[email protected]> --- arch/arm64/Kconfig | 10 +++++++++ arch/arm64/include/asm/cpucaps.h | 3 ++- arch/arm64/include/asm/cpufeature.h | 6 ++++++ arch/arm64/include/asm/cputype.h | 1 + arch/arm64/kernel/cpufeature.c | 32 +++++++++++++++++++++++++++++ 5 files changed, 51 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index f39568b28ec1..11cfdc07404f 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1756,6 +1756,16 @@ config ARM64_DEBUG_PRIORITY_MASKING If unsure, say N endif +config ARM64_FIQ_SUPPORT + bool "Support for FIQ interrupts" + help + Adds support for handling FIQ interrupts as normal IRQs. + This is required on Apple platforms where some IRQ sources are + hardwired to the FIQ interrupt line. + + FIQs are only enabled at runtime on platforms that require them + via the CPU feature framework. + config RELOCATABLE bool "Build a relocatable kernel image" if EXPERT select ARCH_HAS_RELR diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h index b77d997b173b..c36d926ad801 100644 --- a/arch/arm64/include/asm/cpucaps.h +++ b/arch/arm64/include/asm/cpucaps.h @@ -66,7 +66,8 @@ #define ARM64_WORKAROUND_1508412 58 #define ARM64_HAS_LDAPR 59 #define ARM64_KVM_PROTECTED_MODE 60 +#define ARM64_NEEDS_FIQ 61 -#define ARM64_NCAPS 61 +#define ARM64_NCAPS 62 #endif /* __ASM_CPUCAPS_H */ diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 9a555809b89c..3a00cfb347c9 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -716,6 +716,12 @@ static __always_inline bool system_uses_irq_prio_masking(void) cpus_have_const_cap(ARM64_HAS_IRQ_PRIO_MASKING); } +static __always_inline bool system_uses_fiqs(void) +{ + return IS_ENABLED(CONFIG_ARM64_FIQ_SUPPORT) && + cpus_have_const_cap(ARM64_NEEDS_FIQ); +} + static inline bool system_supports_mte(void) { return IS_ENABLED(CONFIG_ARM64_MTE) && diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h index ef5b040dee44..2084a0340d16 100644 --- a/arch/arm64/include/asm/cputype.h +++ b/arch/arm64/include/asm/cputype.h @@ -59,6 +59,7 @@ #define ARM_CPU_IMP_NVIDIA 0x4E #define ARM_CPU_IMP_FUJITSU 0x46 #define ARM_CPU_IMP_HISI 0x48 +#define ARM_CPU_IMP_APPLE 0x61 #define ARM_CPU_PART_AEM_V8 0xD0F #define ARM_CPU_PART_FOUNDATION 0xD00 diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index e99eddec0a46..0863cf7cf807 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1237,6 +1237,29 @@ static bool has_cache_idc(const struct arm64_cpu_capabilities *entry, return ctr & BIT(CTR_IDC_SHIFT); } +static void cpu_sync_irq_to_fiq(struct arm64_cpu_capabilities const *cap) +{ + u64 daif = read_sysreg(daif); + + /* + * By this point in the boot process IRQs are likely masked and FIOs + * aren't, so we need to sync things to avoid spurious early FIQs. + */ + + if (daif & PSR_I_BIT) + daif |= PSR_F_BIT; + else + daif &= ~PSR_F_BIT; + + write_sysreg(daif, daif); +} + +static bool needs_fiq(const struct arm64_cpu_capabilities *entry, int __unused) +{ + /* All supported Apple cores need this */ + return read_cpuid_implementor() == ARM_CPU_IMP_APPLE; +} + static void cpu_emulate_effective_ctr(const struct arm64_cpu_capabilities *__unused) { /* @@ -2154,6 +2177,15 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .matches = has_cpuid_feature, .min_field_value = 1, }, +#ifdef CONFIG_ARM64_FIQ_SUPPORT + { + .desc = "FIQs", + .capability = ARM64_NEEDS_FIQ, + .type = ARM64_CPUCAP_BOOT_CPU_FEATURE, + .matches = needs_fiq, + .cpu_enable = cpu_sync_irq_to_fiq, + }, +#endif {}, }; -- 2.30.0
