diff options
Diffstat (limited to 'arch/arm64/kernel/acpi.c')
| -rw-r--r-- | arch/arm64/kernel/acpi.c | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c index cada0b816c8a..f3851724fe35 100644 --- a/arch/arm64/kernel/acpi.c +++ b/arch/arm64/kernel/acpi.c @@ -239,6 +239,18 @@ done: } } +static pgprot_t __acpi_get_writethrough_mem_attribute(void) +{ + /* + * Although UEFI specifies the use of Normal Write-through for + * EFI_MEMORY_WT, it is seldom used in practice and not implemented + * by most (all?) CPUs. Rather than allocate a MAIR just for this + * purpose, emit a warning and use Normal Non-cacheable instead. + */ + pr_warn_once("No MAIR allocation for EFI_MEMORY_WT; treating as Normal Non-cacheable\n"); + return __pgprot(PROT_NORMAL_NC); +} + pgprot_t __acpi_get_mem_attribute(phys_addr_t addr) { /* @@ -246,7 +258,7 @@ pgprot_t __acpi_get_mem_attribute(phys_addr_t addr) * types" of UEFI 2.5 section 2.3.6.1, each EFI memory type is * mapped to a corresponding MAIR attribute encoding. * The EFI memory attribute advises all possible capabilities - * of a memory region. We use the most efficient capability. + * of a memory region. */ u64 attr; @@ -254,10 +266,10 @@ pgprot_t __acpi_get_mem_attribute(phys_addr_t addr) attr = efi_mem_attributes(addr); if (attr & EFI_MEMORY_WB) return PAGE_KERNEL; - if (attr & EFI_MEMORY_WT) - return __pgprot(PROT_NORMAL_WT); if (attr & EFI_MEMORY_WC) return __pgprot(PROT_NORMAL_NC); + if (attr & EFI_MEMORY_WT) + return __acpi_get_writethrough_mem_attribute(); return __pgprot(PROT_DEVICE_nGnRnE); } @@ -340,10 +352,10 @@ void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size) default: if (region->attribute & EFI_MEMORY_WB) prot = PAGE_KERNEL; - else if (region->attribute & EFI_MEMORY_WT) - prot = __pgprot(PROT_NORMAL_WT); else if (region->attribute & EFI_MEMORY_WC) prot = __pgprot(PROT_NORMAL_NC); + else if (region->attribute & EFI_MEMORY_WT) + prot = __acpi_get_writethrough_mem_attribute(); } } return __ioremap(phys, size, prot); |