diff options
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/acpi/boot.c | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/i8259.c | 38 |
2 files changed, 33 insertions, 8 deletions
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c index 0f762070a5e1..2252340b2133 100644 --- a/arch/x86/kernel/acpi/boot.c +++ b/arch/x86/kernel/acpi/boot.c @@ -147,6 +147,9 @@ static int __init acpi_parse_madt(struct acpi_table_header *table) pr_debug("Local APIC address 0x%08x\n", madt->address); } + if (madt->flags & ACPI_MADT_PCAT_COMPAT) + legacy_pic_pcat_compat(); + /* ACPI 6.3 and newer support the online capable bit. */ if (acpi_gbl_FADT.header.revision > 6 || (acpi_gbl_FADT.header.revision == 6 && diff --git a/arch/x86/kernel/i8259.c b/arch/x86/kernel/i8259.c index f91e5e31aa4f..2ac5f488300c 100644 --- a/arch/x86/kernel/i8259.c +++ b/arch/x86/kernel/i8259.c @@ -32,6 +32,7 @@ */ static void init_8259A(int auto_eoi); +static bool pcat_compat __ro_after_init; static int i8259A_auto_eoi; DEFINE_RAW_SPINLOCK(i8259A_lock); @@ -301,15 +302,32 @@ static void unmask_8259A(void) static int probe_8259A(void) { + unsigned char new_val, probe_val = ~(1 << PIC_CASCADE_IR); unsigned long flags; - unsigned char probe_val = ~(1 << PIC_CASCADE_IR); - unsigned char new_val; + + /* + * If MADT has the PCAT_COMPAT flag set, then do not bother probing + * for the PIC. Some BIOSes leave the PIC uninitialized and probing + * fails. + * + * Right now this causes problems as quite some code depends on + * nr_legacy_irqs() > 0 or has_legacy_pic() == true. This is silly + * when the system has an IO/APIC because then PIC is not required + * at all, except for really old machines where the timer interrupt + * must be routed through the PIC. So just pretend that the PIC is + * there and let legacy_pic->init() initialize it for nothing. + * + * Alternatively this could just try to initialize the PIC and + * repeat the probe, but for cases where there is no PIC that's + * just pointless. + */ + if (pcat_compat) + return nr_legacy_irqs(); + /* - * Check to see if we have a PIC. - * Mask all except the cascade and read - * back the value we just wrote. If we don't - * have a PIC, we will read 0xff as opposed to the - * value we wrote. + * Check to see if we have a PIC. Mask all except the cascade and + * read back the value we just wrote. If we don't have a PIC, we + * will read 0xff as opposed to the value we wrote. */ raw_spin_lock_irqsave(&i8259A_lock, flags); @@ -431,5 +449,9 @@ static int __init i8259A_init_ops(void) return 0; } - device_initcall(i8259A_init_ops); + +void __init legacy_pic_pcat_compat(void) +{ + pcat_compat = true; +} |