irqchip/gic-v3: Enable non-coherent redistributors/ITSes ACPI probing

The GIC architecture specification defines a set of registers for
redistributors and ITSes that control the sharebility and cacheability
attributes of redistributors/ITSes initiator ports on the interconnect
(GICR_[V]PROPBASER, GICR_[V]PENDBASER, GITS_BASER<n>).

Architecturally the GIC provides a means to drive shareability and
cacheability attributes signals but it is not mandatory for designs to
wire up the corresponding interconnect signals that control the
cacheability/shareability of transactions.

Redistributors and ITSes interconnect ports can be connected to
non-coherent interconnects that are not able to manage the
shareability/cacheability attributes; this implicitly makes the
redistributors and ITSes non-coherent observers.

To enable non-coherent GIC designs on ACPI based systems, parse the MADT
GICC/GICR/ITS subtables non-coherent flags to determine whether the
respective components are non-coherent observers and force the
shareability attributes to be programmed into the redistributors and
ITSes registers.

An ACPI global function (acpi_get_madt_revision()) is added to retrieve
the MADT revision, in that it is essential to check the MADT revision
before checking for flags that were added with MADT revision 7 so that
if the kernel is booted with an ACPI MADT table with revision < 7 it
skips parsing the newly added flags (that should be zeroed reserved
values for MADT versions < 7 but they could turn out to be buggy and
should be ignored).

Signed-off-by: Lorenzo Pieralisi <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Robin Murphy <[email protected]>
Acked-by: Marc Zyngier <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
index b203cfe28550..915713c0e9b7 100644
--- a/drivers/acpi/processor_core.c
+++ b/drivers/acpi/processor_core.c
@@ -215,6 +215,21 @@ phys_cpuid_t __init acpi_map_madt_entry(u32 acpi_id)
 	return rv;
 }
 
+int __init acpi_get_madt_revision(void)
+{
+	struct acpi_table_header *madt = NULL;
+	int revision;
+
+	if (ACPI_FAILURE(acpi_get_table(ACPI_SIG_MADT, 0, &madt)))
+		return -EINVAL;
+
+	revision = madt->revision;
+
+	acpi_put_table(madt);
+
+	return revision;
+}
+
 static phys_cpuid_t map_mat_entry(acpi_handle handle, int type, u32 acpi_id)
 {
 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };