[PATCH v6 1/1] 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 <lpieralisi@kernel.org>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Cc: Thomas Gleixner <redacted>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
---
  drivers/acpi/processor_core.c    | 15 +++++++++++++++
  drivers/irqchip/irq-gic-v3-its.c |  4 ++++
  drivers/irqchip/irq-gic-v3.c     |  9 +++++++++
  include/linux/acpi.h             |  3 +++
  4 files changed, 31 insertions(+)

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 };

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 40ebf1726393..af5297ef2293 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c

@@ -5600,6 +5600,10 @@ static int __init gic_acpi_parse_madt_its(union acpi_subtable_headers *header,
  		goto node_err;
  	}
  
+	if (acpi_get_madt_revision() >= 7 &&
+	    (its_entry->flags & ACPI_MADT_ITS_NON_COHERENT))
+		its->flags |= ITS_FLAGS_FORCE_NON_SHAREABLE;
+
  	err = its_probe_one(its);
  	if (!err)
  		return 0;

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 6fb276504bcc..e4bc5f04226e 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c

@@ -2349,6 +2349,11 @@ gic_acpi_parse_madt_redist(union acpi_subtable_headers *header,
  		pr_err("Couldn't map GICR region @%llx\n", redist->base_address);
  		return -ENOMEM;
  	}
+
+	if (acpi_get_madt_revision() >= 7 &&
+	    (redist->flags & ACPI_MADT_GICR_NON_COHERENT))
+		gic_data.rdists.flags |= RDIST_FLAGS_FORCE_NON_SHAREABLE;
+
  	gic_request_region(redist->base_address, redist->length, "GICR");
  
  	gic_acpi_register_redist(redist->base_address, redist_base);

@@ -2373,6 +2378,10 @@ gic_acpi_parse_madt_gicc(union acpi_subtable_headers *header,
  		return -ENOMEM;
  	gic_request_region(gicc->gicr_base_address, size, "GICR");
  
+	if (acpi_get_madt_revision() >= 7 &&
+	    (gicc->flags & ACPI_MADT_GICC_NON_COHERENT))
+		gic_data.rdists.flags |= RDIST_FLAGS_FORCE_NON_SHAREABLE;
+
  	gic_acpi_register_redist(gicc->gicr_base_address, redist_base);
  	return 0;
  }

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 28c3fb2bef0d..000d339e1596 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h

@@ -279,6 +279,9 @@ static inline bool invalid_phys_cpuid(phys_cpuid_t phys_id)
  	return phys_id == PHYS_CPUID_INVALID;
  }
  
+
+int __init acpi_get_madt_revision(void);
+
  /* Validate the processor object's proc_id */
  bool acpi_duplicate_processor_id(int proc_id);
  /* Processor _CTS control */