[PATCH v2] ACPI: RIMT: Enable PCI ACS for root complexes mapped to an IOMMU

[fangyu . yu]

From: Fangyu Yu <fangyu.yu@xxxxxxxxxxxxxxxxx>

Mirror the ACPI IORT solution used on arm64 (see iort_enable_acs())
by scanning the RIMT table for PCIe root complex nodes during
riscv_acpi_rimt_init(), which runs before ACPI PCI enumeration. If a
root complex node's ID mapping points at an IOMMU node, call
pci_request_acs() immediately, so pci_acs_enable is already set by
the time any PCI device is scanned and pci_enable_acs() runs.

Only one call to pci_request_acs() is needed regardless of how many
root complexes are found, so track that with a static acs_enabled
flag, same as iort_enable_acs() does.

Signed-off-by: Fangyu Yu <fangyu.yu@xxxxxxxxxxxxxxxxx>
Reviewed-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>

---
Changes in v2 (Suggested by Sunil):
    - Check the RIMT node type in riscv_acpi_rimt_init() and invoke
      rimt_enable_acs() only for PCIe root-complex nodes.
---
 drivers/acpi/riscv/rimt.c | 58 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/drivers/acpi/riscv/rimt.c b/drivers/acpi/riscv/rimt.c
index e4538fa6c2c8..edbd04a9e03b 100644
--- a/drivers/acpi/riscv/rimt.c
+++ b/drivers/acpi/riscv/rimt.c
@@ -179,6 +179,42 @@ static struct acpi_rimt_node *rimt_scan_node(enum acpi_rimt_node_type type,
 	return NULL;
 }
 
+#ifdef CONFIG_PCI
+static void __init rimt_enable_acs(struct acpi_rimt_node *rimt_node)
+{
+	static bool acs_enabled __initdata;
+	struct acpi_rimt_pcie_rc *pci_rc;
+	struct acpi_rimt_id_mapping *map;
+	struct acpi_rimt_node *parent;
+	int i;
+
+	if (acs_enabled)
+		return;
+
+	pci_rc = (struct acpi_rimt_pcie_rc *)rimt_node->node_data;
+	if (!pci_rc->id_mapping_offset || !pci_rc->num_id_mappings)
+		return;
+
+	map = ACPI_ADD_PTR(struct acpi_rimt_id_mapping, rimt_node,
+			   pci_rc->id_mapping_offset);
+
+	for (i = 0; i < pci_rc->num_id_mappings; i++, map++) {
+		if (!map->dest_offset)
+			continue;
+
+		parent = ACPI_ADD_PTR(struct acpi_rimt_node, rimt_table,
+				      map->dest_offset);
+		if (parent->type == ACPI_RIMT_NODE_TYPE_IOMMU) {
+			pci_request_acs();
+			acs_enabled = true;
+			return;
+		}
+	}
+}
+#else
+static inline void rimt_enable_acs(struct acpi_rimt_node *rimt_node) { }
+#endif
+
 /*
  * RISC-V supports IOMMU as a PCI device or a platform device.
  * When it is a platform device, there should be a namespace device as
@@ -509,7 +545,10 @@ int rimt_iommu_configure_id(struct device *dev, const u32 *id_in)
 
 void __init riscv_acpi_rimt_init(void)
 {
+	struct acpi_rimt_node *rimt_node, *rimt_end;
+	struct acpi_table_rimt *rimt;
 	acpi_status status;
+	int i;
 
 	/* rimt_table will be used at runtime after the rimt init,
 	 * so we don't need to call acpi_put_table() to release
@@ -525,4 +564,23 @@ void __init riscv_acpi_rimt_init(void)
 
 		return;
 	}
+
+	rimt = (struct acpi_table_rimt *)rimt_table;
+	rimt_node = ACPI_ADD_PTR(struct acpi_rimt_node, rimt,
+				 rimt->node_offset);
+	rimt_end = ACPI_ADD_PTR(struct acpi_rimt_node, rimt_table,
+				rimt_table->length);
+
+	for (i = 0; i < rimt->num_nodes; i++) {
+		if (rimt_node >= rimt_end) {
+			pr_err("RIMT node pointer overflows, bad table\n");
+			return;
+		}
+
+		if (rimt_node->type == ACPI_RIMT_NODE_TYPE_PCIE_ROOT_COMPLEX)
+			rimt_enable_acs(rimt_node);
+
+		rimt_node = ACPI_ADD_PTR(struct acpi_rimt_node, rimt_node,
+					 rimt_node->length);
+	}
 }
-- 
2.50.1