On Fri, Jun 19, 2015 at 09:46:06AM +0100, Hanjun Guo wrote:

[...]

+
+static int __init
+match_gic_redist(struct acpi_subtable_header *header, const unsigned long end)
+{
+	return 0;
+}
+static bool __init acpi_gic_redist_is_present(void)
+{
+	int count;
+
+	/* scan MADT table to find if we have redistributor entries */
+	count  =  acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_REDISTRIBUTOR,
+					match_gic_redist, 0);
+
+	/* has at least one GIC redistributor entry */
+	if (count > 0)
+		return true;
+	else
+		return false;
+}

return count > 0;

What about systems where the redistributor data is in the GICC subtable ? Do
you treat them as GIC V2 :) ?

On a side note, having to define an empty function like match_gic_redist is
horrible.

I wonder whether it is not better to refactor map_madt_entry(), create
a MADT subtable iterator out of it and make that code generic, instead
of being forced to add these useless MADT handlers just to count
entries, it is not the first I noticed.

+static int __init acpi_gic_version_init(void)
+{
+	int count;
+	void __iomem *dist_base;
+	u32 reg;
+
+	count = acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR,
+					acpi_gic_parse_distributor, 0);
+
+	if (count <= 0) {
+		pr_err("No valid GIC distributor entry exists\n");
+		return -ENODEV;
+	}
+
+	if (gic_version >= ACPI_MADT_GIC_VERSION_RESERVED) {
+		pr_err("Invalid GIC version %d in MADT\n", gic_version);
+		return -EINVAL;
+	}
+
+	/*
+	 * when the GIC version is 0, we fallback to hardware discovery.
+	 * this is also needed to keep compatiable with ACPI 5.1,
+	 * which has no gic_version field in distributor structure and
+	 * reserved as 0.
+	 *
+	 * For hardware discovery, the offset for GICv1/2 and GICv3/4 to
+	 * get the GIC version is different (0xFE8 for GICv1/2 and 0xFFE8
+	 * for GICv3/4), so we need to handle it separately.

+	 */
+	if (gic_version	== ACPI_MADT_GIC_VERSION_NONE) {
+		/* it's GICv3/v4 if redistributor is present */
+		if (acpi_gic_redist_is_present()) {

See above, IIUC you might have systems with GIC v3 where this call
would fail, and we do not want to fall back to GIC v2.

Lorenzo

+			dist_base = ioremap(dist_phy_base,
+					    ACPI_GICV3_DIST_MEM_SIZE);
+			if (!dist_base)
+				return -ENOMEM;
+
+			reg = readl_relaxed(dist_base + GICD_PIDR2) &
+					    GIC_PIDR2_ARCH_MASK;
+			if (reg == GIC_PIDR2_ARCH_GICv3)
+				gic_version = ACPI_MADT_GIC_VERSION_V3;
+			else
+				gic_version = ACPI_MADT_GIC_VERSION_V4;
+
+			iounmap(dist_base);
+		} else {
+			gic_version = ACPI_MADT_GIC_VERSION_V2;
+		}