Hi Marc,

On 16.01.2015 12:15, Marc Zyngier wrote:

On 14/01/15 15:05, Hanjun Guo wrote:

quoted

From: Tomasz Nowicki <redacted>

ACPI kernel uses MADT table for proper GIC initialization. It needs to
parse GIC related subtables, collect CPU interface and distributor
addresses and call driver initialization function (which is hardware
abstraction agnostic). In a similar way, FDT initialize GICv1/2.

NOTE: This commit allow to initialize GICv1/2 basic functionality.
GICv2 vitalization extension, GICv3/4 and ITS are considered as next
steps.

And so is GICv2m, apparently (see below).

quoted

Tested-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Tested-by: Yijing Wang <redacted>
Signed-off-by: Tomasz Nowicki <redacted>
Signed-off-by: Hanjun Guo <redacted>
---
  arch/arm64/kernel/acpi.c             |  26 +++++++++
  drivers/irqchip/irq-gic.c            | 108 +++++++++++++++++++++++++++++++++++
  drivers/irqchip/irqchip.c            |   3 +
  include/linux/irqchip/arm-gic-acpi.h |  31 ++++++++++
  4 files changed, 168 insertions(+)
  create mode 100644 include/linux/irqchip/arm-gic-acpi.h

diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index c3e24c4..ea3c9fc 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c

@@ -23,6 +23,7 @@
  #include <linux/irqdomain.h>
  #include <linux/bootmem.h>
  #include <linux/smp.h>
+#include <linux/irqchip/arm-gic-acpi.h>

  #include <asm/cputype.h>
  #include <asm/cpu_ops.h>

@@ -315,6 +316,31 @@ void __init acpi_boot_table_init(void)
  		pr_err("Can't find FADT or error happened during parsing FADT\n");
  }

+void __init acpi_gic_init(void)
+{
+	struct acpi_table_header *table;
+	acpi_status status;
+	acpi_size tbl_size;
+	int err;
+
+	if (acpi_disabled)
+		return;
+
+	status = acpi_get_table_with_size(ACPI_SIG_MADT, 0, &table, &tbl_size);
+	if (ACPI_FAILURE(status)) {
+		const char *msg = acpi_format_exception(status);
+
+		pr_err("Failed to get MADT table, %s\n", msg);
+		return;
+	}
+
+	err = gic_v2_acpi_init(table);
+	if (err)
+		pr_err("Failed to initialize GIC IRQ controller");
+
+	early_acpi_os_unmap_memory((char *)table, tbl_size);
+}
+
  static int __init parse_acpi(char *arg)
  {
  	if (!arg)

diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index d617ee5..89a8120 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c

@@ -33,12 +33,14 @@
  #include <linux/of.h>
  #include <linux/of_address.h>
  #include <linux/of_irq.h>
+#include <linux/acpi.h>
  #include <linux/irqdomain.h>
  #include <linux/interrupt.h>
  #include <linux/percpu.h>
  #include <linux/slab.h>
  #include <linux/irqchip/chained_irq.h>
  #include <linux/irqchip/arm-gic.h>
+#include <linux/irqchip/arm-gic-acpi.h>

  #include <asm/cputype.h>
  #include <asm/irq.h>

@@ -1083,3 +1085,109 @@ IRQCHIP_DECLARE(msm_8660_qgic, "qcom,msm-8660-qgic", gic_of_init);
  IRQCHIP_DECLARE(msm_qgic2, "qcom,msm-qgic2", gic_of_init);

  #endif
+
+#ifdef CONFIG_ACPI
+static phys_addr_t dist_phy_base, cpu_phy_base;
+static int cpu_base_assigned;
+
+static int __init
+gic_acpi_parse_madt_cpu(struct acpi_subtable_header *header,
+			const unsigned long end)
+{
+	struct acpi_madt_generic_interrupt *processor;
+	phys_addr_t gic_cpu_base;
+
+	processor = (struct acpi_madt_generic_interrupt *)header;
+
+	if (BAD_MADT_ENTRY(processor, end))
+		return -EINVAL;
+
+	/*
+	 * There is no support for non-banked GICv1/2 register in ACPI spec.
+	 * All CPU interface addresses have to be the same.
+	 */
+	gic_cpu_base = processor->base_address;
+	if (cpu_base_assigned && gic_cpu_base != cpu_phy_base)
+		return -EFAULT;

EFAULT? That feels weird. This error code should be returned if an
access would generate (or has actually generated) a fault, but this is
not the case here. Same for the other cases below.

Right, will fix that and other cases too.

quoted

+
+	cpu_phy_base = gic_cpu_base;
+	cpu_base_assigned = 1;
+	return 0;
+}
+
+static int __init
+gic_acpi_parse_madt_distributor(struct acpi_subtable_header *header,
+				const unsigned long end)
+{
+	struct acpi_madt_generic_distributor *dist;
+
+	dist = (struct acpi_madt_generic_distributor *)header;
+
+	if (BAD_MADT_ENTRY(dist, end))
+		return -EINVAL;
+
+	dist_phy_base = dist->base_address;
+	return 0;
+}
+
+int __init
+gic_v2_acpi_init(struct acpi_table_header *table)
+{
+	void __iomem *cpu_base, *dist_base;
+	int count;
+
+	/* Collect CPU base addresses */
+	count = acpi_parse_entries(ACPI_SIG_MADT,
+				   sizeof(struct acpi_table_madt),
+				   gic_acpi_parse_madt_cpu, table,
+				   ACPI_MADT_TYPE_GENERIC_INTERRUPT, 0);
+	if (count < 0) {
+		pr_err("Error during GICC entries parsing\n");
+		return -EFAULT;
+	} else if (!count) {
+		pr_err("No valid GICC entries exist\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Find distributor base address. We expect one distributor entry since
+	 * ACPI 5.1 spec neither support multi-GIC instances nor GIC cascade.
+	 */
+	count = acpi_parse_entries(ACPI_SIG_MADT,
+				   sizeof(struct acpi_table_madt),
+				   gic_acpi_parse_madt_distributor, table,
+				   ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR, 0);
+	if (count <= 0) {
+		pr_err("Error during GICD entries parsing\n");
+		return -EFAULT;
+	} else if (!count) {
+		pr_err("No valid GICD entries exist\n");
+		return -EINVAL;
+	} else if (count > 1) {
+		pr_err("More than one GICD entry detected\n");
+		return -EINVAL;
+	}
+
+	cpu_base = ioremap(cpu_phy_base, ACPI_GIC_CPU_IF_MEM_SIZE);
+	if (!cpu_base) {
+		pr_err("Unable to map GICC registers\n");
+		return -ENOMEM;
+	}
+
+	dist_base = ioremap(dist_phy_base, ACPI_GICV2_DIST_MEM_SIZE);
+	if (!dist_base) {
+		pr_err("Unable to map GICD registers\n");
+		iounmap(cpu_base);
+		return -ENOMEM;
+	}
+
+	/*
+	 * Initialize zero GIC instance (no multi-GIC support). Also, set GIC
+	 * as default IRQ domain to allow for GSI registration and GSI to IRQ
+	 * number translation (see acpi_register_gsi() and acpi_gsi_to_irq()).
+	 */
+	gic_init_bases(0, -1, dist_base, cpu_base, 0, NULL);

I assume you never tried to port the GICv2m driver to ACPI, right?
Because the above code actively prevents the GIC domain to be defined as
a stacked domain, making it impossible for the v2m widget to be
implemented on top of GIC. But maybe legacy interrupts are enough?

Yes, since stacked domain patches were merged to 3.19 we need to go back 
to this. Some of us have already started addressing your comment.

Regards,
Tomasz