Re: [RFC part2 PATCH 9/9] ACPI / GIC: Initialize GIC using the information in MADT

Marc Zyngier
2013-12-03T17:26:34Z

Hi Hanjun,

On 03/12/13 16:39, Hanjun Guo wrote:
> In MADT table, there are GIC cpu interface base address and
> GIC distributor base address, use them to convert GIC to ACPI.
>
> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
> ---
> arch/arm64/kernel/irq.c | 5 ++++
> drivers/acpi/plat/arm-core.c | 66 ++++++++++++++++++++++++++++++++++++------
> include/linux/acpi.h | 6 ++++
> 3 files changed, 68 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
> index 473e5db..a9e68bf 100644
> --- a/arch/arm64/kernel/irq.c
> +++ b/arch/arm64/kernel/irq.c
> @@ -25,6 +25,7 @@
> #include <linux/irq.h>
> #include <linux/smp.h>
> #include <linux/init.h>
> +#include <linux/acpi.h>
> #include <linux/irqchip.h>
> #include <linux/seq_file.h>
> #include <linux/ratelimit.h>
> @@ -78,6 +79,10 @@ void __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
> void __init init_IRQ(void)
> {
> irqchip_init();
> +
> + if (!handle_arch_irq)
> + acpi_gic_init();
> +

Why is the GIC hardcoded? How are you going to support other interrupt
controllers?

> if (!handle_arch_irq)
> panic("No interrupt controller found.");
> }
> diff --git a/drivers/acpi/plat/arm-core.c b/drivers/acpi/plat/arm-core.c
> index 17c99e1..509b847 100644
> --- a/drivers/acpi/plat/arm-core.c
> +++ b/drivers/acpi/plat/arm-core.c
> @@ -29,6 +29,7 @@
> #include <linux/module.h>
> #include <linux/irq.h>
> #include <linux/irqdomain.h>
> +#include <linux/irqchip/arm-gic.h>
> #include <linux/slab.h>
> #include <linux/bootmem.h>
> #include <linux/ioport.h>
> @@ -211,11 +212,21 @@ acpi_parse_gic(struct acpi_subtable_header *header, const unsigned long end)
> return 0;
> }
>
> +#ifdef CONFIG_ARM_GIC
> +/*
> + * Hard code here, we can not get memory size from MADT (but FDT does),
> + * this size is described in ARMv8 foudation model's User Guide
> + */
> +#define GIC_DISTRIBUTOR_MEMORY_SIZE (SZ_8K)
> +#define GIC_CPU_INTERFACE_MEMORY_SIZE (SZ_4K)

Aside from the incorrect sizes, how do you plan to address the other
regions that the GICv2 specification describes?

> static int __init
> acpi_parse_gic_distributor(struct acpi_subtable_header *header,
> const unsigned long end)
> {
> struct acpi_madt_generic_distributor *distributor = NULL;
> + void __iomem *dist_base = NULL;
> + void __iomem *cpu_base = NULL;
>
> distributor = (struct acpi_madt_generic_distributor *)header;
>
> @@ -224,8 +235,43 @@ acpi_parse_gic_distributor(struct acpi_subtable_header *header,
>
> acpi_table_print_madt_entry(header);
>
> + /* GIC is initialised after page_init(), no need for early_ioremap */
> + dist_base = ioremap(distributor->base_address,
> + GIC_CPU_INTERFACE_MEMORY_SIZE);
> + if (!dist_base) {
> + pr_warn(PREFIX "unable to map gic dist registers\n");
> + return -ENOMEM;
> + }
> +
> + /*
> + * acpi_lapic_addr is stored in acpi_parse_madt(),
> + * so we can use it here for GIC init
> + */
> + if (acpi_lapic_addr) {
> + iounmap(dist_base);
> + pr_warn(PREFIX "Invalid GIC cpu interface base address\n");
> + return -EINVAL;
> + }
> +
> + cpu_base = ioremap(acpi_lapic_addr, GIC_CPU_INTERFACE_MEMORY_SIZE);
> + if (!cpu_base) {
> + iounmap(dist_base);
> + pr_warn(PREFIX "unable to map gic cpu registers\n");
> + return -ENOMEM;
> + }
> +
> + gic_init(distributor->gic_id, -1, dist_base, cpu_base);
> +
> return 0;
> }
> +#else
> +static int __init
> +acpi_parse_gic_distributor(struct acpi_subtable_header *header,
> + const unsigned long end)
> +{
> + return -ENODEV;
> +}
> +#endif /* CONFIG_ARM_GIC */
>
> /*
> * Parse GIC cpu interface related entries in MADT
> @@ -234,7 +280,7 @@ acpi_parse_gic_distributor(struct acpi_subtable_header *header,
> static int __init acpi_parse_madt_gic_entries(void)
> {
> int count;
> -
> +
> /*
> * do a partial walk of MADT to determine how many CPUs
> * we have including disabled CPUs
> @@ -468,19 +514,21 @@ static void __init acpi_process_madt(void)
> * Parse MADT GIC cpu interface entries
> */
> error = acpi_parse_madt_gic_entries();
> - if (!error) {
> - /*
> - * Parse MADT GIC distributor entries
> - */
> - acpi_parse_madt_gic_distributor_entries();
> - }
> + if (!error)
> + pr_info("Using ACPI for processor (GIC) configuration information\n");
> }
>
> - pr_info("Using ACPI for processor (GIC) configuration information\n");
> -
> return;
> }
>
> +int __init acpi_gic_init(void)
> +{
> + /*
> + * Parse MADT GIC distributor entries
> + */
> + return acpi_parse_madt_gic_distributor_entries();
> +}
> +

Why can't you do the GIC init in the GIC code? We've tried hard to make
interrupt controllers discoverable and self contained. What are you
going to do when ACPI adds GICv3 to the mix? I don't really think this
model (shoving everything into the core ACPI code) is sustainable in the
long run...

Cheers,

M.
--
Jazz is not dead. It just smells funny...