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

[Marc Zyngier]

On 04/12/13 15:32, Hanjun Guo wrote:
> On 2013å12æ04æ 01:26, Marc Zyngier wrote:
>> 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@xxxxxxxxxx>
>>> ---
>>>   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?
> 
> Very good question, thanks. I considered GIC only in my patch set.
> I have no idea how to handle the GIC hardcoded problem here for
> now, but I will figure it out later.
> 
> If any suggestion, I will appreciate a lot.
> 
>> How are you going to support other interrupt
>> controllers?
> 
> ACPI 5.0 supports GICv2 only for now, if we want to
> support other interrupt controller, we should introduce
> some OEM table and parsing it, and it will not covered
> by this patch set.
> 
>>>   	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?
> 
> Did these regions have the same base address? I mean the same
> as GIC distributor base address and GIC cpu interface base address.
> 
> if yes, since the base address is stored in gic_init(), it can be for 
> furture
> use. if I misunderstood your question, please let me know.

Look at the VGIC implementation for KVM in virt/kvm/arm. It does its own
probing of the additional regions used for virtualization.

The GIC and VGIC code are completely separate, and you'll need to find
an acceptable solution for that too.

>>>   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.
> 
> thanks for your suggestion, Rob also had the same suggestion,
> will try to update it in next version.
> 
>> 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...
> 
> Since GICv3 related ACPI proposal is not public and not goes into ACPI
> spec, my suggestion is that we implement GICv2 only for now and post
> another patches for GICv3 when the new ACPI spec is available.

Certainly. But I think you should aim for a scalable solution right
away, instead of starting with something that we already know won't work
for stuff that is already around the corner (which is what I infer from
your "non public" statement).

Cheers,

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

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