On 2014-2-22 19:30, Marc Zyngier wrote:
On 2014-02-22 10:21, Hanjun Guo wrote:
On 2014-2-21 20:37, Sudeep Holla wrote:
Hi Hanjun,
(Adding MarcZ for his views on GIC)
On 20/02/14 03:59, Hanjun Guo wrote:
Hi Sudeep,
Thanks for your comments, please refer to the replies below. :)
On 2014年02月19日 22:33, Sudeep Holla wrote:
Hi Hanjun,
On 18/02/14 16:23, Hanjun Guo wrote:
Get apic id from MADT or _MAT method is not implemented on arm/arm64, and ACPI 5.0 introduces GIC Structure for it, so this patch introduces map_gic_id() to get apic id followed the ACPI 5.0 spec.
Signed-off-by: Hanjun Guo hanjun.guo@linaro.org
drivers/acpi/processor_core.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+)
diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c index 4dcf776..d316d9b 100644 --- a/drivers/acpi/processor_core.c +++ b/drivers/acpi/processor_core.c @@ -71,6 +71,27 @@ static int map_lsapic_id(struct acpi_subtable_header *entry, return 0; }
+static int map_gic_id(struct acpi_subtable_header *entry,
int device_declaration, u32 acpi_id, int *apic_id)+{
- struct acpi_madt_generic_interrupt *gic =
(struct acpi_madt_generic_interrupt *)entry;- if (!(gic->flags & ACPI_MADT_ENABLED))
return -ENODEV;- /* In the GIC interrupt model, logical processors are
* required to have a Processor Device object in the DSDT,* so we should check device_declaration here*/- if (device_declaration && (gic->uid == acpi_id)) {
*apic_id = gic->gic_id;I have mentioned this earlier, it's not clear yet to me how does this work ? It needs more clarity in the form of comment here at-least as the ACPIv5.0 is also not so clear or explicit on how to handle this.
Yes, I noticed your comments and had a reply for that, after a long consideration for this, I would withdraw my previous comments before, please refer to the comments below.
Here you are expecting gic->uid = acpi_id which is fine, while acpi_map_cpuid matches apic_id with cpu_physical_id(which must be MPIDR in ARM{32,64}). The latter imposes restriction that gic->gic_id has to be MPIDR. Does that mean we are imposing restriction on GIC ID to be MPIDR ? If so please document it here and please explain the reason behind that choice.
On x86 and IA64, APIC/SAPIC ID is the hardware id of the logical processor, and UID is just a unique ID to identify the processor in DSDT, it can be any value, and even can be strings defined in ASL if I remember that correctly.
OK, but that's not the case on ARM{32,64}. My main concern here is if we don't make this definitions clear enough, the vendors might produce ACPI tables with whatever suits them and we may end up supporting them. Since we are starting with clean slate, we can avoid getting into such situations. I will be to be more elaborate this time.
I agree.
The GIC ID is referred as the local GIC’s hardware ID in ACPIv5.0. IIUC, since GICC is per-cpu entry, it has to GIC CPU interface ID.
Now how does it differ from MPIDR ? e.g. ARM TC2(multi cluster system) GIC ID MPIDR Comment 0 0x000 CA15_0 1 0x001 CA15_1 2 0x100 CA7_0 3 0x101 CA7_1 4 0x102 CA7_2
Yes, obvious different. I know GIC ID can matche the bit index of the associated processor in the distributor's GICD_ITARGETSR register, and it a clear statement in GICv1/GICv2, my question is that is this consistent in GICv3/v4 too? this will have some impact on the code implementation.
For GICv3/v4, the only way you can match a CPU with its local redistributor is by using the CPU MPIDR. The GIC CPU ID is an implementation choice that may not exist (it doesn't in a distributed implementation), so anything that relies on a GIC CPU ID is broken for GICv3.
So that's the broken part, it seems that GIC ID is useless both in GICv1/v2 and GICv3/v4 if it represents GIC CPU interface ID, the only reliable one is the MPIDR.
I agree UID should be MPIDR for future usage, so how about this solution:
+static int map_gic_id(struct acpi_subtable_header *entry, + int device_declaration, u32 acpi_id, int *apic_id) +{ + struct acpi_madt_generic_interrupt *gic = + (struct acpi_madt_generic_interrupt *)entry; + + if (!(gic->flags & ACPI_MADT_ENABLED)) + return -ENODEV; + + /* In the GIC interrupt model, logical processors are + * required to have a Processor Device object in the DSDT, + * so we should check device_declaration here + */ + if (device_declaration && (gic->uid == acpi_id)) { /* * this is the special case for ARM/ARM64, gic->uid * should be MPIDR which represents the CPU hardware * id, so use gic->uid instead of gic->gic_id here * to get the physical processor ID. (...) */ + *apic_id = gic->uid; + return 0; + } + + return -EINVAL; +} +
Thanks Hanjun