Commit 3a61c8db9d25 introduced CPHP_GET_CPU_ID_CMD command but
did not sufficiently described how to use it. Fix it by adding
missing command documentation and suggested work-flow to enumerate
possible architecture specific CPU IDs.
Fixes: 3a61c8db9d25 ("acpi: cpuhp: add CPHP_GET_CPU_ID_CMD command")
Signed-off-by: Igor Mammedov <[email protected]>
---
docs/specs/acpi_cpu_hotplug.txt | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt
index a8ce5e7..81b4534 100644
--- a/docs/specs/acpi_cpu_hotplug.txt
+++ b/docs/specs/acpi_cpu_hotplug.txt
@@ -94,6 +94,8 @@ write access:
register in QEMU
2: following writes to 'Command data' register set OST status
register in QEMU
+ 3: following reads from 'Command data' and 'Command data 2' return
+ architecture specific CPU ID value for currently selected CPU.
other values: reserved
[0x6-0x7] reserved
[0x8] Command data: (DWORD access)
@@ -147,3 +149,16 @@ Typical usecases:
11. Otherwise store 0x0 to the 'CPU selector' register, to put it
into a valid state and exit.
The iterator at this point equals "max_cpus".
+
+ - Enumerate present/non present CPUs architecture specific IDs
+ (in case of x86: ACPIC IDs)
+ 01: Use "Enumerate CPUs present/non present CPUs" to get max_cpus
+ 02: Store 0x3 in the 'Command field' register
+ 03: Set 'current cpu selector' iterator to 0x0
+ 04: Store the iterator to the 'CPU selector' register
+ 05: Read from registers 'Command data' and 'Command data 2' parts of ID,
+ combine them into ID like following:
+ 'Command data 2' << 32 | 'Command data'
+ and store pair 'current cpu selector' : ID for further processing
+ 06: Increment the iterator and if the iterator < max_cpus go to step 4
+ 07: Otherwise store 0x0 to the 'CPU selector' register and exit.
--
2.7.4
