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[PATCH for-5.0 6/8] acpi: cpuhp: spec: add typical usecases
From: |
Igor Mammedov |
Subject: |
[PATCH for-5.0 6/8] acpi: cpuhp: spec: add typical usecases |
Date: |
Wed, 4 Dec 2019 18:05:45 +0100 |
Document work-flows for
* finding a CPU with pending 'insert/remove' event
* enumerating present and possible CPUs
Signed-off-by: Igor Mammedov <address@hidden>
---
docs/specs/acpi_cpu_hotplug.txt | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt
index f3c552d..58c16c6 100644
--- a/docs/specs/acpi_cpu_hotplug.txt
+++ b/docs/specs/acpi_cpu_hotplug.txt
@@ -64,6 +64,7 @@ write access:
[0x0-0x3] CPU selector: (DWORD access)
selects active CPU device. All following accesses to other
registers will read/store data from/to selected CPU.
+ Valid values: [0 .. max_cpus)
[0x4] CPU device control fields: (1 byte access)
bits:
0: reserved, OSPM must clear it before writing to register.
@@ -96,3 +97,31 @@ write access:
ACPI_DEVICE_OST QMP event from QEMU to external applications
with current values of OST event and status registers.
other values: reserved
+
+ Typical usecases:
+ - Get a cpu with pending event
+ 1. Store 0x0 to the 'CPU selector' register.
+ 2. Store 0x0 to the 'Command field' register.
+ 3. Read the 'CPU device status fields' register.
+ 4. If both bit#1 and bit#2 are clear in the value read, there is no
CPU
+ with a pending event and selected CPU remains unchanged.
+ 5. Otherwise, read the 'Command data' register. The value read is the
+ selector of the CPU with the pending event (which is already
+ selected).
+
+ - Enumerate CPUs present/non present CPUs
+ 01. Set the present CPU count to 0.
+ 02. Set the iterator to 0.
+ 03. Store 0x0 to the 'CPU selector' register, to ensure that it's in
+ a valid state and that access to other registers won't be
ignored.
+ 04. Store 0x0 to the 'Command field' register to make 'Command data'
+ register return 'CPU selector' value of selected CPU
+ 05. Read the 'CPU device status fields' register.
+ 06. If bit#0 is set, increment the present CPU count.
+ 07. Increment the iterator.
+ 08. Store the iterator to the 'CPU selector' register.
+ 09. Read the 'Command data' register.
+ 10. If the value read is not zero, goto 05.
+ 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".
--
2.7.4
- [PATCH for-5.0 0/8] q35: CPU hotplug with secure boot, part 1+2, Igor Mammedov, 2019/12/04
- [PATCH for-5.0 3/8] acpi: cpuhp: spec: clarify 'CPU selector' register usage and endianness, Igor Mammedov, 2019/12/04
- [PATCH for-5.0 6/8] acpi: cpuhp: spec: add typical usecases,
Igor Mammedov <=
- [PATCH for-5.0 5/8] acpi: cpuhp: spec: clarify store into 'Command data' when 'Command field' == 0, Igor Mammedov, 2019/12/04
- [PATCH for-5.0 7/8] acpi: cpuhp: add CPHP_GET_CPU_ID_CMD command, Igor Mammedov, 2019/12/04
[PATCH for-5.0 8/8] acpi: cpuhp: spec: document procedure for enabling modern CPU hotplug, Igor Mammedov, 2019/12/04