Re: [PATCH for-5.0 6/8] acpi: cpuhp: spec: add typical usecases

[Laszlo Ersek <lersek@redhat.com>]

On 12/04/19 18:05, Igor Mammedov wrote:
> Document work-flows for
>   * finding a CPU with pending 'insert/remove' event
>   * enumerating present and possible CPUs
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> ---
>  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".
> 

Nice!

I suggest unindenting the entire new text, to the leftmost column
(column#0) in the text file. Otherwise "Typical usecases" falls under
the scope of "write access".

With that:

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks!
Laszlo