linux-kernel - Re: [PATCH 1/3] ACPI: PCC: Add PCC shared memory region command and status bitfields

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Date:   Thu, 28 Sep 2023 11:49:25 +0800
From:   "lihuisong (C)" <lihuisong@...wei.com>
To:     Sudeep Holla <sudeep.holla@....com>
CC:     <linux-hwmon@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-i2c@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Andi Shyti <andi.shyti@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>, <lihuisong@...wei.com>
Subject: Re: [PATCH 1/3] ACPI: PCC: Add PCC shared memory region command and
 status bitfields


在 2023/9/27 21:59, Sudeep Holla 写道:
> On Wed, Sep 27, 2023 at 10:07:15AM +0800, lihuisong (C) wrote:
>> Hi Sudeep,
>>
>> 在 2023/9/26 20:28, Sudeep Holla 写道:
>>> Define the common macros to use when referring to various bitfields in
>>> the PCC generic communications channel command and status fields.
>> Can you define the bit0 macros in the "flags" for Extended PCC Subspace
>> Shared Memory Region?
> Sure I will take a look and include it in v2 if applicable.
Thanks
>
>>> Currently different drivers that need to use these bitfields have defined
>>> these locally. This common macro is intended to consolidate and replace
>>> those.
>>>
>>> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
>>> ---
>>>    include/acpi/pcc.h | 11 +++++++++++
>>>    1 file changed, 11 insertions(+)
>>>
>>> diff --git a/include/acpi/pcc.h b/include/acpi/pcc.h
>>> index 73e806fe7ce7..66d9934c2ee4 100644
>>> --- a/include/acpi/pcc.h
>>> +++ b/include/acpi/pcc.h
>>> @@ -18,7 +18,18 @@ struct pcc_mbox_chan {
>>>    	u16 min_turnaround_time;
>>>    };
>>> +/* Generic Communications Channel Shared Memory Region */
>>> +#define PCC_SIGNATURE			0x50424300
>> Why is this signature 0x50424300?
> It is as per the specification.
>
>> In ACPI spec, this signature is all 0x50434303.
> No, not exactly. It is just an example.
> The PCC signature - The signature of a subspace is computed by a bitwise-or
> of the value 0x50434300 with the subspace ID. For example, subspace 3 has
> signature 0x50434303
Sorry for my mistake. I know this.
I mean, why doesn't the following macro follow spec and define this 
signature as 0x504*3*430.
"#define PCC_SIGNATURE **0x504*2*4300*"*
Because it seems that all version of ACPI spec is 0x5043430.
>
> And I see the driver you mentioned(drivers/soc/hisilicon/kunpeng_hccs.c)
> is doing the right thing. I am bit confused as why you being the author
> of the driver are now confused.
I used 0x50424300 instead of 0x50424300 according to the spec.
>