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

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Message-ID: <20230928111152.cctl3m5rwtopyg2g@bogus>
Date:   Thu, 28 Sep 2023 12:11:52 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     "lihuisong (C)" <lihuisong@...wei.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>
Subject: Re: [PATCH 1/3] ACPI: PCC: Add PCC shared memory region command and
 status bitfields

On Thu, Sep 28, 2023 at 11:49:25AM +0800, lihuisong (C) wrote:
> 
> 在 2023/9/27 21:59, Sudeep Holla 写道:
> > On Wed, Sep 27, 2023 at 10:07:15AM +0800, lihuisong (C) wrote:

[...]

> > > > +/* 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.

Sorry my mistake. Stupidly the existing drivers have it wrong and I just
copied them without paying much attention. I will fix it up. It must be
0x50434300 instead of 0x50424300. If you have no other comments, can you
please ack v2 patch 4/4 changing soc kunpeng_hccs driver. I will fixup
the PCC_SIGNATURE and send it as part of my PR to Rafael.

Refer [1] for the change in PCC_SIGNATURE, sorry for missing the point. I
was confident that the existing code is correct :), but I am wrong.

-- 
Regards,
Sudeep

[1] https://git.kernel.org/sudeep.holla/l/pcc_defines