linux-kernel - Re: [PATCH] soc: hisilicon: Support HCCS driver on Kunpeng SoC

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Message-ID: <db6c713c-f99c-fa3f-8d38-9a5d50889cc2@huawei.com>
Date:   Thu, 4 May 2023 21:16:16 +0800
From:   "lihuisong (C)" <lihuisong@...wei.com>
To:     Sudeep Holla <sudeep.holla@....com>
CC:     Arnd Bergmann <arnd@...db.de>,
        Bjorn Andersson <andersson@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Shawn Guo <shawnguo@...nel.org>,
        <linux-kernel@...r.kernel.org>, <soc@...nel.org>,
        <wanghuiqiang@...wei.com>, <tanxiaofei@...wei.com>,
        <liuyonglong@...wei.com>, <huangdaode@...wei.com>,
        <linux-acpi@...r.kernel.org>, Len Brown <lenb@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        <devicetree@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Subject: Re: [PATCH] soc: hisilicon: Support HCCS driver on Kunpeng SoC


在 2023/4/25 21:19, Sudeep Holla 写道:
> On Tue, Apr 25, 2023 at 09:00:31PM +0800, lihuisong (C) wrote:
>> For firmware, DSD way is simpler and easier to manage these virtual platform
>> devices, and it's an usual way in kernel.
> Any specific examples you are referring here. We had lots of debate when
> DSD was introduced. It must be used only when there is no standard ACPI
> way to achieve the same. But in this I don't (yet) think that is the case.
> Further "simplicity" is remotely not the reason why you must use DSD.
> So until you provide me technical reasons as why _CRS can't work, I
> have to NACK this approach. DSD in this case seems like pure hack.
>
>> Driver only needs to get a fixed value, like pcc-id and type, here.
>>
> Yes and _CRS is used to get similar such properties in ACPI. It includes
> normally MMIO and interrupts and since GAS supports PCC and _CRS can
> contain GAS, you must simply use that.
Hi Sudeep,

I'm tring to use CRS with GAS to report PCC channel ID and get other 
informations driver need by address.
I found a way to obtain the generic register information according to 
"Referencing the PCC address space" in ACPI spec.
And driver also get the PCC generic register information successfully.

But I don't know how to set and use the address in PCC register.
Where should this address come from?
It seems that ACPI spec is not very detailed about this.
Do you have any suggestions?

On the other hand, we think that System Memory space + method can also 
achieve above goal.
What do you think of that?

Best regards,
Huisong