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Date:   Tue, 25 Apr 2023 11:30:40 +0100
From:   Sudeep Holla <sudeep.holla@arm.com>
To:     Arnd Bergmann <arnd@arndb.de>, Huisong Li <lihuisong@huawei.com>
Cc:     Bjorn Andersson <andersson@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Sudeep Holla <sudeep.holla@arm.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Shawn Guo <shawnguo@kernel.org>, linux-kernel@vger.kernel.org,
        soc@kernel.org, wanghuiqiang@huawei.com, tanxiaofei@huawei.com,
        liuyonglong@huawei.com, huangdaode@huawei.com,
        linux-acpi@vger.kernel.org, Len Brown <lenb@kernel.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        devicetree@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Subject: Re: [PATCH] soc: hisilicon: Support HCCS driver on Kunpeng SoC
Message-ID: <20230425103040.znv66k364ant6klq@bogus>
References: <20230424073020.4039-1-lihuisong@huawei.com>
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Thanks Arnd for cc-ing the ALKML.

On Mon, Apr 24, 2023 at 10:09:47AM +0200, Arnd Bergmann wrote:
> On Mon, Apr 24, 2023, at 09:30, Huisong Li wrote:

[...]

> > +
> > +static int hccs_get_device_property(struct hccs_dev *hdev)
> > +{
> > +	struct device *dev = hdev->dev;
> > +
> > +	if (device_property_read_u32(dev, "device-flags", &hdev->flags)) {
> > +		dev_err(hdev->dev, "no device-flags property.\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	if (device_property_read_u8(dev, "pcc-type", &hdev->type)) {
> > +		dev_err(hdev->dev, "no pcc-type property.\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	if (device_property_read_u32(dev, "pcc-chan-id", &hdev->chan_id)) {
> > +		dev_err(hdev->dev, "no pcc-channel property.\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	hdev->intr_mode = hccs_get_bit(hdev->flags, HCCS_DEV_FLAGS_INTR_B);
> > +	if (!hccs_dev_property_supported(hdev))
> > +		return -EOPNOTSUPP;
> > +
>
> Where are the device properties documented? I'm never quite sure how
> to handle these for ACPI-only drivers, since we don't normally have the
> bindings in Documentation/devicetree/bindings/, but it feels like there
> should be some properly reviewed document somewhere else.
>
> Adding ACPI and devicetree maintainers to Cc for clarification.

Why are these DSD style properties added here ? Why can't we just make
use of _CRS with Generic Address Structure(GAS) register entry for each
of the PCC channel which eliminates the need of "pcc-chan-id". The type
must be deduced from the order in the list of _CRS if needed. I don't
quite understand what magic the flags contain here to provide any info
there.

--
Regards,
Sudeep