linux-kernel - Re: [PATCH 05/12] arm64: dts: Add I2C nodes for Hi3660

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Message-ID: <a45b3ab7-4f77-be0a-6382-a94e43fd512e@linux.intel.com>
Date:   Wed, 24 May 2017 11:31:10 +0300
From:   Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:     zhangfei <zhangfei.gao@...aro.org>, Rob Herring <robh@...nel.org>
Cc:     Guodong Xu <guodong.xu@...aro.org>, Wei Xu <xuwei5@...ilicon.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Chen Feng <puck.chen@...ilicon.com>,
        Jiancheng Xue <xuejiancheng@...ilicon.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 05/12] arm64: dts: Add I2C nodes for Hi3660

On 05/24/2017 05:34 AM, zhangfei wrote:
> Rob suggest add something like "hisilicon,hi3660-dw-i2c" as well.
> "The problem is dw-i2c does not give any clue as to what the
> configuration or version of the IP is.
> Is that fully discoverable with version/capability registers? If not
> then you need a specific compatible.
> Generally when we have not required them, it ends up being a problem
> later on."
>
Some features are discoverable from DW_IC_COMP_PARAM_1, 
DW_IC_COMP_VERSION and DW_IC_COMP_TYPE registers. Although my 
specification does not document what's inside of DW_IC_COMP_VERSION and 
DW_IC_COMP_TYPE but code is using them.

>
> While Documentation/devicetree/bindings/i2c/i2c-designware.txt
> compatible : should be "snps,designware-i2c"
>
> Besides, on Hikey960,
> [    3.822353] dw_readl(dev, DW_IC_COMP_VERSION)=0x3132302a
> [    3.827763] dw_readl(dev, DW_IC_COMP_TYPE)=0x44570140
> Are these two registers enough to distinguish version etc?
>
I've seen DW_IC_COMP_VERSION being 0x3131352a or 0x3132312a in our 
platforms. DW_IC_COMP_TYPE has the same value what you are seeing.

-- 
Jarkko