Date:   Mon, 29 Nov 2021 13:49:05 +0100
From:   Wolfram Sang <wsa@the-dreams.de>
To:     Kewei Xu <kewei.xu@mediatek.com>, matthias.bgg@gmail.com,
        robh+dt@kernel.org, linux-i2c@vger.kernel.org,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
        srv_heupstream@mediatek.com, leilk.liu@mediatek.com,
        qii.wang@mediatek.com, liguo.zhang@mediatek.com,
        caiyu.chen@mediatek.com, ot_daolong.zhu@mediatek.com,
        yuhan.wei@mediatek.com
Subject: Re: [PATCH v7 6/7] i2c: mediatek: Isolate speed setting via dts for
 special devices
Message-ID: <YaTMQQhENmJAIUk4@kunai>
Mail-Followup-To: Wolfram Sang <wsa@the-dreams.de>,
        Kewei Xu <kewei.xu@mediatek.com>, matthias.bgg@gmail.com,
        robh+dt@kernel.org, linux-i2c@vger.kernel.org,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
        srv_heupstream@mediatek.com, leilk.liu@mediatek.com,
        qii.wang@mediatek.com, liguo.zhang@mediatek.com,
        caiyu.chen@mediatek.com, ot_daolong.zhu@mediatek.com,
        yuhan.wei@mediatek.com
References: <20210917101416.20760-1-kewei.xu@mediatek.com>
 <20210917101416.20760-7-kewei.xu@mediatek.com>
 <YVf+83LdUEPjoLdI@kunai>
 <1891acec7f5c417f62081a8b10249b265df7ea62.camel@mediatek.com>
 <YWQYbaTIhud2QHNP@kunai>
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> > stretching. But if the slave device stretch the SCL line for too long
> > time, our design still cannot make tSU,STA/tHD,STA/tSU,STO meet spec.
>=20
> Isn't the new algorithm broken if it cannot support clock stretching?
> What was the problem of the old algorithm not meeting the spec?
>=20
> > However in the old (default) timing algorithm before the commit
> > be5ce0e97cc7 ("i2c: mediatek: Add i2c ac-timing adjust support"),
> > tSU,STA/tHD,STA/tSU,STO can meet spec. So we want to define a new
> > setting "default-adjust-timing" for using the old (default) timing
> > algorithm."
>=20
> What I still do not get: the old algorithm was able to handle clock
> stretching. Why can't you update the new one to handle clock stretching
> as well. I might be missing something, but what is it?

I am still interested. Especially in the last question. Is the last
question clear to you? I can explain some more otherwise.


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