linux-kernel - Re: [RESEND] i2c: mediatek: Get device clock-stretch time via dts

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Date:   Mon, 12 Apr 2021 20:03:14 +0800
From:   Qii Wang <qii.wang@...iatek.com>
To:     Wolfram Sang <wsa@...-dreams.de>
CC:     <matthias.bgg@...il.com>, <linux-i2c@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>, <leilk.liu@...iatek.com>
Subject: Re: [RESEND] i2c: mediatek: Get device clock-stretch time via dts

On Wed, 2021-04-07 at 20:19 +0200, Wolfram Sang wrote:
> > Due to clock stretch, our HW IP cannot meet the ac-timing
> > spec(tSU;STA,tSU;STO). 
> > There isn't a same delay for clock stretching, so we need pass a
> > parameter which can be found through measurement to meet most
> > conditions.
> 
> What about using this existing binding?
> 
> - i2c-scl-internal-delay-ns
>         Number of nanoseconds the IP core additionally needs to setup SCL.
> 

I can't see the relationship between "i2c-scl-falling-time-ns" and clock
stretching, is there a parameter related to clock stretching?
If you think both of them will affect the ac-timing of SCL, at this
point, "i2c-scl-falling-time-ns" maybe a good choice.