From: Wolfram Sang <wsa@the-dreams.de>
To: Qii Wang <qii.wang@mediatek.com>
Cc: matthias.bgg@gmail.com, linux-i2c@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
Subject: Re: [RESEND] i2c: mediatek: Get device clock-stretch time via dts
Date: Tue, 13 Apr 2021 22:17:40 +0200 [thread overview]
Message-ID: <20210413201740.GC2751@kunai> (raw)
In-Reply-To: <1618228994.32225.3.camel@mhfsdcap03>
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On Mon, Apr 12, 2021 at 08:03:14PM +0800, Qii Wang wrote:
> 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?
( you wrote "i2c-scl-falling-time-ns" above, didn't you mean
"i2c-scl-internal-delay-ns" instead? )
Not yet, and I wonder if there can be one. In I2C (not SMBus), devices
are allowed to stretch the clock as long as they want, so what should be
specified here?
I suggesteed "internal-delay" because AFAIU your hardware needs this
delay to be able to cope with 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.
Do you mean "i2c-scl-falling-time-ns" or "i2c-scl-internal-delay-ns"?
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next prev parent reply other threads:[~2021-04-13 20:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-13 8:04 [RESEND] i2c: mediatek: Get device clock-stretch time via dts qii.wang
2021-03-18 11:23 ` Wolfram Sang
2021-04-06 19:48 ` Wolfram Sang
2021-04-07 12:15 ` Qii Wang
2021-04-07 18:19 ` Wolfram Sang
2021-04-12 12:03 ` Qii Wang
2021-04-13 20:17 ` Wolfram Sang [this message]
2021-04-14 1:37 ` Qii Wang
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