linux-kernel - Re: [PATCH v2] i2c: mediatek: disable zero-length transfers for mt8183

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Date:   Fri, 30 Aug 2019 15:08:42 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Hsin-Yi Wang <hsinyi@...omium.org>
Cc:     Yingjoe Chen <yingjoe.chen@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Qii Wang <qii.wang@...iatek.com>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Jun Gao <jun.gao@...iatek.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Alexandru M Stan <amstan@...omium.org>
Subject: Re: [PATCH v2] i2c: mediatek: disable zero-length transfers for
 mt8183

On Thu, Aug 22, 2019 at 05:45:17PM +0800, Hsin-Yi Wang wrote:
> When doing i2cdetect quick write mode, we would get transfer
> error ENOMEM, and i2cdetect shows there's no device at the address.
> Quoting from mt8183 datasheet, the number of transfers to be
> transferred in one transaction should be set to bigger than 1,
> so we should forbid zero-length transfer and update functionality.
> 
> Incorrect return:
> localhost ~ # i2cdetect -q -y 0
>      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00:          -- -- -- -- -- -- -- -- -- -- -- -- --
> 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 70: -- -- -- -- -- -- -- --
> 
> After this patch:
> localhost ~ #  i2cdetect -q -y 0
> Error: Can't use SMBus Quick Write command on this bus
> 
> localhost ~ #  i2cdetect -y 0
> Warning: Can't use SMBus Quick Write command, will skip some addresses
>      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00:
> 10:
> 20:
> 30: -- -- -- -- -- -- -- --
> 40:
> 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 60:
> 70:

Thanks for providing these test results. Much appreciated. To shorten
the commit log a little, I removed them before applying, though.

> 
> Reported-by: Alexandru M Stan <amstan@...omium.org>
> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>

Applied to for-next, thanks!


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