linux-kernel - Re: [PATCH v5 1/3] i2c: aspeed: Add slave

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Date:   Tue, 30 Nov 2021 11:02:59 +0100
From:   Wolfram Sang <wsa@...nel.org>
To:     Quan Nguyen <quan@...amperecomputing.com>
Cc:     Corey Minyard <minyard@....org>, Rob Herring <robh+dt@...nel.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        openipmi-developer@...ts.sourceforge.net,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org,
        Open Source Submission <patches@...erecomputing.com>,
        Phong Vo <phong@...amperecomputing.com>,
        "Thang Q . Nguyen" <thang@...amperecomputing.com>
Subject: Re: [PATCH v5 1/3] i2c: aspeed: Add slave_enable() to toggle slave
 mode

Hi,

> Thanks Wolfram to help bring this up,

Sure thing! It would be sad to see this work bitrot.

> This driver was tested with Aspeed ast2500 and we have tried many way to
> avoid using slave_enable() to toggle slave mode but there is no progress.

I see. I also can't help you there. I have neither experience with nor
access to this HW.

> Our expectation is still to have this driver upstream'ed and I'm thinking
> about testing this driver on other HW and re-post the driver.

That sounds like a good plan.

> I have to admit that you are all right with the above comments. The fact is
> we still not be able to find any way to solve this differently. We don't own
> this HW and dont know what happen on this particular issue. The SCL clock
> stretching on this HW does not work as expected and the slave_enable() is
> the only solution for now. I hope if someone could help with the issue as
> well.

From this distance, it looks like HW access and a logic analyzer might
be helpful in understanding the behaviour. Pity that you don't own the
HW.

Good luck nonetheless!

   Wolfram


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