linux-kernel - Re: [PATCH 4/5] dt-bindings: i2c: Add Mediatek MT8183 i2c binding

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Date:   Thu, 13 Dec 2018 17:32:27 +0800
From:   Qii Wang <qii.wang@...iatek.com>
To:     Wolfram Sang <wsa@...-dreams.de>
CC:     <linux-i2c@...r.kernel.org>, <devicetree@...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>,
        <ryder.lee@...iatek.com>
Subject: Re: [PATCH 4/5] dt-bindings: i2c: Add Mediatek MT8183 i2c binding

On Tue, 2018-12-11 at 21:29 +0100, Wolfram Sang wrote:
> > +  - ch-offset: base reg offset for multi-user.
> 
> What is "multi-user"? Why can't you add this offset to the reg-property
> directly?
> 

Thanks for your comment.
There are 3 channel in one MT8183 I3C controller, and every channel can
be used as an I2C controller.
Take the following diagram as example:
If use I3C channels as I2C bus,
1. CH-A/B/C offset are different;
2. If use CH-B or CH-A as I2C, they must config registers which's
address are in CH-A.
 ____________________________________
|     ________                       |
|    |        |<--- offset:0x00      |
|    |  CH-A  |                      |
|    |________|                      |
|    |        |<--- offset:0x100     |
|    |  CH-B  |                      |
|    |________|                      |
|    |        |<--- offset:0x200     |
|    |  CH-C  |                      |
|    |________|                      |
|____________________________________|
        one I3C controller               

Because of CH-B/CH-C depend on CH-A's register, it can't add offset to
reg-property directly.

MT8183 doesn't need to support muti-user according to the latest project
information, and I'll remove this feature from patches.

> > +  - mediatek,share-i3c: i3c controller can share i2c function.
> 
> Please explain in more detail? Is this an I3C controller?
> 

Yes, it is a i3c controller, and it is compatible with i2c. I only use
the feature of i2c, so I need a flag to do some extra settings.