linux-kernel - Re: [PATCH V7 3/6] i2c: qup: Transfer each i2c_msg in i2c

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Message-ID: <20160204200903.GE1958@tetsubishi>
Date:	Thu, 4 Feb 2016 21:09:03 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Sricharan <sricharan@...eaurora.org>
Cc:	devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	agross@...eaurora.org, linux-kernel@...r.kernel.org,
	linux-i2c@...r.kernel.org, iivanov@...sol.com,
	galak@...eaurora.org, dmaengine@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, andy.gross@...aro.org,
	ntelkar@...eaurora.org, architt@...eaurora.org
Subject: Re: [PATCH V7 3/6] i2c: qup: Transfer each i2c_msg in i2c_msgs
 without a stop bit

Hi,

> Ah, so what I meant above is there is no 'STOP' bit between each msg in
> i2c_msgs,
> but 'REAPEATED_START' still holds true.  We are sending 'START' bit for each
> msg.
> So these is how each msg in i2c_msg is sent,
>
> |------MSG1--------|-----MSG2---------|------MSG3------------|
>
>   |START|DATA|------|START|DATA|---|START|DATA|STOP|
>
> If my commit text does not make this clear, I  can reword that ?

OK, now this looks to me perfectly fine: A number of *messages*
concatenated into one *transfer* by repeated start. That's the way it
should be.

So, I'd simply remove these words:

"The QUP i2c hardware has no way to inform that there should not be a
'STOP' at the end of transaction. The only way to implement this is to
coalesce all the i2c_msg in i2c_msgs in to one transaction and transfer
them."

This sounded like the HW needed a special handling, so I was under the
impression REP_START was broken. However, unless I misunderstood
something again, this now sounds like the standard case and we can keep
the commit message simple. If you are okay with that, I can update it
here, no need to resend.

Thanks,

   Wolfram

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