From: "Sricharan" <sricharan@codeaurora.org>
To: "'Wolfram Sang'" <wsa@the-dreams.de>
Cc: <devicetree@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
<agross@codeaurora.org>, <linux-kernel@vger.kernel.org>,
<linux-i2c@vger.kernel.org>, <iivanov@mm-sol.com>,
<galak@codeaurora.org>, <dmaengine@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>, <andy.gross@linaro.org>,
<ntelkar@codeaurora.org>, <architt@codeaurora.org>
Subject: RE: [PATCH V7 3/6] i2c: qup: Transfer each i2c_msg in i2c_msgs without a stop bit
Date: Thu, 28 Jan 2016 10:27:05 +0530 [thread overview]
Message-ID: <001401d15988$59f6dcf0$0de496d0$@codeaurora.org> (raw)
In-Reply-To: <20160124112915.GA1775@katana>
Hi Wolfram,
> -----Original Message-----
> From: Wolfram Sang [mailto:wsa@the-dreams.de]
> Sent: Sunday, January 24, 2016 4:59 PM
> To: Sricharan R
> Cc: devicetree@vger.kernel.org; linux-arm-msm@vger.kernel.org;
> agross@codeaurora.org; linux-kernel@vger.kernel.org; linux-
> i2c@vger.kernel.org; iivanov@mm-sol.com; galak@codeaurora.org;
> dmaengine@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> andy.gross@linaro.org; ntelkar@codeaurora.org; architt@codeaurora.org
> Subject: Re: [PATCH V7 3/6] i2c: qup: Transfer each i2c_msg in i2c_msgs
> without a stop bit
>
> Hi,
>
> > "If this is the last message in a group, it is followed by a STOP.
> > Otherwise it is followed by the next @i2c_msg transaction segment,
> > beginning with a (repeated) START"
>
> This is correct.
>
> > So the expectation is that there is no 'STOP' bit inbetween individual
> > i2c_msg segments with repeated 'START'. 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. Adding the support for
> the same.
>
> So, there will not be a REP_START condition on the bus? I am sorry to say
that
> I can't accept this. A REP_START is a REP_START and nothing else. There
are
> devices which will get confused if there is no real REP_START condition.
>
> Without knowing the HW in detail, can't you implement I2C_M_NOSTART
> and let the touchscreen driver use it via regmap? That would be the proper
> way (from what I understand).
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 ?
Regards,
Sricharan
next prev parent reply other threads:[~2016-01-28 4:57 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-19 10:02 [PATCH V7 0/6] i2c: qup: Add support for v2 tags and bam dma Sricharan R
2016-01-19 10:02 ` [PATCH V7 1/6] i2c: qup: Change qup_wait_writeready function to use for all timeouts Sricharan R
2016-02-12 18:37 ` Wolfram Sang
2016-01-19 10:02 ` [PATCH V7 2/6] i2c: qup: Add V2 tags support Sricharan R
2016-02-12 18:37 ` Wolfram Sang
2016-01-19 10:02 ` [PATCH V7 3/6] i2c: qup: Transfer each i2c_msg in i2c_msgs without a stop bit Sricharan R
2016-01-24 11:29 ` Wolfram Sang
2016-01-28 4:57 ` Sricharan [this message]
2016-02-04 20:09 ` Wolfram Sang
2016-02-05 8:00 ` Sricharan
2016-02-12 18:38 ` Wolfram Sang
2016-01-19 10:02 ` [PATCH V7 4/6] i2c: qup: Add bam dma capabilities Sricharan R
2016-02-12 18:37 ` Wolfram Sang
2016-02-12 18:42 ` Wolfram Sang
2016-02-13 6:58 ` Sricharan
2016-02-22 12:24 ` Sricharan
2016-02-22 12:32 ` Wolfram Sang
2016-02-22 13:41 ` Sricharan
2016-01-19 10:02 ` [PATCH V7 5/6] dts: msm8974: Add blsp2_bam dma node Sricharan R
2016-03-25 23:17 ` Bjorn Andersson
2016-03-26 2:26 ` Andy Gross
2016-03-28 12:59 ` Sricharan
2016-01-19 10:02 ` [PATCH V7 6/6] dts: msm8974: Add dma channels for blsp2_i2c1 node Sricharan R
2016-01-19 10:14 ` [PATCH V7 0/6] i2c: qup: Add support for v2 tags and bam dma Sricharan
2016-01-24 11:33 ` Wolfram Sang
2016-01-28 5:27 ` Sricharan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='001401d15988$59f6dcf0$0de496d0$@codeaurora.org' \
--to=sricharan@codeaurora.org \
--cc=agross@codeaurora.org \
--cc=andy.gross@linaro.org \
--cc=architt@codeaurora.org \
--cc=devicetree@vger.kernel.org \
--cc=dmaengine@vger.kernel.org \
--cc=galak@codeaurora.org \
--cc=iivanov@mm-sol.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-arm-msm@vger.kernel.org \
--cc=linux-i2c@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=ntelkar@codeaurora.org \
--cc=wsa@the-dreams.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).