Hi Wolfram, > -----Original Message----- > From: Wolfram Sang [mailto:wsa@xxxxxxxxxxxxx] > Sent: Sunday, January 24, 2016 4:59 PM > To: Sricharan R > Cc: devicetree@xxxxxxxxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx; > agross@xxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux- > i2c@xxxxxxxxxxxxxxx; iivanov@xxxxxxxxxx; galak@xxxxxxxxxxxxxx; > dmaengine@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > andy.gross@xxxxxxxxxx; ntelkar@xxxxxxxxxxxxxx; architt@xxxxxxxxxxxxxx > 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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
