linux-kernel - Re: [PATCH v5 2/3] I2C: mediatek: Add driver for MediaTek I2C controller

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Date:	Tue, 31 Mar 2015 19:52:34 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Eddie Huang <eddie.huang@...iatek.com>
Cc:	Mark Rutland <mark.rutland@....com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Doug Anderson <dianders@...omium.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	David Box <david.e.box@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Jean Delvare <jdelvare@...e.de>,
	Xudong Chen (陈旭东) 
	<Xudong.Chen@...iatek.com>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	Pawel Moll <pawel.moll@....com>,
	Liguo Zhang (张立国) 
	<Liguo.Zhang@...iatek.com>, Wei Yan <sledge.yanwei@...wei.com>,
	Bjorn Andersson <bjorn.andersson@...ymobile.com>,
	Uwe Kleine-Konig <u.kleine-koenig@...gutronix.de>,
	Neelesh Gupta <neelegup@...ux.vnet.ibm.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Beniamino Galvani <b.galvani@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	"linux-mediatek@...ts.infradead.org" 
	<linux-mediatek@...ts.infradead.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	srv_heupstream <srv_heupstream@...iatek.com>,
	Anders Berg <anders.berg@...gotech.com>,
	Jim Cromie <jim.cromie@...il.com>,
	Simon Glass <sjg@...omium.org>,
	Max Schwarz <max.schwarz@...ine.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sascha Hauer <kernel@...gutronix.de>,
	Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH v5 2/3] I2C: mediatek: Add driver for MediaTek I2C
 controller

On Tue, Mar 31, 2015 at 07:50:58PM +0800, Eddie Huang wrote:
> Hi Sascha,
> 
> On Tue, 2015-03-31 at 15:08 +0800, Eddie Huang wrote:
> > Hi Sascha,
> > 
> > > > > speed <= 400000 here to make this more obvious?
> > > > There are two cases, not only speed<=400000, but I2C_MASTER_WRRD. I tend
> > > > to keep it.
> > >
> > > Still it looks strange. You only ever write this default value to the
> > > register. Putting this register write under an if() seems bogus since
> > > the same value will be in the register the next time this code is
> > > executed. It looks like you should move this register write to some
> > > initialization function.
> > OK, move to mtk_i2c_init_hw function
> > 
> Sorry for my negligence. Write-then-read (I2C_MASTER_WRRD) decides
> according to each I2C transfer, so I still need to judge whether set
> I2C_CONTROL_RS and DELAY_LEN here. Other control setting can move to
> init function.

You need to decide whether you have to set the I2C_CONTROL_RS bit, but
you don't need to write the same value to the DELAY_LEN register each
time. It won't change under your hood.

Sascha

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