linux-kernel - RE: [EXT] Re: [PATCH 1/2] i2c: imx: I2C Driver doesn't consider I2C_IPGCLK

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Date:   Mon, 6 May 2019 07:46:49 +0000
From:   Chuanhua Han <chuanhua.han@....com>
To:     Sascha Hauer <s.hauer@...gutronix.de>
CC:     "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Leo Li <leoyang.li@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "festevam@...il.com" <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "wsa+renesas@...g-engineering.com" <wsa+renesas@...g-engineering.com>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "eha@...f.com" <eha@...f.com>,
        "linux@...pel-privat.de" <linux@...pel-privat.de>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        "peda@...ntia.se" <peda@...ntia.se>,
        Sumit Batra <sumit.batra@....com>
Subject: RE: [EXT] Re: [PATCH 1/2] i2c: imx: I2C Driver doesn't consider
 I2C_IPGCLK_SEL RCW bit when using ls1046a SoC



> -----Original Message-----
> From: Sascha Hauer <s.hauer@...gutronix.de>
> Sent: 2019年5月6日 15:38
> To: Chuanhua Han <chuanhua.han@....com>
> Cc: shawnguo@...nel.org; Leo Li <leoyang.li@....com>; robh+dt@...nel.org;
> mark.rutland@....com; linux-kernel@...r.kernel.org;
> linux-i2c@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> devicetree@...r.kernel.org; festevam@...il.com; dl-linux-imx
> <linux-imx@....com>; wsa+renesas@...g-engineering.com;
> u.kleine-koenig@...gutronix.de; eha@...f.com; linux@...pel-privat.de;
> l.stach@...gutronix.de; peda@...ntia.se; Sumit Batra
> <sumit.batra@....com>
> Subject: Re: [EXT] Re: [PATCH 1/2] i2c: imx: I2C Driver doesn't consider
> I2C_IPGCLK_SEL RCW bit when using ls1046a SoC
> 
> Caution: EXT Email
> 
> On Sat, May 04, 2019 at 09:28:48AM +0000, Chuanhua Han wrote:
> >
> >
> > > -----Original Message-----
> > > From: Sascha Hauer <s.hauer@...gutronix.de>
> > > Sent: 2019年4月30日 20:51
> > > To: Chuanhua Han <chuanhua.han@....com>
> > > Cc: shawnguo@...nel.org; Leo Li <leoyang.li@....com>;
> > > robh+dt@...nel.org; mark.rutland@....com;
> > > linux-kernel@...r.kernel.org; linux-i2c@...r.kernel.org;
> > > linux-arm-kernel@...ts.infradead.org;
> > > devicetree@...r.kernel.org; festevam@...il.com; dl-linux-imx
> > > <linux-imx@....com>; wsa+renesas@...g-engineering.com;
> > > u.kleine-koenig@...gutronix.de; eha@...f.com;
> > > linux@...pel-privat.de; l.stach@...gutronix.de; peda@...ntia.se;
> > > Sumit Batra <sumit.batra@....com>
> > > Subject: [EXT] Re: [PATCH 1/2] i2c: imx: I2C Driver doesn't consider
> > > I2C_IPGCLK_SEL RCW bit when using ls1046a SoC
> > >
> > > Caution: EXT Email
> > >
> > > On Tue, Apr 30, 2019 at 12:47:18PM +0800, Chuanhua Han wrote:
> > > > The current kernel driver does not consider I2C_IPGCLK_SEL (424
> > > > bit of
> > > > RCW) in deciding  i2c_clk_rate in function i2c_imx_set_clk() { 0
> > > > Platform clock/4, 1 Platform clock/2}.
> > > >
> > > > When using ls1046a SoC, this populates incorrect value in IBFD
> > > > register if I2C_IPGCLK_SEL = 0, which generates half of the desired Clock.
> > > >
> > > > Therefore, if ls1046a SoC is used, we need to set the i2c clock
> > > > according to the corresponding RCW.
> > >
> > > So the clock driver reports the wrong clock. Please fix the clock driver then.
> > No, this is a problem with the i2c driver. It is not a problem with
> > the clock driver, so the i2c driver needs to be modified.
> 
> So how does this RCW bit get evaluated? According to the reference manual
> only one clock goes to the i2c module (described as 1/2 Platform
> Clock) and the i2c module only takes one clock. So it seems there must be a /2
> divider somewhere, either in each i2c module or somewhere outside. Can your
> IC guys tell you where it is?
> 
> One reason I suggested the clock driver is that the clock driver contains SoC
> specific code already, so it should be easier to integrate there.
OK, I will see that it can be qualified in the clock driver.
> 
> Sascha
> 
> 
> --
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