linux-kernel - RE: [v3,3/3] Documentation: dt: binding: fsl: Add 'fsl,ippdexpcr-alt-addr' property

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Message-ID: <AM0PR04MB66762594DDFC6E5B00BD103C8F870@AM0PR04MB6676.eurprd04.prod.outlook.com>
Date:   Wed, 25 Sep 2019 03:26:08 +0000
From:   Leo Li <leoyang.li@....com>
To:     Biwen Li <biwen.li@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        Ran Wang <ran.wang_1@....com>
CC:     "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [v3,3/3] Documentation: dt: binding: fsl: Add
 'fsl,ippdexpcr-alt-addr' property



> -----Original Message-----
> From: Biwen Li
> Sent: Tuesday, September 24, 2019 10:13 PM
> To: Leo Li <leoyang.li@....com>; shawnguo@...nel.org;
> robh+dt@...nel.org; mark.rutland@....com; Ran Wang
> <ran.wang_1@....com>
> Cc: linuxppc-dev@...ts.ozlabs.org; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org; devicetree@...r.kernel.org
> Subject: RE: [v3,3/3] Documentation: dt: binding: fsl: Add 'fsl,ippdexpcr-alt-
> addr' property
> 
> > >
> > > The 'fsl,ippdexpcr-alt-addr' property is used to handle an errata
> > > A-008646 on LS1021A
> > >
> > > Signed-off-by: Biwen Li <biwen.li@....com>
> > > ---
> > > Change in v3:
> > > 	- rename property name
> > > 	  fsl,rcpm-scfg -> fsl,ippdexpcr-alt-addr
> > >
> > > Change in v2:
> > > 	- update desc of the property 'fsl,rcpm-scfg'
> > >
> > >  Documentation/devicetree/bindings/soc/fsl/rcpm.txt | 14
> > > ++++++++++++++
> > >  1 file changed, 14 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/soc/fsl/rcpm.txt
> > > b/Documentation/devicetree/bindings/soc/fsl/rcpm.txt
> > > index 5a33619d881d..157dcf6da17c 100644
> > > --- a/Documentation/devicetree/bindings/soc/fsl/rcpm.txt
> > > +++ b/Documentation/devicetree/bindings/soc/fsl/rcpm.txt
> > > @@ -34,6 +34,11 @@ Chassis Version		Example Chips
> > >  Optional properties:
> > >   - little-endian : RCPM register block is Little Endian. Without it RCPM
> > >     will be Big Endian (default case).
> > > + - fsl,ippdexpcr-alt-addr : Must add the property for SoC LS1021A,
> >
> > You probably should mention this is related to a hardware issue on
> > LS1021a and only needed on LS1021a.
> Okay, got it, thanks, I will add this in v4.
> >
> > > +   Must include n + 1 entries (n = #fsl,rcpm-wakeup-cells, such as:
> > > +   #fsl,rcpm-wakeup-cells equal to 2, then must include 2 + 1 entries).
> >
> > #fsl,rcpm-wakeup-cells is the number of IPPDEXPCR registers on an SoC.
> > However you are defining an offset to scfg registers here.  Why these
> > two are related?  The length here should actually be related to the
> > #address-cells of the soc/.  But since this is only needed for LS1021, you can
> just make it 3.
> I need set the value of IPPDEXPCR resgiters from ftm_alarm0 device
> node(fsl,rcpm-wakeup = <&rcpm 0x0 0x20000000>;
> 0x0 is a value for IPPDEXPCR0, 0x20000000 is a value for IPPDEXPCR1).
> But because of the hardware issue on LS1021A, I need store the value of
> IPPDEXPCR registers to an alt address. So I defining an offset to scfg registers,
> then RCPM driver get an abosolute address from offset,  RCPM driver write
> the value of IPPDEXPCR registers to these abosolute addresses(backup the
> value of IPPDEXPCR registers).

I understand what you are trying to do.  The problem is that the new fsl,ippdexpcr-alt-addr property contains a phandle and an offset.  The size of it shouldn't be related to #fsl,rcpm-wakeup-cells.

> >
> > > +   The first entry must be a link to the SCFG device node.
> > > +   The non-first entry must be offset of registers of SCFG.
> > >
> > >  Example:
> > >  The RCPM node for T4240:
> > > @@ -43,6 +48,15 @@ The RCPM node for T4240:
> > >  		#fsl,rcpm-wakeup-cells = <2>;
> > >  	};
> > >
> > > +The RCPM node for LS1021A:
> > > +	rcpm: rcpm@...2140 {
> > > +		compatible = "fsl,ls1021a-rcpm", "fsl,qoriq-rcpm-2.1+";
> > > +		reg = <0x0 0x1ee2140 0x0 0x8>;
> > > +		#fsl,rcpm-wakeup-cells = <2>;
> > > +		fsl,ippdexpcr-alt-addr = <&scfg 0x0 0x51c>; /*
> > > SCFG_SPARECR8 */
> > > +	};
> > > +
> > > +
> > >  * Freescale RCPM Wakeup Source Device Tree Bindings
> > >  -------------------------------------------
> > >  Required fsl,rcpm-wakeup property should be added to a device node
> > > if the device
> > > --
> > > 2.17.1