[PATCH v2 1/2] fsl: Add binding for RCPM

[Wang Dongsheng]

Hi Scott,

> -----Original Message-----
> From: Wang Dongsheng-B40534
> Sent: Wednesday, September 16, 2015 10:44 AM
> To: Wood Scott-B07421; Tang Yuantian-B29983
> Cc: devicetree at vger.kernel.org; linuxppc-dev at lists.ozlabs.org;
> robh+dt at kernel.org; linux-arm-kernel at lists.infradead.org; Wang Huan-B18965; Jin
> Zhengxiong-R64188; Zhao Chenhui-B35336
> Subject: RE: [PATCH v2 1/2] fsl: Add binding for RCPM
> 
> 
> 
> > -----Original Message-----
> > From: Wood Scott-B07421
> > Sent: Wednesday, September 16, 2015 10:38 AM
> > To: Tang Yuantian-B29983
> > Cc: Wang Dongsheng-B40534; devicetree at vger.kernel.org; linuxppc-
> > dev at lists.ozlabs.org; robh+dt at kernel.org;
> > linux-arm-kernel at lists.infradead.org;
> > Wang Huan-B18965; Jin Zhengxiong-R64188; Zhao Chenhui-B35336
> > Subject: Re: [PATCH v2 1/2] fsl: Add binding for RCPM
> >
> > On Tue, 2015-09-15 at 21:35 -0500, Tang Yuantian-B29983 wrote:
> > >
> > > > -----Original Message-----
> > > > From: Wood Scott-B07421
> > > > Sent: Wednesday, September 16, 2015 10:32 AM
> > > > To: Wang Dongsheng-B40534 <Dongsheng.Wang at freescale.com>
> > > > Cc: devicetree at vger.kernel.org; linuxppc-dev at lists.ozlabs.org;
> > > > robh+dt at kernel.org; linux-arm-kernel at lists.infradead.org; Wang
> > > > robh+Huan-
> > > > B18965 <alison.wang at freescale.com>; Jin Zhengxiong-R64188
> > > > <Jason.Jin at freescale.com>; Zhao Chenhui-B35336
> > > > <chenhui.zhao at freescale.com>; Tang Yuantian-B29983
> > > > <Yuantian.Tang at freescale.com>
> > > > Subject: Re: [PATCH v2 1/2] fsl: Add binding for RCPM
> > > >
> > > > On Tue, 2015-09-15 at 21:30 -0500, Wang Dongsheng-B40534 wrote:
> > > > > Hi Scott,
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Wood Scott-B07421
> > > > > > Sent: Wednesday, September 16, 2015 10:19 AM
> > > > > > To: Wang Dongsheng-B40534
> > > > > > Cc: devicetree at vger.kernel.org; linuxppc-dev at lists.ozlabs.org;
> > > > > > robh+dt at kernel.org; linux-arm-kernel at lists.infradead.org; Wang
> > > > > > robh+Huan-
> > > > > > B18965; Jin
> > > > > > Zhengxiong-R64188; Zhao Chenhui-B35336; Tang Yuantian-B29983
> > > > > > Subject: Re: [PATCH v2 1/2] fsl: Add binding for RCPM
> > > > > >
> > > > > > On Tue, 2015-09-15 at 21:15 -0500, Wang Dongsheng-B40534 wrote:
> > > > > > > Hi Scott,
> > > > > > >
> > > > > > > > -----Original Message-----
> > > > > > > > From: Wood Scott-B07421
> > > > > > > > Sent: Wednesday, September 16, 2015 7:57 AM
> > > > > > > > To: Wang Dongsheng-B40534
> > > > > > > > Cc: devicetree at vger.kernel.org;
> > > > > > > > linuxppc-dev at lists.ozlabs.org;
> > > > > > > > robh+dt at kernel.org; linux-arm-kernel at lists.infradead.org;
> > > > > > > > robh+Wang
> > > > > > > > robh+Huan-
> > > > > > > > B18965; Jin
> > > > > > > > Zhengxiong-R64188; Zhao Chenhui-B35336; Tang
> > > > > > > > Yuantian-B29983
> > > > > > > > Subject: Re: [PATCH v2 1/2] fsl: Add binding for RCPM
> > > > > > > >
> > > > > > > > On Tue, 2015-09-15 at 16:55 +0800, Dongsheng Wang wrote:
> > > > > > > > > +* Freescale RCPM Wakeup Source Device Tree Bindings
> > > > > > > > > +-------------------------------------------
> > > > > > > > > +Required rcpm-wakeup property should be added to a
> > > > > > > > > +device node if the
> > > > > > > > > device
> > > > > > > > > +can be used as a wakeup source.
> > > > > > > > > +
> > > > > > > > > +  - rcpm-wakeup: The value of the property consists of 3 cells.
> > > > > > > > > + The
> > > > > > > > > first
> > > > > > > > > cell
> > > > > > > > > +     is a pointer to the rcpm node, the second cell is
> > > > > > > > > + the bit mask
> > > > > > > > > that
> > > > > > > > > +     should be set in IPPDEXPCR0, and the last cell is
> > > > > > > > > + for
> > > > > > > > > IPPDEXPCR1.
> > > > > > > > > +     Note: If the platform has no IPPDEXPCR1 register,
> > > > > > > > > + put a zero
> > > > > > > > > here.
> > > > > > > >
> > > > > > > > What if a future platform has more than two of these registers?
> > > > > > >
> > > > > > > Those registers are only used for wakeup device, we have a
> > > > > > > lot of available bit for feature. For example, In LS1021a
> > > > > > > platform only 7bits has used in the registers, and 57bits is
> reserved.
> > > > > >
> > > > > > Still, it'd be better to for the rcpm node to advertise the
> > > > > > number of cells it expects.
> > > > >
> > > > > For the foreseeable future it should be enough to use, even if
> > > > > not enough to use in the future at that time we can update the binding.
> > > >
> > > > That's the whole point.  Device tree is stable ABI.  Updating it
> > > > later to not be fixed to two cells would be a lot harder than
> > > > getting it right from the beginning.  Putting the number of cells
> > > > in the phandle target is a standard device tree idiom.
> > > >
> > > I agree with you. But what's the point a SOC has more than 64 wakeup source?
> >
> > I don't know.  Hardware people do strange things sometimes.  They
> > might not want to reuse bits they once used for something on some
> > other chip, or they might have some encoding scheme in mind that
> > results in the bits not being packed as tightly as possible, or there
> > may be some big array of similar devices...
> >
> > What's the point of skipping this part of the phandle-plus-arguments idiom?
> 
> Fine, I will add a property in rcpm node to describe the number of register.
> 

How about the following modify? If okay for you I will fix in next version.

Required properites:
   - reg : Offset and length of the register set of RCPM block.
+  - fsl,rcpm-wakeup-cell-num : The number of cell in rcpm-wakeup property.

        rcpm: global-utilities at e2000 {
                compatible = "fsl,t4240-rcpm", "fsl,qoriq-rcpm-2.0";
                reg = <0xe2000 0x1000>;
+               fsl,rcpm-wakeup-cell-num = <2>;
        };

Regards,
-Dongsheng