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

From: Scott Wood <[email-masked]>
Date: Tue, 15 Sep 2015 23:13:52 -0500

On Tue, 2015-09-15 at 22:18 -0500, Wang Dongsheng-B40534 wrote:
> Hi Scott,
> 
> > -----Original Message-----
> > From: Wang Dongsheng-B40534
> > Sent: Wednesday, September 16, 2015 10:44 AM
> > To: Wood Scott-B07421; Tang Yuantian-B29983
> > Cc: [email-masked]; [email-masked];
> > [email-masked]; [email-masked]; 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; [email-masked]; linuxppc-
> > > [email-masked]; [email-masked];
> > > [email-masked];
> > > 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 <[email-masked]>
> > > > > Cc: [email-masked]; [email-masked];
> > > > > [email-masked]; [email-masked]; Wang
> > > > > robh+Huan-
> > > > > B18965 <[email-masked]>; Jin Zhengxiong-R64188
> > > > > <[email-masked]>; Zhao Chenhui-B35336
> > > > > <[email-masked]>; Tang Yuantian-B29983
> > > > > <[email-masked]>
> > > > > 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: [email-masked]; [email-masked];
> > > > > > > [email-masked]; [email-masked]; 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: [email-masked];
> > > > > > > > > [email-masked];
> > > > > > > > > [email-masked]; [email-masked];
> > > > > > > > > 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@e2000{
>                 compatible = "fsl,t4240-rcpm", "fsl,qoriq-rcpm-2.0";
>                 reg = <0xe2000 0x1000>;
> +               fsl,rcpm-wakeup-cell-num = <2>;
>         };

OK, though "fsl,#rcpm-wakeup-cells" would be more idiomatic.

Also s/number of cell/number of cells/

-Scott