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

On Tue, 2015-09-15 at 22:18 -0500, Wang Dongsheng-B40534 wrote:

Hi Scott,

quoted

-----Original Message-----
From: Wang Dongsheng-B40534
Sent: Wednesday, September 16, 2015 10:44 AM
To: Wood Scott-B07421; Tang Yuantian-B29983
Cc: devicetree@vger.kernel.org; linuxppc-dev@lists.ozlabs.org;
robh+dt@kernel.org; linux-arm-kernel@lists.infradead.org; Wang Huan-
B18965; Jin
Zhengxiong-R64188; Zhao Chenhui-B35336
Subject: RE: [PATCH v2 1/2] fsl: Add binding for RCPM

quoted

-----Original Message-----
From: Wood Scott-B07421
Sent: Wednesday, September 16, 2015 10:38 AM
To: Tang Yuantian-B29983
Cc: Wang Dongsheng-B40534; devicetree@vger.kernel.org; linuxppc-
dev@lists.ozlabs.org; robh+dt@kernel.org;
linux-arm-kernel@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:

quoted

quoted

-----Original Message-----
From: Wood Scott-B07421
Sent: Wednesday, September 16, 2015 10:32 AM
To: Wang Dongsheng-B40534 <redacted>
Cc: devicetree@vger.kernel.org; linuxppc-dev@lists.ozlabs.org;
robh+dt@kernel.org; linux-arm-kernel@lists.infradead.org; Wang
robh+Huan-
B18965 [off-list ref]; Jin Zhengxiong-R64188
[off-list ref]; Zhao Chenhui-B35336
[off-list ref]; Tang Yuantian-B29983
[off-list ref]
Subject: Re: [PATCH v2 1/2] fsl: Add binding for RCPM

On Tue, 2015-09-15 at 21:30 -0500, Wang Dongsheng-B40534 wrote:

quoted

Hi Scott,

quoted

-----Original Message-----
From: Wood Scott-B07421
Sent: Wednesday, September 16, 2015 10:19 AM
To: Wang Dongsheng-B40534
Cc: devicetree@vger.kernel.org; linuxppc-dev@lists.ozlabs.org;
robh+dt@kernel.org; linux-arm-kernel@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:

quoted

Hi Scott,

quoted

-----Original Message-----
From: Wood Scott-B07421
Sent: Wednesday, September 16, 2015 7:57 AM
To: Wang Dongsheng-B40534
Cc: devicetree@vger.kernel.org;
linuxppc-dev@lists.ozlabs.org;
robh+dt@kernel.org; linux-arm-kernel@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:

quoted

+* 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.

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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