[PATCH 4/6] arm64: Add DTS support for FSL's LS2085A SoC

-----Original Message-----
From: Kumar Gala [mailto:galak at codeaurora.org]
Sent: Friday, August 15, 2014 10:44 AM
To: Yoder Stuart-B08248
Cc: Basu Arnab-B45036; Mark Rutland; Sharma Bhupesh-B45370; arnd at arndb.de;
Catalin Marinas; Will Deacon; grant.likely at secretlab.ca; linux-arm-
kernel at lists.infradead.org; devicetree at vger.kernel.org
Subject: Re: [PATCH 4/6] arm64: Add DTS support for FSL's LS2085A SoC


On Aug 15, 2014, at 10:41 AM, Stuart Yoder [off-list ref] wrote:

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-----Original Message-----
From: Kumar Gala [mailto:galak at codeaurora.org]
Sent: Friday, August 15, 2014 10:26 AM
To: Basu Arnab-B45036
Cc: Mark Rutland; Sharma Bhupesh-B45370; arnd at arndb.de; Catalin Marinas;
devicetree-discuss at lists.ozlabs.org; Will Deacon; Yoder Stuart-B08248;
grant.likely at secretlab.ca; linux-arm-kernel at lists.infradead.org
Subject: Re: [PATCH 4/6] arm64: Add DTS support for FSL's LS2085A SoC


On Aug 15, 2014, at 10:21 AM, arnab.basu at freescale.com wrote:

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+	cpus {
+		#address-cells = <2>;
+		#size-cells = <0>;
+
+		/* We have 4 clusters having 2 Cortex-A57 cores each */
+		cpu at 0 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = <0x0 0x0>;
+			enable-method = "spin-table";
+			cpu-release-addr = <0x0 0x8000fff8>;
+		};

I would strongly recommend having a unique cpu-release-addr for each CPU.

This is more of a place holder, we intend to patch this address from U-Boot
and use individual release addresses for each CPU.

If you are going to patch it in u-boot, than why not just have u-boot add

the

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property and drop it from here.

If you intend to keep it here, than make <0x0 0x0> and add a comment that

says

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u-boot will fill it out

As I said to Mark re: the comment on having different release addresses
per CPU, we are just following existing practice from the existing
arch/arm64 device trees:
  apm-storm.dtsi
  foundation-v8.dts
  rtsm_ve-aemv8a.dts

I think one of the reasons the cpu-release-addr is not 0x0 is that
UEFI had(?)/has(?) limited ability to do device tree fix ups.  It's
not a problem at all in u-boot, but there is some reason all
existing device trees have the same hardcoded address for all
CPUs.

Are you guys planning on supporting UEFI on this platform?

Yes.

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So we want to do the standard/conventional thing here that will
allow are device trees to be used in more than u-boot.

Well, I think the guys would say the standard thing is to move to PSCI.

Agree.  That is our plan.  But it looks like at this point in
time all the device tree have a common denominator spin table
mechanim that gets updated/overriden if PSCI is supported.

Stuart