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

-----Original Message-----
From: Kumar Gala [mailto:galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org]
Sent: Friday, August 15, 2014 10:26 AM
To: Basu Arnab-B45036
Cc: Mark Rutland; Sharma Bhupesh-B45370; arnd-r2nGTMty4D4@public.gmane.org; Catalin Marinas;
devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org; Will Deacon; Yoder Stuart-B08248;
grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org; linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.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-KZfg59tc24xl57MIdRCFDg@public.gmane.org wrote:

quoted

quoted

quoted

+	cpus {
+		#address-cells = <2>;
+		#size-cells = <0>;
+
+		/* We have 4 clusters having 2 Cortex-A57 cores each */
+		cpu@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
property and drop it from here.

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

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

Thanks,
Stuart


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