linux-kernel - Re: [PATCH v3 1/4] dt-bindings: add SMP enable-method for Broadcom NSP

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Date:	Sat, 7 Nov 2015 13:40:23 -0800
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Kapil Hali <kapilh@...adcom.com>, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Ray Jui <rjui@...adcom.com>,
	Scott Branden <sbranden@...adcom.com>,
	Jon Mason <jonmason@...adcom.com>
Cc:	Gregory Fong <gregory.0xf0@...il.com>, Lee Jones <lee@...nel.org>,
	Hauke Mehrtens <hauke@...ke-m.de>,
	Heiko Stuebner <heiko@...ech.de>,
	Kever Yang <kever.yang@...k-chips.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Olof Johansson <olof@...om.net>,
	Paul Walmsley <paul@...an.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Chen-Yu Tsai <wens@...e.org>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH v3 1/4] dt-bindings: add SMP enable-method for Broadcom
 NSP

Le 06/11/2015 13:11, Kapil Hali a écrit :
> Add a compatible string "brcm,bcm-nsp-smp" for Broadcom's
> Northstar Plus CPU to the 32-bit ARM CPU device tree binding
> documentation file and create a new binding documentation for
> Northstar Plus CPU.
> 
> Signed-off-by: Kapil Hali <kapilh@...adcom.com>
> ---
>  .../bindings/arm/bcm/brcm,nsp-cpu-method.txt       | 36 ++++++++++++++++++++++
>  Documentation/devicetree/bindings/arm/cpus.txt     |  1 +
>  2 files changed, 37 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/bcm/brcm,nsp-cpu-method.txt
> 
> diff --git a/Documentation/devicetree/bindings/arm/bcm/brcm,nsp-cpu-method.txt b/Documentation/devicetree/bindings/arm/bcm/brcm,nsp-cpu-method.txt
> new file mode 100644
> index 0000000..8506da7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/bcm/brcm,nsp-cpu-method.txt
> @@ -0,0 +1,36 @@
> +Broadcom Northstar Plus SoC CPU Enable Method
> +---------------------------------------------
> +This binding defines the enable method used for starting secondary
> +CPUs in the following Broadcom SoCs:
> +  BCM58522, BCM58525, BCM58535, BCM58622, BCM58623, BCM58625, BCM88312
> +
> +The enable method is specified by defining the following required
> +properties in the "cpus" device tree node:
> +  - enable-method = "brcm,bcm-nsp-smp";
> +  - secondary-boot-reg = <...>;
> +
> +The secondary-boot-reg property is a u32 value that specifies the
> +physical address of the register used to request the ROM holding pen
> +code release a secondary CPU.

Is it really how the ROM code is implemented, as a pen holding/release
mechanism (which sounds like how this was implemented previously in the
kernel actually) or should this be described in a more generic way as
the physical address of the register where the secondary CPUs reset
vector address must be written to? Or something along these lines.

> +
> +Example:
> +	cpus {
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +		enable-method = "brcm,bcm-nsp-smp";

Just a nit, but if NSP and NS are sharing the same mechanism, would not
a more "NS-centric" property be more appropriate because NS came before NSP?

> +		secondary-boot-reg = <0xffff042c>;
> +
> +		cpu0: cpu@0 {
> +			device_type = "cpu";
> +			compatible = "arm,cortex-a9";
> +			next-level-cache = <&L2>;
> +			reg = <0>;
> +		};
> +
> +		cpu1: cpu@1 {
> +			device_type = "cpu";
> +			compatible = "arm,cortex-a9";
> +			next-level-cache = <&L2>;
> +			reg = <1>;
> +		};
> +	};
> diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt
> index 91e6e5c..6abe3f3 100644
> --- a/Documentation/devicetree/bindings/arm/cpus.txt
> +++ b/Documentation/devicetree/bindings/arm/cpus.txt
> @@ -191,6 +191,7 @@ nodes to be present and contain the properties described below.
>  			    "allwinner,sun8i-a23"
>  			    "arm,psci"
>  			    "brcm,brahma-b15"
> +			    "brcm,bcm-nsp-smp"
>  			    "marvell,armada-375-smp"
>  			    "marvell,armada-380-smp"
>  			    "marvell,armada-390-smp"
> 


-- 
Florian
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