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

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Message-ID: <5642165E.1080408@broadcom.com>
Date:	Tue, 10 Nov 2015 21:37:58 +0530
From:	Kapil Hali <kapilh@...adcom.com>
To:	Florian Fainelli <f.fainelli@...il.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>,
	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

Hi Florian,

On 11/8/2015 3:10 AM, Florian Fainelli wrote:
> 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.
> 
I overlooked this patch and didn't change the description. It is a physical
address of a register which holds the address of the secondary core's entry 
point.

>> +
>> +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"
>>
> 
> 

Thanks,
Kapil Hali

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