linux-kernel - Re: [PATCH 7/8] ARM64: dts: amlogic: Extend GXBaby GIC node

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Date:	Tue, 1 Mar 2016 12:43:52 +0000
From:	Andre Przywara <andre.przywara@....com>
To:	Andreas Färber <afaerber@...e.de>,
	linux-meson@...glegroups.com
Cc:	Mark Rutland <mark.rutland@....com>,
	devicetree <devicetree@...r.kernel.org>,
	Matthias Brugger <mbrugger@...e.com>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Nicolas Saenz <nicolassaenzj@...il.com>,
	Will Deacon <will.deacon@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Kumar Gala <galak@...eaurora.org>,
	Carlo Caione <carlo@...one.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 7/8] ARM64: dts: amlogic: Extend GXBaby GIC node

Hi,

On 01/03/16 11:18, Andreas Färber wrote:
> Hi Andre,
> 
> Am 01.03.2016 um 12:01 schrieb Andre Przywara:
>> On 29/02/16 23:44, Andreas Färber wrote:
>>> Add GICH and GICV resources for HYP mode - guess based on other vendors.
>>
>> Do you know if the firmware allows the kernel to be entered in EL2
>> (which is the arm64 name for HYP)?
>> So can we run kvm?
>> If you have a booted kernel, can you grep for "EL2" and "kvm" in the dmesg?
> 
> I do not have a rootfs yet (MMC v5 patches by Carlo are still waiting
> for review), but with this change the KVM driver initializes okay - the
> purpose of this patch!
> 
>> Also you should merge this patch into 3/8, same for 8/8.
> 
> If people confirm this is generally or specifically for this SoC correct
> then sure. So far 3/8 seems a safe subset for lack of public documentation.

The GIC is an integral part of the SoC, so this clearly belongs in there.

>>> Signed-off-by: Andreas Färber <afaerber@...e.de>
>>> ---
>>>  arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi | 4 +++-

In general I was wondering if this naming is correct?
Shouldn't it be something with "s905" in it? Because this the SoC that
is driving all those hardware and the peripherals that you describe in
there are clearly within the SoC.
So something like meson-s905.dtsi or the like?

>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi b/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
>>> index 0ae089bd1806..5088ae3ff653 100644
>>> --- a/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
>>> +++ b/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
>>> @@ -117,7 +117,9 @@
>>>  		gic: interrupt-controller@...01000 {
>>>  			compatible = "arm,cortex-a15-gic", "arm,cortex-a9-gic";
>>
>> I think "arm,gic-400" is the name to use here these days, especially for
>> arm64.
> 
> I took what /proc/device-tree showed on Android and verified that this
> compatible is in use in mainline.

Some vendor Android kernel is not a good reference for mainline work ;-)
Better look at other DTs in arch/arm64/boot/dts.
You could keep "arm,cortex-a15-gic" in there if you care about
compatibility with older (vendor) kernels, but I guess there are other
issues which prevent this anyway, so you could drop this as well.

>>>  			reg = <0x0 0xc4301000 0 0x1000>,
>>> -			      <0x0 0xc4302000 0 0x0100>;
>>> +			      <0x0 0xc4302000 0 0x0100>,
>>
>> Please use 0x2000 for the size here. I guess this is really the GIC-400
>> from ARM, and in this case this is the right size, [1] is the reference
>> here. This will enable EOI mode 1 for KVM.
> 
> Will test later.
> 
> Is there any easy way to find out whether or not this is that GIC-400?

If you can read registers: GICD_IIDR and PIDRx have some info:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0471b/CHDIFAEE.html
So if your U-Boot for instance supports md, a dump of:
md.l c4301008 1
md.l c4301fd0 30

would help to identify the GIC.

Cheers,
Andre.

> 
> Thanks,
> Andreas
> 
>> [1]
>> http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0471b/CHDIFAEE.html
>>
>>> +			      <0x0 0xc4304000 0 0x2000>,
>>> +			      <0x0 0xc4306000 0 0x2000>;
>>>  			interrupt-controller;
>>>  			interrupts = <GIC_PPI 9
>>>  				(GIC_CPU_MASK_SIMPLE(8) | IRQ_TYPE_LEVEL_HIGH)>;
>