Subject: Re: [PATCH 4/8] arm64: dts: add NXP S32G2 support

From: Chester Lin <[email-masked]>
Date: Fri, 13 Aug 2021 11:28:04 +0800

On Thu, Aug 12, 2021 at 07:26:28PM +0200, Andreas Färber wrote:
> Hi Chester et al.,
> 
> On 05.08.21 08:54, Chester Lin wrote:
> > Add an initial dtsi file for generic SoC features of NXP S32G2.
> > 
> > Signed-off-by: Chester Lin <[email-masked]>
> > ---
> >  arch/arm64/boot/dts/freescale/s32g2.dtsi | 98 ++++++++++++++++++++++++
> >  1 file changed, 98 insertions(+)
> >  create mode 100644 arch/arm64/boot/dts/freescale/s32g2.dtsi
> > 
> > diff --git a/arch/arm64/boot/dts/freescale/s32g2.dtsi b/arch/arm64/boot/dts/freescale/s32g2.dtsi
> > new file mode 100644
> > index 000000000000..3321819c1a2d
> > --- /dev/null
> > +++ b/arch/arm64/boot/dts/freescale/s32g2.dtsi
> 
> Note: This DT is for running on the Cortex-A53 cores, but S32G2 also has
> Cortex-M7 cores. For Vybrid SoCs, DTs later got contributed to also run
> on its Cortex-M4 core:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/arch/arm/boot/dts/vf610.dtsi
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/arch/arm/boot/dts/vf500.dtsi
> vs.
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/arch/arm/boot/dts/vf610m4.dtsi
> 
> Should we plan for this in our file naming here and in following patches
> (e.g., s32g2-a53* vs. s32g2-m7*)? To me, a later concatenation of
> s32g274am7* would look awkward, and s32g274a-m7* would sort between -evb
> and -rdb2.
> 
> > @@ -0,0 +1,98 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
> > +/*
> 
>  * NXP S32G2 SoC family
>  *
> ?

Will add it.

> 
> @NXP: Are any models other than 274A in the queue that we should
> distinguish between s32g2.dtsi and s32g274a.dtsi here already?
> 
> > + * Copyright (c) 2021 SUSE LLC
> > + */
> > +
> > +#include <dt-bindings/interrupt-controller/arm-gic.h>
> > +
> > +/ {
> > +	compatible = "fsl,s32g2";
> > +	interrupt-parent = <&gic>;
> > +	#address-cells = <2>;
> > +	#size-cells = <2>;
> > +
> > +	cpus {
> > +		#address-cells = <1>;
> > +		#size-cells = <0>;
> > +
> > +		cpu0: cpu@0 {
> > +			device_type = "cpu";
> > +			compatible = "arm,cortex-a53";
> > +			reg = <0x0>;
> > +			enable-method = "psci";
> > +			next-level-cache = <&cluster0_l2>;
> > +		};
> > +
> > +		cpu1: cpu@1 {
> > +			device_type = "cpu";
> > +			compatible = "arm,cortex-a53";
> > +			reg = <0x1>;
> > +			enable-method = "psci";
> > +			next-level-cache = <&cluster0_l2>;
> > +		};
> > +
> > +		cpu2: cpu@100 {
> > +			device_type = "cpu";
> > +			compatible = "arm,cortex-a53";
> > +			reg = <0x100>;
> > +			enable-method = "psci";
> > +			next-level-cache = <&cluster1_l2>;
> > +		};
> > +
> > +		cpu3: cpu@101 {
> > +			device_type = "cpu";
> > +			compatible = "arm,cortex-a53";
> > +			reg = <0x101>;
> > +			enable-method = "psci";
> > +			next-level-cache = <&cluster1_l2>;
> > +		};
> > +
> > +		cluster0_l2: l2-cache0 {
> > +			compatible = "cache";
> > +		};
> > +
> > +		cluster1_l2: l2-cache1 {
> > +			compatible = "cache";
> > +		};
> > +	};
> > +
> > +	pmu {
> > +		compatible = "arm,cortex-a53-pmu";
> > +		interrupts = <GIC_PPI 7 IRQ_TYPE_LEVEL_HIGH>;
> 
> interrupt-affinity = <&cpu0>, <&cpu1>, <&cpu2>, <&cpu3>;

Actually I traced the pmu_parse_irqs() and found that this SoC never falls into
the pmu_has_irq_affinity() check because it's a percpu IRQ so the flow ends at
pmu_parse_percpu_irq(). But it looks good to me to have an interrupt-affinity
to indicate that each core has an associated PPI for PMU events as the binding
file has suggested.

> 
> > +	};
> > +
> > +	timer {
> > +		compatible = "arm,armv8-timer";
> > +		interrupts = <GIC_PPI 13 IRQ_TYPE_LEVEL_LOW>,
> > +			     <GIC_PPI 14 IRQ_TYPE_LEVEL_LOW>,
> > +			     <GIC_PPI 11 IRQ_TYPE_LEVEL_LOW>,
> > +			     <GIC_PPI 10 IRQ_TYPE_LEVEL_LOW>;
> > +	};
> > +
> > +	psci {
> > +		compatible = "arm,psci-1.0";
> > +		method = "smc";
> > +	};
> 
> Should we move this into a /firmware node, to group with future OP-TEE?
> 

So far I can only see a few examples [e.g. ti/k3-*] which add the psci node
into /firmware but logically we should do it.

> > +
> > +	soc {
> > +		compatible = "simple-bus";
> > +		interrupt-parent = <&gic>;
> 
> Duplicate, already set on root node.

Will remove it.

> 
> > +		#address-cells = <2>;
> > +		#size-cells = <2>;
> 
> Why? Does it have any peripherals that go beyond 32-bit space?
> For 64-bit Realtek platforms Rob had asked me to use 1, if possible.
> I do understand that for /memory nodes we do have high-memory addresses,
> so 2 for the root node looks correct.

Actually it's a limitation due to [PATCH 7/8] "arm64: dts: s32g2: add memory
nodes for evb and rdb2", which adds memory nodes to indicate maximum system
RAM size combined by two separated memory banks, and the second bank starts
from the offset 0x880000000 so that's why we need 64-bit address space here.
Please feel free to let me know if any suggestion.

> 
> > +
> 
> Please drop this white line.
> 

Will do.

> > +		ranges;
> 
> According to Rob, the /soc ranges should exclude any RAM ranges for
> safety reasons. Compare:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/arch/arm64/boot/dts/realtek/rtd129x.dtsi
> 
> If you're lacking the maximum RAM areas to carve out, NXP is in CC to
> help out :) and the EVB and RDB2 boards should give you starting numbers
> that could be enlarged later if needed.

I added memory nodes in [PATCH 7/8] "arm64: dts: s32g2: add memory nodes for
evb and rdb2" to describe maximum RAM areas, which are based on the information
we found in NXP BSP and boards.

@NXP: Please feel free to correct me if anything wrong, thanks.

> 
> > +
> > +		gic: interrupt-controller@50800000 {
> > +			compatible = "arm,gic-v3";
> > +			#interrupt-cells = <3>;
> > +			interrupt-controller;
> > +			reg = <0 0x50800000 0 0x10000>,
> > +			      <0 0x50880000 0 0x200000>,
> > +			      <0 0x50400000 0 0x2000>,
> > +			      <0 0x50410000 0 0x2000>,
> > +			      <0 0x50420000 0 0x2000>;
> 
> Please order reg after compatible by convention, and sort
> interrupt-controller or at least #interrupt-cells (applying to
> consumers) last, after the below one applying to this device itself.
> 

Will do.

> > +			interrupts = <GIC_PPI 9 (GIC_CPU_MASK_SIMPLE(4) |
> > +						 IRQ_TYPE_LEVEL_HIGH)>;
> > +		};
> 
> CC'ing Marc for additional GIC scrutiny, often the sizes are wrong.
> 

IIRC, gic-v3 shouldn't have this kind of interrupt specifier. It's my fault and
will fix it. Feel free to let me know if any suggestions.

> > +	};
> > +};
> 
> Thanks,
> Andreas
> 
> -- 
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> GF: Felix Imendörffer
> HRB 36809 (AG Nürnberg)
> 

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