linux-kernel - Re: [PATCH v12 2/5] arm64: dts: ti: k3-am625-sk: Add M4F remoteproc node

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Message-ID: <20241004112637.nc2qcquiuwdhdrye@thirteen>
Date: Fri, 4 Oct 2024 06:26:37 -0500
From: Nishanth Menon <nm@...com>
To: Bryan Brattlof <bb@...com>
CC: Andrew Davis <afd@...com>, Vignesh Raghavendra <vigneshr@...com>,
        Tero
 Kristo <kristo@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v12 2/5] arm64: dts: ti: k3-am625-sk: Add M4F remoteproc
 node

On 16:06-20241003, Bryan Brattlof wrote:
> Hi Andrew!
> 
> On October  3, 2024 thus sayeth Andrew Davis:
> > From: Hari Nagalla <hnagalla@...com>
> > 
> > The AM62x SoCs of the TI K3 family have a Cortex M4F core in the MCU
> > domain. This core can be used by non safety applications as a remote
> > processor. When used as a remote processor with virtio/rpmessage IPC,
> > two carveout reserved memory nodes are needed. The first region is used
> > as a DMA pool for the rproc device, and the second region will furnish
> > the static carveout regions for the firmware memory.
> > 
> > The current carveout addresses and sizes are defined statically for
> > each rproc device. The M4F processor does not have an MMU, and as such
> > requires the exact memory used by the firmware to be set-aside.
> > 
> > Signed-off-by: Hari Nagalla <hnagalla@...com>
> > Signed-off-by: Andrew Davis <afd@...com>
> > ---
> >  .../arm64/boot/dts/ti/k3-am62x-sk-common.dtsi | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> > 
> > diff --git a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
> > index 44ff67b6bf1e4..6957b3e44c82f 100644
> > --- a/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
> > +++ b/arch/arm64/boot/dts/ti/k3-am62x-sk-common.dtsi
> > @@ -56,6 +56,18 @@ linux,cma {
> >  			linux,cma-default;
> >  		};
> >  
> > +		mcu_m4fss_dma_memory_region: m4f-dma-memory@...00000 {
> > +			compatible = "shared-dma-pool";
> > +			reg = <0x00 0x9cb00000 0x00 0x100000>;
> > +			no-map;
> > +		};
> > +
> > +		mcu_m4fss_memory_region: m4f-memory@...00000 {
> > +			compatible = "shared-dma-pool";
> > +			reg = <0x00 0x9cc00000 0x00 0xe00000>;
> > +			no-map;
> > +		};
> > +
> 
> The only issue I have here is this takes away memory from people who do 
> not use these firmware or causes them to work around this patch if they 
> choose to have different carveouts.

They can define their own overlays.

> 
> Would an overlay be appropriate for this?

Why is this any different from existing boards? Are you suggesting a
change for all existing boards as well?

-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D