linux-kernel - Re: [PATCH 5/8] riscv: dts: spacemit: Add dma bus and PDMA node for K1 SoC

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Message-ID: <aEwyaQF6W7hXNC6N@jean.localdomain>
Date: Fri, 13 Jun 2025 22:15:05 +0800
From: Ze Huang <huangze@...t.edu.cn>
To: Vivian Wang <uwu@...m.page>, Guodong Xu <guodong@...cstar.com>,
	vkoul@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, dlan@...too.org, paul.walmsley@...ive.com,
	palmer@...belt.com, aou@...s.berkeley.edu, alex@...ti.fr,
	p.zabel@...gutronix.de, drew@...7.com,
	emil.renner.berthing@...onical.com, inochiama@...il.com,
	geert+renesas@...der.be, tglx@...utronix.de,
	hal.feng@...rfivetech.com, joel@....id.au, duje.mihanovic@...le.hr,
	Ze Huang <huangze@...t.edu.cn>
Cc: elder@...cstar.com, dmaengine@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev
Subject: Re: [PATCH 5/8] riscv: dts: spacemit: Add dma bus and PDMA node for
 K1 SoC

On Fri, Jun 13, 2025 at 11:06:43AM +0800, Vivian Wang wrote:
> Hi Guodong,
> 
> On 6/11/25 20:57, Guodong Xu wrote:
> > <snip>
> >
> > -			status = "disabled";
> > +		dma_bus: bus@4 {
> > +			compatible = "simple-bus";
> > +			#address-cells = <2>;
> > +			#size-cells = <2>;
> > +			dma-ranges = <0x0 0x00000000 0x0 0x00000000 0x0 0x80000000>,
> > +				     <0x1 0x00000000 0x1 0x80000000 0x3 0x00000000>;
> > +			ranges;
> >  		};
> 
> Can the addition of dma_bus and movement of nodes under it be extracted
> into a separate patch, and ideally, taken up by Yixun Lan without going
> through dmaengine? Not specifically "dram_range4", but all of these
> translations affects many devices on the SoC, including ethernet and
> USB3. See:
> 
> https://lore.kernel.org/all/20250526-b4-k1-dwc3-v3-v4-2-63e4e525e5cb@whut.edu.cn/
> https://lore.kernel.org/all/20250613-net-k1-emac-v1-0-cc6f9e510667@iscas.ac.cn/
> 
> (I haven't put eth{0,1} under dma_bus5 because in 6.16-rc1 there is
> none, but ideally we should fix this.)
> 
> DMA address translation does not depend on PDMA. It would be best if we
> get all the possible dma-ranges buses handled in one place, instead of
> everyone moving nodes around.

Agree

> 
> @Ze Huang: This affects your "MBUS" changes as well. Please take a look,
> thanks.

Thanks for reminding. I would drop MBUS and follow the "dma_bus" approach.

> 
> >  
> >  		gpio: gpio@...19000 {
> > @@ -792,3 +693,124 @@ pwm19: pwm@...22c00 {
> >  		};
> >  	};
> >  };
> > +
> > +&dma_bus {
> >
> > <snip>