linux-kernel - RE: [PATCH v4 3/7] dt-bindings: dma: rz-dmac: Document RZ/V2H(P) family of SoCs

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Message-ID:
 <TYCPR01MB12093A1002C4F7D7B989D10C4C2CD2@TYCPR01MB12093.jpnprd01.prod.outlook.com>
Date: Thu, 27 Feb 2025 18:16:27 +0000
From: Fabrizio Castro <fabrizio.castro.jz@...esas.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
CC: Vinod Koul <vkoul@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Magnus
 Damm <magnus.damm@...il.com>, Biju Das <biju.das.jz@...renesas.com>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: RE: [PATCH v4 3/7] dt-bindings: dma: rz-dmac: Document RZ/V2H(P)
 family of SoCs

Hi Geert,

Thanks for your feedback!

> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: 24 February 2025 12:44
> Subject: Re: [PATCH v4 3/7] dt-bindings: dma: rz-dmac: Document RZ/V2H(P) family of SoCs
> 
> Hi Fabrizio,
> 
> On Thu, 20 Feb 2025 at 16:01, Fabrizio Castro
> <fabrizio.castro.jz@...esas.com> wrote:
> > Document the Renesas RZ/V2H(P) family of SoCs DMAC block.
> > The Renesas RZ/V2H(P) DMAC is very similar to the one found on the
> > Renesas RZ/G2L family of SoCs, but there are some differences:
> > * It only uses one register area
> > * It only uses one clock
> > * It only uses one reset
> > * Instead of using MID/IRD it uses REQ NO/ACK NO
> > * It is connected to the Interrupt Control Unit (ICU)
> >
> > Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@...esas.com>
> 
> > v1->v2:
> > * Removed RZ/V2H DMAC example.
> > * Improved the readability of the `if` statement.
> 
> Thanks for the update!
> 
> > --- a/Documentation/devicetree/bindings/dma/renesas,rz-dmac.yaml
> > +++ b/Documentation/devicetree/bindings/dma/renesas,rz-dmac.yaml
> > @@ -61,14 +66,22 @@ properties:
> >    '#dma-cells':
> >      const: 1
> >      description:
> > -      The cell specifies the encoded MID/RID values of the DMAC port
> > -      connected to the DMA client and the slave channel configuration
> > -      parameters.
> > +      For the RZ/A1H, RZ/Five, RZ/G2{L,LC,UL}, RZ/V2L, and RZ/G3S SoCs, the cell
> > +      specifies the encoded MID/RID values of the DMAC port connected to the
> > +      DMA client and the slave channel configuration parameters.
> >        bits[0:9] - Specifies MID/RID value
> >        bit[10] - Specifies DMA request high enable (HIEN)
> >        bit[11] - Specifies DMA request detection type (LVL)
> >        bits[12:14] - Specifies DMAACK output mode (AM)
> >        bit[15] - Specifies Transfer Mode (TM)
> > +      For the RZ/V2H(P) SoC the cell specifies the REQ NO, the ACK NO, and the
> > +      slave channel configuration parameters.
> > +      bits[0:9] - Specifies the REQ NO
> 
> So REQ_NO is the new name for MID/RID.

It's certainly similar. I would say that REQ_NO + ACK_NO is the new MID_RID.

> 
> > +      bits[10:16] - Specifies the ACK NO
> 
> This is a new field.
> However, it is not clear to me which value to specify here, and if this
> is a hardware property at all, and thus needs to be specified in DT?

It is a HW property. The value to set can be found in Table 4.6-27 from
the HW User Manual, column "Ack No".

> 
> > +      bit[17] - Specifies DMA request high enable (HIEN)
> > +      bit[18] - Specifies DMA request detection type (LVL)
> > +      bits[19:21] - Specifies DMAACK output mode (AM)
> > +      bit[22] - Specifies Transfer Mode (TM)
> 
> These are the same as on other RZ SoCs.
> So wouldn't it be simpler to move ACK NO to the end (iff you need it
> in DT), so the rest of the layout stays the same as on other RZ SoCs?

I can certainly do that.

Thanks!

Fab

> 
> The rest LGTM.
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds