RE: [PATCH 1/5] dt-bindings: dma: Document RZ/G2L bindings

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Hi Geert,

Thanks for the feedback.

> -----Original Message-----
> Subject: Re: [PATCH 1/5] dt-bindings: dma: Document RZ/G2L bindings
> 
> Hi Biju,
> 
> On Fri, Jun 11, 2021 at 1:36 PM Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> wrote:
> > Document RZ/G2L DMAC bindings.
> >
> > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> > Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> 
> Thanks for your patch!
> 
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/dma/renesas,rz-dmac.yaml
> > @@ -0,0 +1,132 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) %YAML 1.2
> > +---
> > +$id:
> > +https://jpn01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevi
> > +cetree.org%2Fschemas%2Fdma%2Frenesas%2Crz-dmac.yaml%23&amp;data=04%7C
> > +01%7Cbiju.das.jz%40bp.renesas.com%7C4b547e10cbe64b6f4d8508d92f2da0c0%
> > +7C53d82571da1947e49cb4625a166a4a2a%7C0%7C0%7C637592695286846809%7CUnk
> > +nown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haW
> > +wiLCJXVCI6Mn0%3D%7C1000&amp;sdata=5Jh%2FxPaia5ZOY0CrViQCcrNtzuDejp8wo
> > +Nrx9iO0ht8%3D&amp;reserved=0
> > +$schema:
> > +https://jpn01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevi
> > +cetree.org%2Fmeta-schemas%2Fcore.yaml%23&amp;data=04%7C01%7Cbiju.das.
> > +jz%40bp.renesas.com%7C4b547e10cbe64b6f4d8508d92f2da0c0%7C53d82571da19
> > +47e49cb4625a166a4a2a%7C0%7C0%7C637592695286846809%7CUnknown%7CTWFpbGZ
> > +sb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%
> > +3D%7C1000&amp;sdata=5qQ1PljM3e4Bn4%2FjdldYUHRBQL3jArJgRIAdLnhJraw%3D&
> > +amp;reserved=0
> > +
> > +title: Renesas RZ/G2L DMA Controller
> > +
> > +maintainers:
> > +  - Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> > +
> > +allOf:
> > +  - $ref: "dma-controller.yaml#"
> > +
> > +properties:
> > +  compatible:
> > +    items:
> > +      - enum:
> > +          - renesas,dmac-r9a07g044  # RZ/G2{L,LC}
> 
> Please use "renesas,r9a07g044-dmac".

OK. Will change.

> > +      - const: renesas,rz-dmac
> 
> Does this need many changes for RZ/A1H and RZ/A2M?

It will work on both RZ/A1H and RZ/A2M. I have n't tested since I don't have the board.
There is some difference in MID bit size. Other wise both identical.

 
> > +  renesas,rz-dmac-slavecfg:
> > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> > +    description: |
> > +      DMA configuration for a slave channel. Each channel must have an
> array of
> > +      3 items as below.
> > +      first item in the array is MID+RID
> 
> Already in dmas.
> 
> > +      second item in the array is slave src or dst address
> 
> As pointed out by Rob, already known by the slave driver.
> 
> > +      third item in the array is channel configuration value.
> 
> What exactly is this?
> Does the R-Car DMAC have this too? If yes, how does its driver handle it?

On R-CAR DMAC, we have only MID + RID values. Where as here we have channel configuration value With different set of parameter as mentioned in Table 16.4.

Please see Page 569, Table 16.4 On-Chip Module requests section. 

For eg:- as per Rob's suggestion, I have modelled the driver with the below entries in ALSA driver for playback/record use case.

dmas = <&dmac 0x255 0x10049c18 CH_CFG(0x1,0x0,0x1,0x0,0x2,0x1,0x1,0x0)>,
       <&dmac 0x256 0x10049c1c CH_CFG(0x0,0x0,0x1,0x0,0x2,0x1,0x1,0x0)>;
dma-names = "tx", "rx";

Using first parameter, it gets dmac channel. using second and third parameter it configures 
the channel.

Regards,
Biju

> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-
> 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




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