Re: [PATCH 1/2] dt-bindings: mmc: mtk-sd: add single burst switch

[Conor Dooley <conor@kernel.org>]

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On Fri, Mar 07, 2025 at 06:59:03AM +0000, Axe Yang (杨磊) wrote:
> On Thu, 2025-03-06 at 10:19 +0100, AngeloGioacchino Del Regno wrote:
> > External email : Please do not click links or open attachments until
> > you have verified the sender or the content.
> > 
> > 
> > Il 06/03/25 09:48, Axe Yang ha scritto:
> > > Add 'mediatek,disable-single-burst' setting. This property can be
> > > used to switch bus burst type, from single burst to INCR, which is
> > > determined by the bus type within the IP. Some versions of the IP
> > > are using AXI bus, thus this switch is necessary as 'single' is not
> > > the burst type supported by the bus.
> > > 
> > > Signed-off-by: Axe Yang <axe.yang@mediatek.com>
> > 
> > I am mostly sure that this is not something to put in devicetree, but
> > as
> > platform data for specific SoC(s), as much as I'm mostly sure that
> > all of
> > the instances of the MSDC IP in one SoC will be *all* using either
> > single
> > or INCR.
> 
> No, actually MSDC IPs in one SoC are using different versions.
> Usually MSDC1 (index from 1) is used as eMMC host, the left hosts are
> used as SD/SDIO hosts. They have similar designs, but there are still
> difference.
> 
> > 
> > So, I think I know the answer but I'll still ask just to be extremely
> > sure:
> > 
> > is there any MediaTek SoC that has different IP versions for
> > different MSDC
> > instances, and that hence require single burst on one instance and
> > INCR on
> > another instance?
> 
> Yes. Actually every SoC has different IP versions for eMMC and SD/SDIO
> host as I said.
> e.g. For MT8168, signel burst bit should be set to 1 for eMMC Host, but
> 0 for SD/SDIO Host.
> 

Sounds like two different IPs that really should have different
compatibles to me...

> > 
> > And if there is - is there a pattern? Is it always SDIO requiring
> > INCR or
> > always eMMC/SD requiring it?
> > 
> > 
> 
> No, there is no pattern. Both eMMC and SD/SDIO hosts need to be
> configured base on IP version. There is no binding relationship between
> eMMC/SD/SDIO and the burst type. eMMC burst type might be INCR or
> single, same as SD/SDIO.
> 
> 
> Regards,
> Axe
> 
> 
> > 
> > > ---
> > >   Documentation/devicetree/bindings/mmc/mtk-sd.yaml | 8 ++++++++
> > >   1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
> > > b/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
> > > index 0debccbd6519..6076aff0a689 100644
> > > --- a/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
> > > +++ b/Documentation/devicetree/bindings/mmc/mtk-sd.yaml
> > > @@ -100,6 +100,14 @@ properties:
> > >       minimum: 0
> > >       maximum: 0xffffffff
> > > 
> > > +  mediatek,disable-single-burst:
> > > +    $ref: /schemas/types.yaml#/definitions/flag
> > > +    description:
> > > +      Burst type setting. For some versions of the IP that do not
> > > use
> > > +      AHB bus, the burst type need to be switched to INCR.
> > > +      If present, use INCR burst type.
> > > +      If not present, use single burst type.
> > > +
> > >     mediatek,hs200-cmd-int-delay:
> > >       $ref: /schemas/types.yaml#/definitions/uint32
> > >       description:
> > 
> > 
> > 

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