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

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Message-ID: <f84800fac589429157cd84034ef2f4541d3486a7.camel@mediatek.com>
Date: Fri, 7 Mar 2025 06:59:03 +0000
From: Axe Yang (杨磊) <Axe.Yang@...iatek.com>
To: Wenbin Mei (梅文彬) <Wenbin.Mei@...iatek.com>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>,
	Chaotian Jing (井朝天)
	<Chaotian.Jing@...iatek.com>, "robh@...nel.org" <robh@...nel.org>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>, "ulf.hansson@...aro.org"
	<ulf.hansson@...aro.org>, "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Andy-ld Lu (卢东) <Andy-ld.Lu@...iatek.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Yong Mao (毛勇) <yong.mao@...iatek.com>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>,
	Qingliang Li (黎晴亮) <Qingliang.Li@...iatek.com>
Subject: Re: [PATCH 1/2] dt-bindings: mmc: mtk-sd: add single burst switch

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@...iatek.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.

> 
> 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:
> 
> 
>