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From:   Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
To:     Rob Herring <robh@kernel.org>
CC:     "joel@jms.id.au" <joel@jms.id.au>,
        "mturquette@baylibre.com" <mturquette@baylibre.com>,
        "sboyd@kernel.org" <sboyd@kernel.org>,
        "adrian.hunter@intel.com" <adrian.hunter@intel.com>,
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        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-clk@vger.kernel.org" <linux-clk@vger.kernel.org>,
        "andrew@aj.id.au" <andrew@aj.id.au>,
        BMC-SW <BMC-SW@aspeedtech.com>,
        Steven Lee <steven_lee@aspeedtech.com>
Subject: RE: [PATCH 10/10] dt-bindings: mmc: aspeed: Add a new compatible
 string
Thread-Topic: [PATCH 10/10] dt-bindings: mmc: aspeed: Add a new compatible
 string
Thread-Index: AQHXs9HHr7TBfuGZLUCpoIBAXdEJGKu4upXg
Date:   Tue, 28 Sep 2021 02:50:59 +0000
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References: <20210922103116.30652-1-chin-ting_kuo@aspeedtech.com>
 <20210922103116.30652-11-chin-ting_kuo@aspeedtech.com>
 <YVIUf7/4ukMcrOb9@robh.at.kernel.org>
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Hi Rob,

> -----Original Message-----
> From: Rob Herring <robh@kernel.org>
> Sent: Tuesday, September 28, 2021 2:59 AM
> To: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
> Subject: Re: [PATCH 10/10] dt-bindings: mmc: aspeed: Add a new compatible
> string
>=20
> On Wed, Sep 22, 2021 at 06:31:16PM +0800, Chin-Ting Kuo wrote:
> > Add "aspeed,ast2600-emmc" compatible string for the sake of
> > distinguishing between SD and eMMC device.
>=20
> Why?
>=20
> Is the h/w block different? We already have properties to handle some of =
the
> eMMC specifics. Also, you can have a child node for the eMMC device if yo=
u
> need that.

There are two SD/SDIO controllers in a AST2600 SoC.
One is for SD card and the other is for eMMC.
Although both of them are embedded in the same SoC, the design of delay cel=
l and
the manufacture process are different. The delay phase is definitely differ=
ent and, thus,
we need a flag, compatible, to distinguish the device, SD or eMMC.

Without "aspeed,ast2600-emmc" compatible, of course, eMMC device can work w=
ith original
sdhci driver and device tree setting. But, for ultra-speed or HS200 case, A=
ST2600 SoC needs some
phase delay which (maximum) value is different between SD and eMMC device.

>=20
> >
> > Signed-off-by: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
> > ---
> >  Documentation/devicetree/bindings/mmc/aspeed,sdhci.yaml | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/Documentation/devicetree/bindings/mmc/aspeed,sdhci.yaml
> > b/Documentation/devicetree/bindings/mmc/aspeed,sdhci.yaml
> > index 5bb66849df65..41105cd104c6 100644
> > --- a/Documentation/devicetree/bindings/mmc/aspeed,sdhci.yaml
> > +++ b/Documentation/devicetree/bindings/mmc/aspeed,sdhci.yaml
> > @@ -52,6 +52,7 @@ patternProperties:
> >            - aspeed,ast2400-sdhci
> >            - aspeed,ast2500-sdhci
> >            - aspeed,ast2600-sdhci
> > +          - aspeed,ast2600-emmc
> >        reg:
> >          maxItems: 1
> >          description: The SDHCI registers
> > --
> > 2.17.1
> >
> >