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From:   Giulio Benetti <giulio.benetti@benettiengineering.com>
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Subject: Re: [PATCH v2 11/13] mmc: sdhci-esdhc-imx: Add sdhc support for i.MXRT series
Date:   Thu, 4 Nov 2021 03:30:33 +0100
Message-Id: <B67A91BD-DAE9-468B-8731-251DE86E6B5B@benettiengineering.com>
References: <YYMx28VvhR7nvMlt@robh.at.kernel.org>
Cc:     Jesse Taube <mr.bossman075@gmail.com>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Sascha Hauer <kernel@pengutronix.de>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Dong Aisheng <aisheng.dong@nxp.com>,
        Stefan Agner <stefan@agner.ch>,
        Linus Walleij <linus.walleij@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Arnd Bergmann <arnd@arndb.de>, Olof Johansson <olof@lixom.net>,
        soc@kernel.org, Russell King - ARM Linux <linux@armlinux.org.uk>,
        Abel Vesa <abel.vesa@nxp.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Jiri Slaby <jirislaby@kernel.org>,
        Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>,
        linux-clk <linux-clk@vger.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-mmc <linux-mmc@vger.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
        linux-serial@vger.kernel.org
In-Reply-To: <YYMx28VvhR7nvMlt@robh.at.kernel.org>
To:     Rob Herring <robh@kernel.org>
Precedence: bulk

Hello Rob, Jesse, All,

> Il giorno 4 nov 2021, alle ore 02:05, Rob Herring <robh@kernel.org> ha scr=
itto:
>=20
> =EF=BB=BFOn Wed, Nov 03, 2021 at 12:30:17AM +0100, Giulio Benetti wrote:
>> Hi Fabio, Jesse, All,
>>=20
>>> On 11/3/21 12:25 AM, Jesse Taube wrote:
>>>=20
>>>=20
>>> On 11/2/21 19:17, Fabio Estevam wrote:
>>>> On Tue, Nov 2, 2021 at 7:57 PM Jesse Taube <mr.bossman075@gmail.com> wr=
ote:
>>>>=20
>>>>>   static struct esdhc_soc_data usdhc_imx8qxp_data =3D {
>>>>>          .flags =3D ESDHC_FLAG_USDHC | ESDHC_FLAG_STD_TUNING
>>>>> @@ -357,6 +363,7 @@ static const struct of_device_id imx_esdhc_dt_ids[=
] =3D {
>>>>>          { .compatible =3D "fsl,imx7ulp-usdhc", .data =3D &usdhc_imx7u=
lp_data, },
>>>>>          { .compatible =3D "fsl,imx8qxp-usdhc", .data =3D &usdhc_imx8q=
xp_data, },
>>>>>          { .compatible =3D "fsl,imx8mm-usdhc", .data =3D &usdhc_imx8mm=
_data, },
>>>>> +       { .compatible =3D "fsl,imxrt-usdhc", .data =3D &usdhc_imxrt_da=
ta, },
>>>>=20
>>>> I thought Rob suggested to use the SoC name, so this would be:
>>>>=20
>>> Uh i think that may have been for the UART.
>>>> { .compatible =3D "fsl,imxrt1050-usdhc", .data =3D &usdhc_imxrt1050_dat=
a, },
>>>>=20
>>>> The same applies to the other bindings in the series.
>>>>=20
>>>> This way it would be possible to differentiate between future
>>>> supported i.MX RT devices.
>>>>=20
>>> This makes sense will do in V3.
>>>=20
>>=20
>> If we add every SoC we will end up having a long list for every device
>> driver. At the moment it would be 7 parts:
>> 1) imxrt1020
>> 2) imxrt1024
>> .
>> .
>> .
>> 7) imxrt1170
>=20
> You don't need a driver update if you use a fallback. When you add=20
> the 2nd chip, if you think it is 'the same', then you do:
>=20
> compatible =3D "fsl,imxrt1024-usdhc", "fsl,imxrt1050-usdhc";
>=20
> That requires no driver update until the driver needs to handle some=20
> difference. And when there is a difference, you don't need a DT update.

This solution is pretty fine, we=E2=80=99re going with that then, for this a=
nd every driver involved.

Thank you for pointing us.

Best regards
Giulio Benetti
Benetti Engineering sas

>=20
> You could make "fsl,imxrt-usdhc" the fallback from the start if you are=20=

> adverse to the first way.
>=20
> Rob