From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wolfram Sang <wsa@the-dreams.de>
Subject: Re: [PATCH 1/3] dt-bindings: mmc: Add
 'fixed-emmc-driver-type-hs{200,400}'
Date: Tue, 5 Nov 2019 07:22:23 +0100
Message-ID: <20191105062223.GB1048@kunai>
References: <20191105055015.23656-1-erosca@de.adit-jv.com>
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To: Eugeniu Rosca <erosca@de.adit-jv.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>, Adrian Hunter <adrian.hunter@intel.com>, Wolfram Sang <wsa+renesas@sang-engineering.com>, linux-mmc@vger.kernel.org, Linus Walleij <linus.walleij@linaro.org>, Mathieu Malaterre <malat@debian.org>, Pavel Machek <pavel@ucw.cz>, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Eugeniu Rosca <roscaeugeniu@gmail.com>
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Hi Eugeniu,

thanks for this work!

> A certain eMMC manufacturer provided below requirement:
>  ---snip---
>  Use "drive strength" value of 4 or 1 for HS400 or 0 for HS200.
>  ---snip---

I see.

> The existing "fixed-emmc-driver-type" property [1] is the closest one
> to implement the above, but it falls short due to being unable to define
> two values to differentiate between HS200 and HS400 (both modes may be
> supported by the same non-removable MMC device).
>=20
> To allow users to set a preferred HS200/HS400 "drive strength", provide
> two more bindings inspired from [1]:
>  - fixed-emmc-driver-type-hs200
>  - fixed-emmc-driver-type-hs400

Main question before looking at the code: Can't we just extend the
existing binding with an optional second parameter?

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I tend to favour this approach...

> For more details about eMMC I/O driver strength types, see Jedec spec.
> Keep "fixed-emmc-driver-type" in place for backward compatibility.

If we decide for the path proposed here, should the old binding be
deprecated then?

Happy hacking,

   Wolfram


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