linux-kernel - Re: [PATCH v2] mmc: core: add mmc-card hardware reset enable support

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Message-ID: <CACRpkdaBrk91hh3JGZ0vcD3aXO+OHD41xwRKn9prPSOX_SXuWg@mail.gmail.com>
Date:   Tue, 11 Apr 2017 10:17:58 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Richard Leitner <richard.leitner@...data.com>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        Luca Porzio <lporzio@...ron.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Richard Leitner <dev@...l1n.net>
Subject: Re: [PATCH v2] mmc: core: add mmc-card hardware reset enable support

On Tue, Apr 11, 2017 at 9:31 AM, Richard Leitner
<richard.leitner@...data.com> wrote:

> Some eMMCs disable their hardware reset line (RST_N) by default. To enable
> it the host must set the corresponding bit in ECSD. An example for such
> a device is the Micron MTFCxGACAANA-4M.
>
> This patch adds a new mmc-card devicetree property to let the host enable
> this feature during card initialization.
>
> Signed-off-by: Richard Leitner <richard.leitner@...data.com>

Do we know *WHY* these cards disable their hardware reset lines?

If it is just some random over-cautious panic thing we might consider
just force re-enableing it, maybe with a warning in the dmesg, so we can
always reset the card. No DT property needed.

Putting some people who work for eMMC vendors in the To: line so they
can say if they know about this.

Yours,
Linus Walleij