From: Ulf Hansson <ulf.hansson@linaro.org>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Richard Leitner <richard.leitner@skidata.com>,
Bart Van Assche <bart.vanassche@sandisk.com>,
Luca Porzio <lporzio@micron.com>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Shawn Lin <shawn.lin@rock-chips.com>,
Adrian Hunter <adrian.hunter@intel.com>,
Jaehoon Chung <jh80.chung@samsung.com>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Richard Leitner <dev@g0hl1n.net>
Subject: Re: [PATCH v2] mmc: core: add mmc-card hardware reset enable support
Date: Tue, 11 Apr 2017 12:43:39 +0200 [thread overview]
Message-ID: <CAPDyKFoL5dbs_xKxaBGk2bqd2tOXrhG_SVcBoUpMetsKDdNXxQ@mail.gmail.com> (raw)
In-Reply-To: <CACRpkdaBrk91hh3JGZ0vcD3aXO+OHD41xwRKn9prPSOX_SXuWg@mail.gmail.com>
On 11 April 2017 at 10:17, Linus Walleij <linus.walleij@linaro.org> wrote:
> On Tue, Apr 11, 2017 at 9:31 AM, Richard Leitner
> <richard.leitner@skidata.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@skidata.com>
>
> Do we know *WHY* these cards disable their hardware reset lines?
Allow me to make a guess. In case the reset isn't enabled, the
internal eMMC card firmware don't monitor the pin for the reset. I
guess that could makes sense if SoC vendors has failed to properly
connect the pin, avoiding the eMMC card to be reset when it shouldn't.
>
> 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.
There is actually already a DT property "cap-mmc-hw-reset"
(MMC_CAP_HW_RESET), which tells whether the eMMC reset is supported by
the host.
Perhaps we can consider to force-enabling it for the eMMC card, when
this property is set for the mmc host!? At least, inventing yet
another binding doesn't make sense to me.
>
> Putting some people who work for eMMC vendors in the To: line so they
> can say if they know about this.
Yes, let's see what they say about it.
>
> Yours,
> Linus Walleij
Kind regards
Uffe
next prev parent reply other threads:[~2017-04-11 10:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-11 7:31 [PATCH v2] mmc: core: add mmc-card hardware reset enable support Richard Leitner
2017-04-11 8:17 ` Linus Walleij
2017-04-11 10:43 ` Ulf Hansson [this message]
2017-06-14 7:25 ` Richard Leitner
2017-06-14 16:12 ` [EXT] " Luca Porzio (lporzio)
2017-06-20 9:45 ` Linus Walleij
2017-06-20 10:24 ` Richard Leitner
2017-06-20 16:10 ` Linus Walleij
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