From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ulf Hansson <ulf.hansson@linaro.org>
Subject: Re: [PATCH v2] mmc: sdhci: wait 5ms after set 1.8V signal enable
Date: Thu, 14 Dec 2017 09:41:11 +0100
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References: <1513208929-13578-1-git-send-email-zjwu@marvell.com>
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To: Zhoujie Wu <zjwu@marvell.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>, "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>, Nadav Haklai <nadavh@marvell.com>, Victor Gu <xigu@marvell.com>, xswang@marvell.com, Wilson Ding <dingwei@marvell.com>, Kostya Porotchkin <kostap@marvell.com>, Hanna Hawa <hannah@marvell.com>, hongd@marvell.com, Doug Jones <dougj@marvell.com>, Ryan Gao <ygao@marvell.com>, "Wei(SOCP) Liu" <liuw@marvell.com>, Gregory Clement <gregory.clement@free-electrons.com>, Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

On 14 December 2017 at 00:48, Zhoujie Wu <zjwu@marvell.com> wrote:
> According to SD spec 3.00 3.6.1 signal voltage switch
> procedure, host should wait 5ms after set 1.8V signal
> enable bit in Host Control 2 register and check if 1.8V
> is stable or not.
>

The core already deals with this. See mmc_set_uhs_voltage() and
mmc_host_set_uhs_voltage().

We even have a retry mechanism in place.

> On some cards, found without the delay would see "1.8V
> regulator output did not became stable" err log.

Seems like you need to fix the regulator instead.

BTW, is this a regression? No?

[...]

Kind regards
Uffe