linux-kernel - Re: [PATCH v3 5/13] mmc: sunxi: Mask DATA0 when updating the clock

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Message-ID: <20170125091613.hmlqoeh6hlqh57wh@lukather>
Date:   Wed, 25 Jan 2017 10:16:13 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Andre Przywara <andre.przywara@....com>
Subject: Re: [PATCH v3 5/13] mmc: sunxi: Mask DATA0 when updating the clock

On Tue, Jan 24, 2017 at 09:18:46AM +0100, Ulf Hansson wrote:
> On 16 January 2017 at 17:56, Maxime Ripard
> <maxime.ripard@...e-electrons.com> wrote:
> > The A64 MMC controllers need DATA0 to be masked while updating the clock,
> > otherwise any subsequent command will result in a timeout.
> 
> Could you elaborate on what mask DATA0 really means? I don't follow.

To be honest, I don't really know :)

This is how it's called both in the vendor tree and the datasheet. I
*think* it might be the first data line on the bus, but I'm not sure
exactly why that would cause any issue when updating the clock.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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