linux-kernel - Re: [PATCH v5 0/13] arm64: allwinner: a64: Enable MMC support

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Message-ID: <20170130104218.34zftrdyr3m6422w@lukather>
Date:   Mon, 30 Jan 2017 11:42:18 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Andre Przywara <andre.przywara@....com>
Subject: Re: [PATCH v5 0/13] arm64: allwinner: a64: Enable MMC support

Hi,

On Sat, Jan 28, 2017 at 08:44:02PM +0800, Chen-Yu Tsai wrote:
> On Sat, Jan 28, 2017 at 5:38 AM, Maxime Ripard
> <maxime.ripard@...e-electrons.com> wrote:
> > Hi,
> >
> > Here is a new attempt at getting the MMC controllers running, following the
> > work done by Andre.
> >
> > This has been tested on a board with one SDIO device (a Marvell WiFi chip)
> > and a Kingston eMMC with 1.8V IOs.
> >
> > For SDIO, the HS DDR mode works just fine. That serie also enables the
> > SDR104 mode to work on the devices that are capable of this.
> >
> > For the eMMC, HS200 with the voltage switch works. HS400 doesn't at the
> > moment, but since it's significantly more complex, and at the same time
> > Allwinner recommends to limit its frequency to 100MHz, this doesn't have
> > any benefits. If there's any at some point, this can be added later.
> 
> Whole series is
> 
> Acked-by: Chen-Yu Tsai <wens@...e.org>
> 
> Seems that we don't need to increase the signal drive strength for eMMC
> on the A64? This is probably a good thing.

From what I've seen, Allwinner still recommends using a 30mA drive
strength, so that doesn't seem needed.

Maxime

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

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