linux-kernel - Re: [PATCH 2/2] arm64: dts: meson: libretech-cc: switch eMMC to 1.8v

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Date:   Thu, 10 Jan 2019 16:53:35 -0800
From:   Kevin Hilman <khilman@...libre.com>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Carlo Caione <carlo@...one.org>, devicetree@...r.kernel.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] arm64: dts: meson: libretech-cc: switch eMMC to 1.8v

Jerome Brunet <jbrunet@...libre.com> writes:

> On Sat, 2018-12-22 at 18:01 +0100, Martin Blumenstingl wrote:
>> Hi Jerome,
>> 
>> On Thu, Dec 20, 2018 at 5:11 PM Jerome Brunet <jbrunet@...libre.com> wrote:
>> > While some 3.3v eMMC 4.0 are available from libretech, the default
>> > option for the aml-s905x-cc seems to 1.8v 5.0 modules.
>> nit-pick:
>> can you please state which module (storage size) you used for testing?
>> you probably still remember that we had some confusion on Odroid-C2
>> which eMMC module works and which doesn't, so let's be explicit here
>> 
>> > Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
>> > ---
>> >  .../boot/dts/amlogic/meson-gxl-s905x-libretech-cc.dts    | 9 +++++----
>> >  1 file changed, 5 insertions(+), 4 deletions(-)
>> > 
>> > diff --git a/arch/arm64/boot/dts/amlogic/meson-gxl-s905x-libretech-cc.dts
>> > b/arch/arm64/boot/dts/amlogic/meson-gxl-s905x-libretech-cc.dts
>> > index daad007fac1f..d0d202cf7161 100644
>> > --- a/arch/arm64/boot/dts/amlogic/meson-gxl-s905x-libretech-cc.dts
>> > +++ b/arch/arm64/boot/dts/amlogic/meson-gxl-s905x-libretech-cc.dts
>> > @@ -118,8 +118,8 @@
>> >         vddio_boot: regulator-vddio_boot {
>> >                 compatible = "regulator-fixed";
>> >                 regulator-name = "VDDIO_BOOT";
>> > -               regulator-min-microvolt = <3300000>;
>> > -               regulator-max-microvolt = <3300000>;
>> > +               regulator-min-microvolt = <1800000>;
>> > +               regulator-max-microvolt = <1800000>;
>> is there a 3.3V -> 1.8V regulator on the eMMC module?
>> I'm not sure about the schematics but it seems to be that the board
>> itself supplies only 3.3V to the eMMC connector, so I'm not sure where
>> 1.8V come from in this case
>
> The module is indeed fed by 3.3v only but it has embedded LDOs add will feed
> back the supply of the BOOT gpio bank.
>
> I tried the following modules:
> * 8 GB samsung - v1.0-170420
> * 32 GB toshiba - v1.0-170421
>
> I think you can't get them here [0].
>
> In theory, these 4.x modules [1] could also work. They don't have the LDOs and
> are directly feeding back the 3.3v to the BOOT bank. Since the modules are
> advertised as being compatible with the Allwinner boards only, and not the AML
> ones, it should not be the default option.
>
> [0] : 
> https://www.loverpi.com/collections/libre-computer-project/products/libre-computer-board-emmc-5-x-module?variant=4173557729
> [1] : 
> https://www.loverpi.com/collections/libre-computer-project/products/libre-computer-board-emmc-4-x-module?variant=761282232333
>
>> can you please add a comment to the .dts about this?
>
> Sure
>

OK, I'll wait for a v2 of this series.

Kevin