linux-kernel - Re: [PATCH 1/2] dt-bindings: arm: sunxi: add OrangePi 3 with eMMC

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Message-ID: <20200117182537.scttsuq26g6v6yno@gilmour.lan>
Date:   Fri, 17 Jan 2020 19:25:37 +0100
From:   Maxime Ripard <mripard@...nel.org>
To:     Jernej Škrabec <jernej.skrabec@...l.net>
Cc:     Rob Herring <robh+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Mark Rutland <mark.rutland@....com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] dt-bindings: arm: sunxi: add OrangePi 3 with eMMC

Hi,

On Thu, Jan 16, 2020 at 05:33:45PM +0100, Jernej Škrabec wrote:
> Dne četrtek, 16. januar 2020 ob 13:29:44 CET je Maxime Ripard napisal(a):
> > On Thu, Jan 16, 2020 at 12:10:58AM +0100, Jernej Škrabec wrote:
> > > Hi!
> > >
> > > Dne sreda, 15. januar 2020 ob 22:57:31 CET je Rob Herring napisal(a):
> > > > On Wed, Jan 15, 2020 at 1:42 PM Jernej Skrabec <jernej.skrabec@...l.net>
> > >
> > > wrote:
> > > > > OrangePi 3 can optionally have eMMC. Add a compatible for it.
> > > >
> > > > Is this just a population option or a different board layout? If the
> > > > former, I don't think you need a new compatible, just add/enable a
> > > > node for the eMMC.
> > >
> > > I have only board with eMMC but I imagine it's the former. Even so,
> > > current
> > > approach with Allwinner boards is to have two different board DT files,
> > > one for each variant. This can be seen from
> > > Documentation/devicetree/bindings/arm/ sunxi.yaml which has a lot of
> > > compatibles ending with "-emmc". I guess reason for that is to avoid
> > > having MMC controller being powered on for no reason.
> > The main reason for that is that those populating options can be
> > conflicting. For example, last week we discussed an issue about the
> > eMMC being on the same pin set than an SPI flash, both options being
> > available.
> >
> > The solution Andre suggested then was to let the eMMC be disabled, and
> > have the bootloader probe the emmc, and if found, enable
> > it. Otherwise, it means that you have a SPI flash (and enable it).
> >
> > I guess a similar solution would apply here.
>
> From what I can tell from schematic, pins are dedicated for eMMC.
>
> So what solution do you suggest? Put eMMC node in original OrangePi 3 DT and
> set status to disabled?

If it's always dedicated to eMMC, but the eMMC is not always there, I
guess we could remove the non-removable property from the eMMC
mode. IIRC, without it (and without CD GPIO), it will fall-back to
polling the card and will be able to detect it if it's there (and not
use it if it's not).

Maxime

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