[U-Boot] [PATCH 3/4] mmc: exynos dwmmc: check boot mode before init dwmmc

From: Tom Rini <trini@ti.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH 3/4] mmc: exynos dwmmc: check boot mode before init dwmmc
Date: Thu, 19 Feb 2015 09:01:42 -0500	[thread overview]
Message-ID: <20150219140142.GH25879@bill-the-cat> (raw)
In-Reply-To: <CAPnjgZ1iN5JA=dG-SdUF7sumxE-SaezZNw-c4yKrwBmkE+Hgyg@mail.gmail.com>

On Tue, Feb 17, 2015 at 10:02:03PM -0700, Simon Glass wrote:
> Hi Przemyslaw,
> 
> On 17 February 2015 at 06:09, Przemyslaw Marczak <p.marczak@samsung.com> wrote:
> > Before this commit, the mmc devices were always registered
> > in the same order. So dwmmc channel 0 was registered as mmc 0,
> > channel 1 as mmc 1, etc.
> > In case of possibility to boot from more then one device,
> > the CONFIG_SYS_MMC_ENV_DEV should always point to right mmc device.
> >
> > This can be achieved by init boot device as first, so it will be
> > always registered as mmc 0. Thanks to this, the 'saveenv' command
> > will work fine for all mmc boot devices.
> >
> > Exynos based boards usually uses mmc host channels configuration:
> > - 0, or 0+1 for 8 bit  - as a default boot device (usually eMMC)
> > - 2 for 4bit - as an optional boot device (usually SD card slot)
> >
> > And usually the boot order is defined by OM pin configuration,
> > which can be changed in a few ways, eg.
> > - Odroid U3     - eMMC card insertion -> first boot from eMMC
> > - Odroid X2/XU3 - boot priority jumper
> >
> > By this commit, Exynos dwmmc driver will check the OM pin configuration,
> > and then try to init the boot device and register it as mmc 0.
> 
> I think a better way to do this would be to make
> CONFIG_SYS_MMC_ENV_DEV support an option where the device can be
> selected at run-time.
> 
> However that would probably be better done when the drive rmodel
> conversion is complete.

Yes, lets hold off on this until driver model is in and we can do this
more cleanly rather than whack at this problem right now (I've seen
solutions to this kind of problem on am335x for example and it's still
going to be better to wait I think).

-- 
Tom
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