[U-Boot] [EXT] [PATCH] arm64: mvebu: armada-8k: support SD card environment

[Kostya Porotchkin]

Hi, Baruch,

> -----Original Message-----
> From: Baruch Siach [mailto:baruch at tkos.co.il]
> Sent: Tuesday, December 19, 2017 08:43
> To: Kostya Porotchkin
> Cc: Stefan Roese; u-boot at lists.denx.de; Sergey Matyukevich
> Subject: Re: [EXT] [PATCH] arm64: mvebu: armada-8k: support SD card
> environment
> 
> Hi Kostya,
> 
> Thanks for reviewing.
> 
> On Thu, Dec 14, 2017 at 11:28:18AM +0000, Kostya Porotchkin wrote:
> > > Allow storing the environment on the Macchiatobin SD card. This is
> > > useful for distribution of SD card software images. Currently, the
> > > environment is always loaded from the SPI flash whose content might
> > > be incompatible with SD card kernel loading.
> > >
> > > Use the last 64KB of the 32MB boot partition as per the instructions
> > > in the Macchiatobin wiki:
> > >
> > >   http://wiki.macchiatobin.net/tiki-
> > > index.php?page=Setup+alternative+boot+sources
> > >
> > > Cc: Konstantin Porotchkin <kostap at marvell.com>
> > > Signed-off-by: Baruch Siach <baruch at tkos.co.il>
> > > ---
> > >  include/configs/mvebu_armada-8k.h | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > >
> > > diff --git a/include/configs/mvebu_armada-8k.h
> > > b/include/configs/mvebu_armada-8k.h
> > > index d85527434a0a..0457a72e353b 100644
> > > --- a/include/configs/mvebu_armada-8k.h
> > > +++ b/include/configs/mvebu_armada-8k.h
> > > @@ -73,7 +73,12 @@
> > >  #define CONFIG_SF_DEFAULT_MODE		SPI_MODE_0
> > >  #define CONFIG_ENV_SPI_MODE		CONFIG_SF_DEFAULT_MODE
> > >
> > > +#if defined(CONFIG_ENV_IS_IN_SPI_FLASH)
> > >  #define CONFIG_ENV_OFFSET		0x180000 /* as Marvell U-Boot
> version */
> > > +#elif defined(CONFIG_ENV_IS_IN_MMC)
> > > +#define CONFIG_SYS_MMC_ENV_DEV		1
> > > +#define CONFIG_ENV_OFFSET		0x21f0000
> > > +#endif
> >
> > I think this will break boot from the on-board eMMC device.
> > Maybe the environment offset should be connected to the MMC device ID.
> > So it will be different for SD and eMMC.
> > The eMMC boot partition is not that big as the space on SD allocated
> for the boot images.
> > Additionally, the SD pre-allocated boot space is not really a constant
> value.
> 
> So what would you suggest? How can we detect the location of the SD/eMMC
> stored environment? Would a per-board 'u-boot,mmc-env-offset' DT
> property help? Maybe move to CONFIG_ENV_IS_IN_FAT?
[Konstantin Porotchkin] 
What we know for sure is that partition 0 is always the data partition for both SD and eMMC.
This is the only partition in case of SD and it less likely to be used with eMMC at all.
So we can, for example, use your environment offset when the CONFIG_SYS_MMC_ENV_PART=0
As for the value of CONFIG_SYS_MMC_ENV_DEV, we cannot assume that it will have the same meaning for all Marvell A8K platforms. On some boards the device 1 may be the eMMC as well.
Since this header is shared across all boards, I would not hard code the device 1 as SD.
Using file for the environment storage when we boot from the data partition is also possible.
In this case we do not have the dependency from the size of the empty space allocated before the first partition entry.

Kosta
> 
> baruch
> 
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