[PATCH 0/5] sunxi: enable automatic eMMC boot partition support

[Tom Rini]

On Tue, Nov 10, 2020 at 12:57:09PM +0000, André Przywara wrote:
> On 10/11/2020 12:38, Tom Rini wrote:
> 
> Hi Tom,
> 
> > On Sun, Nov 08, 2020 at 03:48:23PM +0000, André Przywara wrote:
> >> On 08/11/2020 14:59, Peter Robinson wrote:
> >>
> >> Hi,
> >>
> >>> On Sun, Nov 8, 2020 at 1:14 PM Andre Przywara <andre.przywara at arm.com> wrote:
> >>>>
> >>>> The eMMC standard describes the concept of boot partitions, consisting
> >>>> of two storage areas separate from the main user data partition.
> >>>> The Allwinner BootROM supports loading SPL/Boot0 from such a boot
> >>>> partition, if that is configured in the eMMC device [1].
> >>>>
> >>>> To load U-Boot proper along with the SPL from there, currently this
> >>>> requires to enable CONFIG_SUPPORT_EMMC_BOOT, and this means that this
> >>>> build won't boot from the normal eMMC user partition anymore.
> >>>> Also the raw MMC sector offset needs to be adjusted manually, preventing
> >>>> a boot from an SD card.
> >>>>
> >>>> This series introduces automatic detection of eMMC boot partition boot.
> >>>> Patch 3/5 automates the raw MMC sector offset decision, allowing such
> >>>> a build to also boot from an SD card.
> >>>> Unfortunately the BootROM does not mark an eMMC boot partition boot
> >>>> differently from the normal eMMC user data partition boot, so patch 4/5
> >>>> introduces a function that repeats the BootROM algorithm, so that the SPL
> >>>> comes to the same conclusion as the BootROM. This allows to build one
> >>>> single image that boots from everywhere: eMMC user data, eMMC boot,
> >>>> SD card, SPI flash.
> >>>> Patch 1/5 contains a bugfix that's needed in a later patch, patch 2/5
> >>>> extends the generic spl_mmc_boot_mode() interface to make 4/5 feasible.
> >>>>
> >>>> Without enabling CONFIG_SUPPORT_EMMC_BOOT, the AArch64 SPL grows by
> >>>> 92 bytes, ARMv7 grows by 36 bytes. With enabling the feature, the size
> >>>> goes up by 444 bytes (AArch64) and 260 bytes (ARMv7).
> >>>> Even for AArch64 this is still 4.5 KB below the SPL limit, so patch 5/5
> >>>> enables this new mechanism for some boards I could test this on.
> >>>>
> >>>> Please have a look and test this if you have a board with eMMC.
> >>>> I put installation instructions into the linux-sunxi Wiki:
> >>>> http://linux-sunxi.org/Bootable_eMMC
> >>>
> >>> It would probably be good to put that link in the local Allwinner docs
> >>> so it's easier for people to find.
> >>
> >> Yeah, actually as you mention it:
> >> There does not seem to be some generic README.sunxi file where this
> >> would belong to.
> >>
> >> Jagan: would it make sense to create one, and describe how to get U-Boot
> >> into the devices (SD card, eMMC, SPI flash, FEL)? That could move some
> >> parts of README.sunxi64 out of there, since they apply to all Allwinner
> >> devices.
> >>
> >> If people agree that this is the right thing to do, I would be happy to
> >> send a patch.
> > 
> > Well, rST file in doc/boards/ and all of that, but, yes please.
> 
> Ah, thanks for the pointer, looks good.
> Do we accept symlinks in the tree? There are quite some references to
> board/sunxi/README.sunxi64 out there. Or shall I keep a stub instead?

As there's external references to the README file, yes, please stub it
out pointing people to the new rST file.  Thanks!

-- 
Tom
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