Changing eMMC boot partition size

[Tom Rini]

On Tue, Nov 08, 2022 at 06:34:18PM +0100, Philip Oberfichtner wrote:
> Hi everybody,
> 
> I have a question regarding changing the eMMC boot partition size.
> According the the JEDEC eMMC spec it is read-only (BOOT_SIZE_MULT
> register).
> 
> But we still have mmc_boot_partition_size_change() in
> drivers/mmc/mmc_boot.c. It contains the comment
> 
> /* Only use this command for raw EMMC moviNAND. Enter backdoor mode */
> 
> What is moviNAND? My research pointed me to Samsung products only. So
> is changing the boot partition size vendor specific or can it be used
> more generally?
> 
> To be specific, I use the Kioxia THGBMJG6C1LBAB7 eMMC chip.

Yes, moviNAND was some Samsung technology that may or may not still be
used on some platforms. And yes, some eMMC parts do allow for boot
partitions to be resized but such information is often under NDA, so
contacting the hardware vendor or looking for eMMC chip documentation
may be helpful here.

-- 
Tom
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