[REGRESSION] [PATCH 1/1] mtd: mtdpart: Support MTD_SIZE_REMAINING with unallocated memory area

[Weijie Gao (高惟杰)]

On Tue, 2025-04-22 at 15:07 +0200, Francesco Dolcini wrote:
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> 
> On Tue, Apr 22, 2025 at 03:05:58PM +0200, Alexander Stein wrote:
> > Am Dienstag, 22. April 2025, 12:37:32 CEST schrieb Francesco
> > Dolcini:
> > > On Thu, Feb 20, 2025 at 03:58:07PM +0100, Alexander Stein wrote:
> > > > If there is an unallocated memory area before the last, filling
> > > > parting
> > > > the size calculation for MTD_SIZE_REMAINING does not take this
> > > > hole
> > > > into account.
> > > > Fix this by calculating the remaining size just based on total
> > > > size
> > > > and partition offset.
> > > > 
> > > > Signed-off-by: Alexander Stein <alexander.stein at ew.tq-group.com
> > > > >
> > > 
> > > This change introduced a regression on colibri imx7 and imx6ull.
> > > 
> > > ```
> > > Booting from NAND...
> > > Partition size must be a multiple of 2048
> > > Could not parse device nand0
> > > Failed parsing MTD partitions from mtdparts!
> > > Partition ubi not found!
> > > ```
> > > 
> > > Reverting commit 1ca97ee90392 ("mtd: mtdpart: Support
> > > MTD_SIZE_REMAINING
> > > with unallocated memory area") on top of current master fixes the
> > > issue.
> > > 
> > > Any suggestion? I have not looked at the code, I just did a git
> > > bisect.
> > 
> > How does your mtdparts look like?
> 
> $ grep mtdparts configs/colibri_imx7_defconfig
> CONFIG_MTDPARTS_DEFAULT="mtdparts=gpmi-nand:512k(mx7-bcb),1536k(u-
> boot1)ro,1536k(u-boot2)ro,512k(u-boot-env),-(ubi)"
> 

I just reproduced this issue with a rather simple mtdparts:
mtdparts=2048k(bl2),-(ubi)

After printing some log, I beliebve this is caused by the mtd partition
offset value:
```
spi-nand: spi_nand spi_nand at 0: 128 MiB, block size: 128 KiB, page size:
2048, OOB size: 64
parent->writesize = 0x800
parent->size = 0x8000000
parts[0]: name = bl2, offset = 0xffffffffffffffff, size = 0x200000
parts[1]: name = ubi, offset = 0xffffffffffffffff, size = 0x8000001
Partition size must be a multiple of 2048
Could not parse device spi-nand0
Failed parsing MTD partitions from mtdparts!
Partition ubi not found!
```

The mtd partition offset has not been updated when calculating the mtd
partition size:
```
		if (parts[idx].size == MTD_SIZE_REMAINING)
			parts[idx].size = parent->size -
parts[idx].offset;
```

It's also easy to solve: calculate the offset before calculating the
size