Re: [PATCH 2/3] ARM: ixp4xx: Relax endianness

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Removing `depends on CPU_BIG_ENDIAN` breaks the IXP4XX flash driver on little-endian builds due to missing MTD CFI byte swapping logic.
--

--- Patch [2]: [PATCH 2/3] ARM: ixp4xx: Relax endianness ---
commit b77eacff0c25c139068c8fb9c88772bc9af87ae3
Author: Linus Walleij <linusw@kernel.org>

ARM: ixp4xx: Relax endianness

The IXP4xx can now boot in little endian mode so relax the endianness
requirements. This will make IXP4xx compile to little endian by default
like everyone else.

> diff --git a/arch/arm/mach-ixp4xx/Kconfig b/arch/arm/mach-ixp4xx/Kconfig
> index cb46802f5ce52..2bc8a497d3180 100644
> --- a/arch/arm/mach-ixp4xx/Kconfig
> +++ b/arch/arm/mach-ixp4xx/Kconfig
> @@ -2,7 +2,6 @@
>  menuconfig ARCH_IXP4XX
>  	bool "IXP4xx-based platforms"
>  	depends on ARCH_MULTI_V5
> -	depends on CPU_BIG_ENDIAN

[Severity: High]
Does removing this big-endian restriction break the IXP4XX flash driver on
little-endian builds?

The physmap-ixp4xx.c driver documents a hard requirement for the byte swap
option on LE systems:

drivers/mtd/maps/physmap-ixp4xx.c:flash_read16()
 * This means that on LE systems each 16 bit word must be swapped. Note that
 * this requires CONFIG_MTD_CFI_BE_BYTE_SWAP to be enabled to 'unswap' the CFI
 * data and other flash commands which are always in D7-D0.

However, the MTD_PHYSMAP_IXP4XX configuration conditionally selects the swap
only for big-endian builds:

drivers/mtd/maps/Kconfig:MTD_PHYSMAP_IXP4XX
	select MTD_CFI_BE_BYTE_SWAP if CPU_BIG_ENDIAN

Because of this conditional, LE builds fail to select the requisite byte swap.
Without the byte swap, the CFI backend defaults to host endian and the driver
sends mangled commands to the flash, causing it to fail to probe.

>  	select ARM_APPENDED_DTB # Old Redboot bootloaders deployed
>  	select CPU_XSCALE
>  	select GPIO_IXP4XX

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260709-ixp4xx-little-endian-v1-0-e9622d0ba9e4@kernel.org?part=2