Re: [PATCH v6 01/11] mtd: core: always create master device

Guenter Roeck
2025-06-09T13:08:22Z

On 6/9/25 05:23, Usyskin, Alexander wrote:
>> Subject: Re: [PATCH v6 01/11] mtd: core: always create master device
>>
>>
>>>>>> Several of my qemu boot tests fail to boot from mtd devices with this
>> patch
>>>>>> in the mainline kernel. Reverting it fixes the problem. As far as I can
>>>>>> see this affects configurations with
>> CONFIG_MTD_PARTITIONED_MASTER=y
>>>>>> when
>>>>>> trying to boot from an mtd partition other than mtdblock0, with the
>>>>>> mtd partition data in devicetree (.../aspeed/openbmc-flash-layout.dtsi).
>>>>>> Is there a guidance describing the changed behavior, by any chance,
>>>>>> and how the boot command line now needs to look like when using one
>> of
>>>>>> the flash partitions as root file system ?
>>>>>>
>>>>>> Thanks,
>>>>>> Guenter
>>>>>
>>>>> I've tried to make is as transparent as possible for the existing users.
>>>>> Only change is that now every partition has master that is not partitioned.
>>>>> Is the CONFIG_MTD_PARTITIONED_MASTER=n fixed the problem for you?
>>>> No change is expected, can you please describe the devices that you
>>>> observe with and without the patch? Maybe there is something wrong in
>>>> the core logic.
>>>>
>>>
>>> I am trying to boot supermicro-x11spi-bmc in qemu from flash partition 6.
>>> The qemu command line is something like
>>>
>>> qemu-system-arm -M supermicro-x11spi-bmc,fmc-
>> model=n25q256a13,spi-model=n25q256a13 \
>>> -kernel arch/arm/boot/zImage -no-reboot -snapshot \
>>> -audio none \
>>> -drive file=/tmp/flash,format=raw,if=mtd,index=1 \
>>> -nic user \
>>> --append "root=/dev/mtdblock6 rootwait console=ttyS4,115200
>> earlycon=uart8250,mmio32,0x1e784000,115200n8" \
>>> -dtb arch/arm/boot/dts/aspeed/aspeed-bmc-supermicro-x11spi.dtb
>> \
>>> -nographic -monitor null -serial stdio
>>>
>>> This is with aspeed_g5_defconfig. Note that the flash models need to be
>> specified.
>>> The default flashes are no longer recognized when booting from qemu since
>> commit
>>> 947c86e481a0 ("mtd: spi-nor: macronix: Drop the redundant flash info
>> fields").
>>>
>>> The above only works with this patch reverted (or with v6.15 and older, of
>> course).
>>>
>>> Guenter
>>
>> Alexander, can you please investigate? We need a fix because Guenter
>> might not be the only affecter user. Otherwise this patch can't stand,
>> unfortunately.
>>
>> Thanks,
>> Miquèl
>
> Maybe something is moved, and it is not /dev/mtdblock6 now.
>

With this patch:

# ls -l /dev/*mtd*
crw------- 1 root root 90, 0 Jan 1 00:00 /dev/mtd0
crw------- 1 root root 90, 1 Jan 1 00:00 /dev/mtd0ro
crw------- 1 root root 90, 2 Jan 1 00:00 /dev/mtd1
crw------- 1 root root 90, 3 Jan 1 00:00 /dev/mtd1ro
crw------- 1 root root 244, 0 Jan 1 00:00 /dev/mtd_master0
crw------- 1 root root 244, 1 Jan 1 00:00 /dev/mtd_master1
brw------- 1 root root 31, 0 Jan 1 00:00 /dev/mtdblock0
brw------- 1 root root 31, 1 Jan 1 00:00 /dev/mtdblock1
~ # ls /proc/mtd
/proc/mtd
~ # cat /proc/mtd
dev: size erasesize name
mtd0: 02000000 00010000 "bmc"
mtd1: 02000000 00010000 "pnor"

After reverting it:

# ls -l /dev/mtd*
crw------- 1 root root 90, 0 Jan 1 00:00 /dev/mtd0
crw------- 1 root root 90, 1 Jan 1 00:00 /dev/mtd0ro
crw------- 1 root root 90, 2 Jan 1 00:00 /dev/mtd1
crw------- 1 root root 90, 3 Jan 1 00:00 /dev/mtd1ro
crw------- 1 root root 90, 4 Jan 1 00:00 /dev/mtd2
crw------- 1 root root 90, 5 Jan 1 00:00 /dev/mtd2ro
crw------- 1 root root 90, 6 Jan 1 00:00 /dev/mtd3
crw------- 1 root root 90, 7 Jan 1 00:00 /dev/mtd3ro
crw------- 1 root root 90, 8 Jan 1 00:00 /dev/mtd4
crw------- 1 root root 90, 9 Jan 1 00:00 /dev/mtd4ro
crw------- 1 root root 90, 10 Jan 1 00:00 /dev/mtd5
crw------- 1 root root 90, 11 Jan 1 00:00 /dev/mtd5ro
crw------- 1 root root 90, 12 Jan 1 00:00 /dev/mtd6
crw------- 1 root root 90, 13 Jan 1 00:00 /dev/mtd6ro
brw------- 1 root root 31, 0 Jan 1 00:00 /dev/mtdblock0
brw------- 1 root root 31, 1 Jan 1 00:00 /dev/mtdblock1
brw------- 1 root root 31, 2 Jan 1 00:00 /dev/mtdblock2
brw------- 1 root root 31, 3 Jan 1 00:00 /dev/mtdblock3
brw------- 1 root root 31, 4 Jan 1 00:00 /dev/mtdblock4
brw------- 1 root root 31, 5 Jan 1 00:00 /dev/mtdblock5
brw------- 1 root root 31, 6 Jan 1 00:00 /dev/mtdblock6
~ # cat /proc/mtd
dev: size erasesize name
mtd0: 02000000 00010000 "bmc"
mtd1: 00060000 00010000 "u-boot"
mtd2: 00020000 00010000 "u-boot-env"
mtd3: 00440000 00010000 "kernel"
mtd4: 01740000 00010000 "rofs"
mtd5: 00400000 00010000 "rwfs"
mtd6: 02000000 00010000 "pnor"

I am trying to boot from "pnor". It looks like the partition data (from devicetree)
is now ignored. mtdblock6 used to be the second flash.

Guenter