[U-Boot] DA850evm SPI Flash Partitions between Linux and U-boot are Inconsistent

[Adam Ford]

On Wed, Aug 30, 2017 at 12:30 AM, Sekhar Nori <nsekhar at ti.com> wrote:
> On Wednesday 30 August 2017 08:07 AM, Adam Ford wrote:
>> On Tue, Aug 29, 2017 at 8:05 AM, Adam Ford <aford173 at gmail.com> wrote:
>>> On Tue, Aug 29, 2017 at 6:41 AM, Sekhar Nori <nsekhar at ti.com> wrote:
>>>> On Tuesday 29 August 2017 03:29 PM, Adam Ford wrote:
>>>>> On Tue, Aug 29, 2017 at 4:13 AM, Sekhar Nori <nsekhar at ti.com> wrote:
>>>>>> Hi Adam,
>>>>>>
>>>>>> On Sunday 27 August 2017 08:31 PM, Adam Ford wrote:
>>>>>>> I was trying to enable MTD Partitions to make loading the Kernel and
>>>>>>> FS easier from within U-Boot
>>>>>>>
>>>>>>> The da850evm spi-flash partitions in Linux show
>>>>>>>
>>>>>>> "U-Boot-SPL" @ offset 0, size 64K
>>>>>>> "U-Boot"; @ offset 0x00010000, size 512K
>>>>>>> "U-Boot-Env"; @ offset 0x00090000
>>>>>>
>>>>>> According to board/davinci/da8xxevm/README.da850, we support AIS image
>>>>>> format for SPI boot. This is a single image containing SPL and U-Boot.
>>>>>>
>>>>>> Given this, I think having separate partitions for SPL and U-Boot does
>>>>>> not make sense since thats not how its going to be used.
>>>>>
>>>>> That's what I was thinking too, but I wasn't sure if someone had split
>>>>> SPL somehow to make it possible to update U-Boot via Linux or U-Boot
>>>>> itself.
>>>>>>
>>>>>>>
>>>>>>> However U-Boot shows the following:
>>>>>>>
>>>>>>> CONFIG_SYS_SPI_U_BOOT_OFFS 0x8000 which would make the SPL partition 32K.
>>>>>>> CONFIG_SYS_SPI_U_BOOT_SIZE      0x40000 and the size of U-boot 256K
>>>>>>> instead of 512k.
>>>>>>>
>>>>>>> CONFIG_ENV_SIZE                 (64 << 10)
>>>>>>> CONFIG_ENV_OFFSET           (512 << 10) which is 0x80000 instead of
>>>>>>> Linux's 0x90000
>>>>>>>
>>>>>>> It seems to me like the U-Boot and Linux should try and synchronize
>>>>>>> their partitions tables.
>>>>>>
>>>>>> Right.
>>>>>>
>>>>>>> For people who want to burn Linux into the SPI flash it seems there
>>>>>>> there should be some consistency.  I tried making the U-boot settings
>>>>>>> match the Linux ones, but it seems to hang between SPL and U-Boot, so
>>>>>>> I think the U-Boot offset in Linux might need to match U-Boot.  Can
>>>>>>> you guys make some recomendations as to which is correct?
>>>>>>
>>>>>> I have not tried it, but looks like the partitions we need are
>>>>>>
>>>>>> "SPL/U-Boot AIS" @ offset 0, size 512K
>>>>>> "U-Boot Environment" @ offset 512K, size 64K
>>>>>
>>>>> I was thinking the same thing.
>>>>>
>>>>>> "Kernel/Spare" @ offset 576K, size 7552K
>>>>>> "Mac Address" @ offset 8128K, size 64K (read only)
>>>>>
>>>>> If U-Boot reads the MAC address from its environmental variables
>>>>> instead of using up an entire 64K for what conceivably is 6 bytes,
>>>>> could we free up this space to help grow the Kernel/Spare space?
>>>>
>>>> If environment sector is erased, the mac address needs to be restored
>>>> from SPI flash. Thats why I think it needs to remain as a read-only
>>>> partition. Also, its just 64K more space, not sure if it will make a big
>>>> difference in the overall scheme of things.
>>>>
>>>>>> With an 8M flash, I think its futile to try to fit a modern filesystem
>>>>>> on the flash.
>>>>>>
>>>>>> If you are using DT boot, we cannot really change the partitions in
>>>>>> device-tree because of DT backward-compatibility requirements. But we
>>>>>> can fix da850evm_spiflash_part[] table in
>>>>>> arch/arm/mach-davinci/board-da850-evm.c.
>>>>>
>>>>> Wouldn't having two different partition tables between da850-evm.c and
>>>>> the DT cause confusion down the road?  With DT being the future, why
>>>>> would we not try to eliminate any custom board files with just a
>>>>> single common davinci board file + board specific DT?
>>>>
>>>> Thats ideal yes. But there is a lot of support in the da850-evm board
>>>> file which does not have a DT equivalent yet. Thats why I have kept the
>>>> board file around.
>>>>
>>>>>> To help DT boot, we can pass fixed up mtdparts through environment
>>>>>> variables. Something like what is done in 3f18ff07c81b ("ARM: keystone:
>>>>>> Pass SPI MTD partition table via kernel command line").
>>>>>
>>>>> This was ultimately was I was wanting to do.  For some of the OMAP3
>>>>> boards, removing the partition tree was accepted since the partition
>>>>> info was passed to the kernel.  If we did this for DA850, we could
>>>>> simply elimiate the partition info in the Kernel (like some of the
>>>>> omap3 boards) and let the partition maps be defined by U-Boot would
>>>>> would guarantee consistency between them.
>>>>
>>>> Actually, thinking a bit more, we cannot change the partition
>>>> information in kernel at all since that means loss of data for anyone
>>>> updating just the kernel.
>>>>
>>>> We can however, pass updated kernel command line arguments in U-Boot so
>>>> anyone updating the bootloader and erasing the environment sector gets
>>>> updated partition information. This is likely to be the case where
>>>> entire flash is being re-written and loss of data is not a concern.
>>>>
>>> That makes sense to me.
>>>
>>> I'll send a U-Boot patch marked RFC later today with the MTD stuff
>>> enabled in U-Boot and changes to the bootargs to pass the MTD
>>> information to Linux.
>>>
>>
>> I have a patch ready for review for U-Boot, but I had to make a few
>> changes to the davinci_all_defconfig to get the MTD partitions to map
>> correctly:
>>
>> -CONFIG_MTD=m
>> +CONFIG_MTD=y
>
> Hmm. why the shift to built-in for MTD?

I was concerned about the order that the modules were being loaded.
Having MTD set to Y is required if MTD_CMDLINE_PARTS is set to Y, and
that guarantees that the CMDLINE_PARTS will load before the spi flash
module. I wanted to make sure the partition table from U-Boot was
passed instead the the default one in Linux and I didn't see any other
way.  I have a rootfs using eudev to load kernel modules, and it
doesn't always seem to load stuff in a consistent order.

>
>>  CONFIG_MTD_TESTS=m
>> +CONFIG_MTD_CMDLINE_PARTS=y
>
> This should be module as well.
>
>> +CONFIG_MTD_OF_PARTS=m
>>
>>
>> Are you OK with that?  If so, I'll push a formal patch to Linux and
>> then submit a subsequent patch for U-Boot marked RFC with MTD parts
>> and CMD stuff enabled to pass the MTD partition info to Linux.
>
> Sounds good.
>
>>
>> Currently, I have it defined as:
>> mtdparts=spi0.0:512k(u-boot.ais),64k(u-boot-env),7552k(kernel-spare),64k(MAC-Address)
>>
>> Does that work for you?
>
> Looks good to me!
>
> Thanks,
> Sekhar
thanks,

adam