[U-Boot] [PATCH 0/3] imx: bootaux elf firmware support

[Stefan Agner]

Hi Lukasz,

On 2017-04-03 04:20, Lukasz Majewski wrote:
> Hi Stefan,
> 
> Thanks for your patch. Please allow me to share some ideas for
> improvements.
> 
>> From: Stefan Agner <stefan.agner at toradex.com>
>>
>> This patchset enables to boot elf binaries on secondary Cortex-M
>> class cores available on i.MX 6SoloX/7Solo/7Dual. This makes
>> handling and loading firmwares much more convinient since all
>> information where the firmware has to be loaded to is contained in
>> the elf headers. A typical usage looks like this:
>>
>>   Colibri iMX7 # tftp ${loadaddr} firmware.elf && bootaux ${loadaddr}
>>   Using FEC0 device
>>   TFTP from server 192.168.10.1; our IP address is 192.168.10.2
>>   Filename 'firmware.elf'.
>>   Load address: 0x80800000
>>   Loading: ##################################################  88.3
>> KiB 5.4 MiB/s
>>   done
>>   Bytes transferred = 90424 (16138 hex)
>>   ## Starting auxiliary core at 0x1FFF8311 ...
>>   Colibri iMX7 #
> 
> I can find some other platforms (not only IMX), which would benefit
> from this code - the generic 'bootaux' command.
> 
> One good example would to allow multiple binaries for different SoC
> Cores (e.g. 2x Cortex-A8) to be loaded and started by u-boot.
> 
> Hence, I'm wondering if you could make those patches usable for other
> platforms as well?

I don't think that this is a good idea. bootaux is meant for auxiliary
cores, which often use a different architecture and are not cache
coherent (hence the cache flushes).

On SMP systems the main operating system normally starts the secondary
core. Otherwise, if you want to run them separately using U-Boot, maybe
a new command such as bootsmp would be more suited.

> 
>>
>> Note that the bootaux command retrieved the entry point (PC) from
>> the elf binary.
> 
> Could you make this code flexible enough to handle not only elf
> binaries, but also other data (e.g. FPGA bitstreams)?

The code of bootaux is rather small, I don't see much value into stuff
boot code for other peripherals into it. I don't know how FPGA bistream
loading typically works, but I guess it is quite different from loading
a firmware into RAM/SRAM and flush caches...

I am not against reuse and unification, I just feel that this is not
really a case where we gain much.

> 
> Maybe it would better to:
> -------------------------
> 
> Embrace those binaries into FIT file (*.itb)? And allow multiple
> binaries loading? I'm thinking of work similar to one already did by
> Andre Przywara for SPL:
> 
> "[PATCH v3 00/19] SPL: extend FIT loading support" posted on 31.03.2017?
> 
> In that way we would "open" many new use cases, and other platforms
> (e.g. FPGA's, TI, etc) could benefit from it. 
> One solid use case is to load different Linux binaries (or/and bare
> metal programs) to different SoC cores.
> 
> The "meta data" (i.e. load address, data type, description), could be
> extracted from the FIT format (the code is already in u-boot).
> 
> IMHO, this is very generic approach.

I did some experiments with using FIT images for auxiliary core
firmware, however, it did not add a lot of advantage over using elf:
http://git.toradex.com/cgit/u-boot-toradex.git/commit/?h=2015.04-toradex-next&id=d1d416f272e840e8139aec911f89a70fe5523eb2

Firmwares are already built and available in the elf file format. The
Linux remoteproc framework, which is meant to handle this kind of cores
too, supports elf firmware loading too, so supporting elf in U-Boot too
is a nice alignment. Also using FIT adds an additional step when
building firm wares...


> 
>> Also all sections are translated to A7 addresses
>> in order to properly load the firmware sections into the appropriate
>> locations.
> 
> This would require some tiny arch specific code.
> 

Yes, but in my rather small patchset (164 additional lines) this is
actually almost the bulk of changes :-)

--
Stefan

>> Also cache flushes is taken care of, so that there is no
>> manual dcache flush necessary anymore.
>>
>> The NXP FreeRTOS BSP already generates elf binaries which can be
>> directly used with this elf binary support.
>>
>> The last patch adds bootaux support for Vybrid.
>>
>>
>> Stefan Agner (3):
>>   imx: imx-common: move aux core image parsing to common code
>>   imx: imx-common: add elf firmware support
>>   ARM: vf610: add auxiliary core boot support
>>
>>  arch/arm/cpu/armv7/mx6/soc.c                |  30 +++++---
>>  arch/arm/cpu/armv7/mx7/soc.c                |  34 ++++++---
>>  arch/arm/cpu/armv7/vf610/generic.c          |  42 +++++++++++
>>  arch/arm/imx-common/Kconfig                 |   2 +-
>>  arch/arm/imx-common/Makefile                |   4 +-
>>  arch/arm/imx-common/imx_bootaux.c           | 105
>> +++++++++++++++++++++++-----
>> arch/arm/include/asm/arch-vf610/sys_proto.h |   8 +++
>> arch/arm/include/asm/imx-common/sys_proto.h |   6 ++
>> configs/colibri_vf_defconfig                |   1 + 9 files changed,
>> 198 insertions(+), 34 deletions(-) create mode 100644
>> arch/arm/include/asm/arch-vf610/sys_proto.h
>>
> 
> 
> 
> 
> Best regards,
> 
> Lukasz Majewski
> 
> --
> 
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