DTB_RESELECT/MULTI DTB with SPL flow

DTB_RESELECT/MULTI DTB with SPL flow

[Michal Simek]

Hi,

I am just trying to wrap my head around DTB_RESELECT feature.
ZynqMP is using u-boot.itb which is u-boot/atf + a lot of DT files.
As of now SPL should pick the right one load it predefined location
which U-Boot proper pickup.
Others DTBs are not loaded at all.
This is working fine and I expect it should work like this even with
DTB_RESELECT enabled because you need to have base DTB for being able to
do platform detection.
I have hookup platform detection in embedded_dtb_select and I know which
board revision I am running at and struggling how to tell u-boot what to do.

What should be the right flow for changing DTB at run time?
Where they should be stored? I would expect that I need to have FIT
image in memory for all board revisions and u-boot should be calling
board_fit_config_name_match() which will decide which DT is correct
based on board detection done in embedded_dtb_select().

Thanks,
Michal

Re: DTB_RESELECT/MULTI DTB with SPL flow

[Simon Glass]

Hi Michal,

On Fri, 11 Jun 2021 at 07:56, Michal Simek <michal.simek@xilinx.com> wrote:
>
> Hi,
>
> I am just trying to wrap my head around DTB_RESELECT feature.

Did you intend to cc the author of that?

Does doc/README.multi-dtb-fit help?

> ZynqMP is using u-boot.itb which is u-boot/atf + a lot of DT files.
> As of now SPL should pick the right one load it predefined location
> which U-Boot proper pickup.
> Others DTBs are not loaded at all.
> This is working fine and I expect it should work like this even with
> DTB_RESELECT enabled because you need to have base DTB for being able to
> do platform detection.
> I have hookup platform detection in embedded_dtb_select and I know which
> board revision I am running at and struggling how to tell u-boot what to do.
>
> What should be the right flow for changing DTB at run time?
> Where they should be stored? I would expect that I need to have FIT
> image in memory for all board revisions and u-boot should be calling
> board_fit_config_name_match() which will decide which DT is correct
> based on board detection done in embedded_dtb_select().

Yes you can use a FIT to hold the DTs. You can also use binman I
suppose (the 'files' entry type perhaps).

Regards,
Simon

Re: DTB_RESELECT/MULTI DTB with SPL flow

[Michal Simek]

Hi Simon,


On 6/26/21 8:30 PM, Simon Glass wrote:
> Hi Michal,
> 
> On Fri, 11 Jun 2021 at 07:56, Michal Simek <michal.simek@xilinx.com> wrote:
>>
>> Hi,
>>
>> I am just trying to wrap my head around DTB_RESELECT feature.
> 
> Did you intend to cc the author of that?
> 
> Does doc/README.multi-dtb-fit help?
> 
>> ZynqMP is using u-boot.itb which is u-boot/atf + a lot of DT files.
>> As of now SPL should pick the right one load it predefined location
>> which U-Boot proper pickup.
>> Others DTBs are not loaded at all.
>> This is working fine and I expect it should work like this even with
>> DTB_RESELECT enabled because you need to have base DTB for being able to
>> do platform detection.
>> I have hookup platform detection in embedded_dtb_select and I know which
>> board revision I am running at and struggling how to tell u-boot what to do.
>>
>> What should be the right flow for changing DTB at run time?
>> Where they should be stored? I would expect that I need to have FIT
>> image in memory for all board revisions and u-boot should be calling
>> board_fit_config_name_match() which will decide which DT is correct
>> based on board detection done in embedded_dtb_select().
> 
> Yes you can use a FIT to hold the DTs. You can also use binman I
> suppose (the 'files' entry type perhaps).

I got it working. Also found one alignment issue which needs to be
fixed. And also DT overlays are not supported now.

Thanks,
Michal