[PATCH] rpi: always set fdt_addr with firmware-provided FDT address

[Mauro Salvini]

Hi Matthias

On 15/09/21 13:16, mbrugger at suse.com (Matthias Brugger) wrote:
> Hi Mauro,
> 
> On 07/06/2021 11:27, Mauro Salvini wrote:
>> On 12/05/21 14:39, Mauro Salvini wrote:
>>> Raspberry firmware prepares the FDT blob in memory at an address
>>> that depends on both the memory size and the blob size [1].
>>> After commit ade243a211d6 ("rpi: passthrough of the firmware provided FDT
>>> blob") this FDT is passed to kernel through fdt_addr environment variable,
>>> handled in set_fdt_addr() function in board file.
>>>
>>> When u-boot environment is persistently saved, if a change happens
>>> in loaded FDT (e.g. for a new overlay applied), firmware produces a FDT
>>> address different from the saved one, but u-boot still use the saved
>>> one because set_fdt_addr() function does not overwrite the fdt_addr
>>> variable. So, for example, if there is a script that uses fdt commands for
>>> e.g. manipulate the bootargs, boot hangs with error
>>>
>>> libfdt fdt_check_header(): FDT_ERR_BADMAGIC
>>>
>>> Removing the fdt_addr variable in saved environment allows to boot.
>>>
>>> With this patch set_fdt_addr() function always overwrite fdt_addr value.
>>>
>>> [1] https://www.raspberrypi.org/forums//viewtopic.php?f=107&t=134018
>>>
> 
> First of all sorry for the very late reply.
> I'm hesitant to apply this patch, basically because it can break other setups
> where people load a custom DTB to fdt_addr.
> 
> I wonder why you can't erase fdt_addr from your persistent storage. There is a
> command called eraseenv that should to the job.

Sorry me too for the late reply.

So your suggestion is to erase the fdt_addr variable from the 
environment each time one needs to "refresh" it (one example could be 
the situation that I ponted out).

Yes, this could be the solution, but the need to delete the fdt_addr 
variable when e.g. one changes the dtb loaded by rpi firmware should be 
documented somewhere.

Thanks, regards
Mauro

> 
> Regards,
> Matthias
> 
>>> Signed-off-by: Mauro Salvini <m.salvini at koansoftware.com>
>>> Cc: C?dric Schieli <cschieli at gmail.com>
>>> Cc: Matthias Brugger <mbrugger at suse.com>
>>> ---
>>> ? board/raspberrypi/rpi/rpi.c | 3 ---
>>> ? 1 file changed, 3 deletions(-)
>>>
>>> diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
>>> index df52a4689f..611013471e 100644
>>> --- a/board/raspberrypi/rpi/rpi.c
>>> +++ b/board/raspberrypi/rpi/rpi.c
>>> @@ -318,9 +318,6 @@ static void set_fdtfile(void)
>>> ?? */
>>> ? static void set_fdt_addr(void)
>>> ? {
>>> -??? if (env_get("fdt_addr"))
>>> -??????? return;
>>> -
>>> ????? if (fdt_magic(fw_dtb_pointer) != FDT_MAGIC)
>>> ????????? return;
>>>
>>
>>
>> Hi all,
>>
>> kind ping.
>>
>> Regards
>>


-- 
Mauro Salvini | KOAN sas | Bergamo - Italia
embedded software engineering
Phone: +39 035-255235
http://KoanSoftware.com