[PATCH v1 08/22] siemens: capricorn: use DCD_SKIP entry

[Heiko Schocher]

Hello Wolater,

On 11.11.24 09:35, Schweizer, Walter wrote:
> On Fri, 2024-11-08 at 06:21 +0100, Heiko Schocher wrote:
>> Boards which use DCD data in SCFW can drop SPL.
>>
>> We tried in our mainline rework to use this approach
>> too as other imx8qxp boards do in mainline. But we
>> failed ... it was a hard way to understand the
>> reason!
>>
>> We cannot use DCD image in container as the SCFW
>> from siemens, does the RAM init on boot itself!
>>
>> Siemens SCFW reads the RAM config from i2c eeprom and
>> dependent on this settings, initializes the RAM.
>>
>> Adding DCD data to the bootcontainer will result in
>> hang of the SCFW, also DCD data in container image is
>> static which do not fit our needs.
>>
>> So we must drop DCD data image, and this has the side
>> effect that we need SPL, as the task which loads the images
>> from the container only loads the images to addresses,
>> and if executed bit is set, starts them.
>>
>> As now RAM is not initialized from it, and there is no
>> option to "wait until SCFW has setup RAM",  we can only
>> load SPL into internal RAM at this point, as than SPL
>> and SCFW boot parallel.
>>
>> The SPL itself than uses the SCU API to communicate
> 
> I think there is a typo "than" should be "then"?

Fixed, thanks!

bye,
Heiko
> 
>> with the SCFW and it seems that SCFW only responds to
>> this API requests when RAM setup is already done by the
>> SCFW, which has a side-effect of a "sync" for the RAM
>> setup is done by SCFW!
>>
>> We checked if SPL is always save in accessing RAM for
>> loading images to it! For tests, we added in our RAM
>> init part in the SCFW long delays (10 seconds and more)
>> as we thought there is such a sync missing, and we can
>> break the board through delaying RAM setup... but we
>> did not managed to fail booting U-Boot from SPL!
>>
>> Signed-off-by: Heiko Schocher <hs at denx.de>
>> ---
>>
>>   board/siemens/capricorn/imximage.cfg | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/board/siemens/capricorn/imximage.cfg
>> b/board/siemens/capricorn/imximage.cfg
>> index 4350e2967cc..e45f2c9589e 100644
>> --- a/board/siemens/capricorn/imximage.cfg
>> +++ b/board/siemens/capricorn/imximage.cfg
>> @@ -9,6 +9,10 @@
>>   
>>   /* Boot from SD, sector size 0x400 */
>>   BOOT_FROM      sd
>> +
>> +/* skip DCD data, as firmware initializes the RAM */
>> +DCD_SKIP true
>> +
>>   /* SoC type IMX8QX */
>>   SOC_TYPE IMX8QX
>>   /* Append seco container image */
> 

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