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

[Schweizer, Walter]

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"?

> 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 */

-- 
Walter Schweizer
Siemens AG
www.siemens.com