[PATCH] doc: rockchip: Clarify the rkspi image format further

[Johan Jonker]

On 2/10/24 19:18, Dragan Simic wrote:
> As discussed on the U-Boot mailing list, [1][2] only some Rockchip SoCs
> suffer from a bug in their BROMs that requires a specific format for their

This not a bug.

> SPI images, which was the reason for the rkspi format to be introduced.
> 
> Improve the description of the rkspi format a bit to mention this, for
> future reference and to make understanding it easier.
> 
> [1] https://lore.kernel.org/u-boot/c32129ba-db25-4b9d-9a4a-032d88dfb9cd@kwiboo.se/
> [2] https://lore.kernel.org/u-boot/CACdvmAjfCWicRd=LKKyob7fZo79AFkUQKy0e1HBb0zyJuoO70g@mail.gmail.com/
> 
> Signed-off-by: Dragan Simic <dsimic at manjaro.org>
> ---
>  doc/README.rockchip | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/README.rockchip b/doc/README.rockchip
> index 84caff8a24d3..e0c5c395ec6a 100644
> --- a/doc/README.rockchip
> +++ b/doc/README.rockchip
> @@ -649,7 +649,12 @@ sector is used. The header is the same as with rksd and the maximum size is

>  also 32KB (before spreading). The image should be written to the start of
>  SPI flash.
>  

On rk3066 an image should start before page address:
NAND : 50
SPI  : 13
EMMC :  1

Not sure about start limits for other SoC's. (Kever ??)

Also rk3066 and rk3188 use RC4 crypto.

> -See above for instructions on how to write a SPI image.
> +Only the BROMs of some Rockchip SoCs, such as the RK3399, suffer from a bug
> +that mandates the above-described data spreading, thus requiring the rkspi
> +format to be used for their SPI images. Rockchip SoCs that don't suffer
> +from this bug use the rksd format for their SPI images.
> +

This not a bug. It's a design choice to reuse the reading function in the boot ROM shared by EMMC, NAND and SPI etc. due to size restrictions.

See NAND example:
https://source.denx.de/u-boot/custodians/u-boot-rockchip/-/blob/master/drivers/block/rkmtd.c?ref_type=heads#L259

This NAND code also applies to SPI with minor tweaks.
Code will never read more then 2k regardless of the page size.

===
This info must be written in a more neutral wording.(no bugs involved)
Just describe the 2 formats and the SoC's that use it.

Johan

===
Extra:

Could someone cleanup README.rockchip
The file README.rockchip has most building scenarios covered by now.
Please have a look if all the boot log listing in that file are still needed or can be removed. 

===

Is there a need for SPI programmer code a la RKMTD with common base and block interface tools?

===

Is someone able to extract rk3568 boot ROM code in order to study NAND boot behavior for a future RKMTD NFC V9 upgrade?

> +See the section above for instructions on how to write an SPI image.
>  
>  rkmux.py
>  --------
>