Re: [PATCH v2] ARM: i.MX8M: esdctl: split memory banks for devices with >4G

[Sascha Hauer <sha@pengutronix.de>]

Hi Marco,

On Thu, Aug 31, 2023 at 04:47:24PM +0200, Marco Felsch wrote:
> At the moment the whole available memory is added to one single memory
> bank "ram0". This can cause barebox chainload issues on devices with a
> huge amount of memory like the i.MX8MP-EVK which has 6G of RAM if the
> barebox pbl binary is to large.
> 
> The reason for this issues is that memory_bank_first_find_space()
> returns the memory area with the largest amount of free space on the
> first memory bank. So in case of Debix SOM-A 8G and i.MX8MP-EVK 6G this
> is the area crossing the 4G boundary. This cause the barebox pbl code to
> trigger a MMU exception once the early MMU gets enabled which is
> configured for sizes <=4G.
> 
> Split the memory space into two memory banks: "ram0" and "ram1" to fix
> this issue.

In the long run we'll need a proper solution for this. I think this
patch is fine for now, but please add a comment why we are doing this.
Otherwise we might remove this superfluous code at some point.

Sascha

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