[OpenPOWER-HDL-Cores] u-boot for openpower

Benjamin Herrenschmidt benh at kernel.crashing.org
Mon May 10 05:27:28 UTC 2021


On Thu, 2021-05-06 at 05:59 +0100, Luke Kenneth Casson Leighton wrote:
> garding submitting litedram sdram_init upstream to u-boot, your
> concern was that this is so device specific that you felt it
> inappropriate
> 
> i thought about this, and realised, "news flash: *all* u-boot bare
> metal cold start initialisation is device-specific"!
> 
> :)

We are familiar with u-boot and bare metal initializations. The problem
here is that sdram_init is partially auto-generated and based on
whatever changes are happening in LiteX upstream which is still quite a
moving target.

That said, since we do commit in microwatt a specific generated
version, we could just enforce that we don't update it unless strictly
necessary since such an update might require a corresponding u-boot
change.

Additionally, LiteDRAM inits are specific to a given FPGA config.

It would probably be nicer if LiteDRAM inits could be refactored in a
more data-driven way such that some kind of very compact table gets
stored in a block "ROM" in the FPGA and a slightly more generic init
code follows it.

Cheers,
Ben.




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