Re: [PATCH v3 4/4] pdx: Add CONFIG_PDX_COMPRESSION as a common Kconfig option

[Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>]

On 9/22/23 3:03 PM, Andrew Cooper wrote:
> Several things.
> 
> First, Shawn: PPC has gained a HAS_PDX, the deletion of which needs
> merging into this patch.
> 
> It was added as part of 4a2f68f909304 which was "minimal to build". 
> This series address the issue you presumably encountered where pdx.c
> appears to be optional but wasn't.
>

That's correct, build was broken without HAS_PDX.

> 
> Do PPC platforms have (or potentially have) sparse RAM banks?
>

Yes, they do. Especially on POWER9, it is very common for there to be
large gaps in the physical address space between RAM banks.

> If like x86 the answer is definitely no, then you want to have
> PDX_COMPRESSION=n
> 
> If the answer is definitely yes always, then you want PDX_COMPRESSION=y
>
> If the answer is system specific, then you want to offer users a choice.

It looks like PDX_COMPRESSION=y would probably make the most sense for
ppc, but I'm not against making it a choice.

Thanks,
Shawn