[RFC] AMD polaris MEM_AP_SIZE location (PCI BAR aperture size)

Christian K├Ânig ckoenig.leichtzumerken at gmail.com
Wed Aug 28 08:31:43 UTC 2019


Hi Petr,

well that is indeed a rather unusual use case.

I'm not 100% sure how you actually hacked the HD4550 to do what you want 
to do, cause this ASIC generation shouldn't support this.

For a Polaris you can just use the PCIe resizeable BAR extension. For 
how to use it see the pci_resize_resource() function in the linux kernel.

Please be aware that we usually use the function to increase the BAR 
size to allow the CPU to access more of the on board memory, so making 
it smaller might actually not be tested at all.

Regards,
Christian.


Am 27.08.19 um 04:36 schrieb Petr Cvek:
> Hello,
>
> I'm trying to run AMD GPUs in unusual configurations. I was able to decrease the PCI BAR size in HD4550 by its BIOS strap configuration and change it to 64MB (and I was able to run it on MIPS vocore2 board :-D ). Is there a similar configuration location for AMD polaris 11/RX 460 BIOS?
>
> Petr Cvek
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