[Skiboot] [RFC 0/3] phb4/capp: Provide user tunable for STQ/DMA engine allocation

Vaibhav Jain vaibhav at linux.ibm.com
Mon Sep 10 15:23:59 AEST 2018

Thanks for looking into these patches Andrew,

Andrew Donnellan <andrew.donnellan at au1.ibm.com> writes:

> While NVRAM attributes might be a good idea for bringup/enablement 
> environments I think it's not ideal for doing device-specific 
> configuration in production environments.
This is more likely AFU specific rather than device specific. Since the
split between coherent/dma traffic might be specific to an AFU hence its
difficult to comeup with an optimal default.

> Would it be possible to expose this to Linux in the form of an 
> additional OPAL API call, or does this need to be determined too early 
> in the process? That would allow the allocation to be determined by the 
> driver, where it's easier to add device-specific quirks.
Yes, but presently opal_pci_set_phb_capi_mode() is too restrictive and
we may need to add a new opal call to enable capi mode and providing it
with necessary info based on device quirks. But then too, it might not
be optimal for certain AFUs.

> -- 
> Andrew Donnellan              OzLabs, ADL Canberra
> andrew.donnellan at au1.ibm.com  IBM Australia Limited

Vaibhav Jain <vaibhav at linux.vnet.ibm.com>
Linux Technology Center, IBM India Pvt. Ltd.

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