Re: [PATCH 12/14] net: axienet: Autodetect 64-bit DMA capability

On Fri, 10 Jan 2020 15:08:52 +0100
Andrew Lunn [off-list ref] wrote:

Hi Andrew,

thanks for having a look!

quoted

To autodetect this configuration, at probe time we write all 1's to such
an MSB register, and see if any bits stick.  

So there is no register you can read containing the IP version?

There is, and I actually read this before doing this check. But the 64-bit DMA capability is optional even in this revision. It depends on what you give it as the address width. If you say 32, the IP config tool disables the 64-bit capability completely, so it stays compatible with older revisions.
Anything beyond 32 will enable the MSB register and will also require you to write to them.

Cheers,
Andre