Re: [GIT preview] for-6.3/cxl-ram-region

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Mon, 2023-01-30 at 21:00 -0500, Gregory Price wrote:
> On Mon, Jan 30, 2023 at 03:18:38PM -0800, Dan Williams wrote:
> 
> 
> This worked for me, though it took me a bit to figure out how to wire
> everythign up - still not sure this is entirely correct but this is the
> string of commands that were required to successfully attach an endpoint
> decoder to the root decoder.
> 
> Note: The root decoder has interleave_(granularity=256, ways=1), and the
> region code appears to require the same granularity?  Does that mean
> we're stuck to 256b granularity? (unless i misread the code, which i'm
> about 75% sure i am).
> 
> 
> Command string:
> 
> # Program the endpoint decoder for ram of size 1GB
> echo ram > /sys/bus/cxl/devices/decoder2.0/mode
> echo 0x40000000 > /sys/bus/cxl/devices/decoder2.0/dpa_size
> 
> # Create a region in the root decoder
> echo region0 > /sys/bus/cxl/devices/decoder0.0/create_ram_region
> 
> # Configure that region with the same interleave granularity
> # and ways as the root and endpoint decoders
> echo 256 > /sys/bus/cxl/devices/region0/interleave_granularity
> echo 1 > /sys/bus/cxl/devices/region0/interleave_ways
> echo 0x40000000 > /sys/bus/cxl/devices/region0/size
> 
> # Link the endpoint decoder as a target in the region
> echo decoder2.0 > /sys/bus/cxl/devices/region0/target0
> 
> # Commit the changes
> echo 1 > /sys/bus/cxl/devices/region0/commit

I've pushed a cxl-cli branch[1] that incorporates this flow, and allows
for: cxl create-region -t ram <other options>

Feel free to give it a spin!

[1]: https://github.com/pmem/ndctl/commits/vv/volatile-regions