Re: [PATCH] cxl/hdm: Avoid DVSEC fallback after region teardown

[Dan Williams]

Koralahalli Channabasappa, Smita wrote:
[..]
> > "do not teardown auto regions" should squash this crop of setup bugs.
> 
> Looking at this more closely for patch 2, if I'm not wrong, I think the 
> problem is that cxl_setup_hdm_decoder_from_dvsec() is not setting up the 
> interleave_granularity on the decoder. It inherits the default PAGE_SIZE 
> (4096) from cxl_decoder_init(), and construct_region() then copies that 
> stale value into the region params.
> 
> So even in a DVSEC emulation case, the IG would be whatever 
> cxl_decoder_init() defaulted to, not what the actual configuration is right?

Remember that CXL 1.1 DVSEC range registers do not support interleave.
Interleaving was a CXL 2.0 feature.

So in the case where HDM decoders are actually disabled and DVSEC Range
registers are sufficient, the bug is in cxl_port_setup_targets().
Specifically, when interleave_ways == 1 then interleave_granularity does
not matter. It is ok for CFMWS and the region granularity numbers to
mismatch in that case.

So I would not expect that ig mismatch matters after:

ce32b0c9c522 cxl: core/region - ignore interleave granularity when ways=1

...did that miss an additional location where we are doing granularity
checks?

> Is the second patch about fixing cxl_setup_hdm_decoder_from_dvsec() to 
> properly set the interleave granularity?

I would say just clean up the changelog per the feedback and we can
start a separate thread to fixup DVSEC support.

With the suggested changelog updates you can also add:

Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>