Re: [PATCH] cxl/region: Allow 6 & 12 way regions on 3-way HB interleaves

[Alison Schofield <alison.schofield@intel.com>]

On Wed, Feb 26, 2025 at 03:12:46PM +0800, Li Ming wrote:
> On 2/25/2025 7:58 AM, alison.schofield@intel.com wrote:
> > From: Alison Schofield <alison.schofield@intel.com>

snip

> >
> > +static int gran_multiple(struct cxl_region *cxlr)
> > +{
> > +	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);
> > +	int root_decoder_gran = cxlrd->cxlsd.cxld.interleave_granularity;
> > +	int region_gran = cxlr->params.interleave_granularity;
> > +
> > +	/*
> > +	 * In regions built upon 3-way HB interleaves, the root decoder
> > +	 * granularity can be a multiple of the region granularity. The
> > +	 * multiple value is used in sorting and distance calculations.
> > +	 */
> > +	if (cxlrd->cxlsd.cxld.interleave_ways != 3 || !root_decoder_gran)
> > +		return 1;
> 
> Hi Alison,
> 
> 
> root decoder granularity is possible to be 0 here? I checked the code, the minimal value of it should be 256(CXL_DECODER_MIN_GRANULARITY), it was set in __cxl_parse_cfmws().
> 
> maybe this '!root_decoder_gran' checking is not needed?

Thanks for looking that up. I imagine I had some divide by zero concern,
which would have been wrong too.

Removed check in v2.

-- Alison

> 
> 
> Ming
> 
> [snip]
> 
>