linux-kernel - Re: [PATCH v2 04/15] cxl/region: Calculate endpoint's region position during init

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Message-ID: <0279dabe-1c2f-46b2-a5c3-9a712a2c7311@intel.com>
Date: Thu, 20 Feb 2025 14:56:41 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Robert Richter <rrichter@....com>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Dan Williams <dan.j.williams@...el.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Davidlohr Bueso <dave@...olabs.net>
Cc: linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
 Gregory Price <gourry@...rry.net>,
 "Fabio M. De Francesco" <fabio.m.de.francesco@...ux.intel.com>,
 Terry Bowman <terry.bowman@....com>
Subject: Re: [PATCH v2 04/15] cxl/region: Calculate endpoint's region position
 during init



On 2/18/25 6:23 AM, Robert Richter wrote:
> The calculation of an endpoint's position in a region traverses all
> ports up to the root port and determines the corresponding decoders
> for that particular address range. For address translation the HPA
> range must be recalculated between ports. In order to prepare the
> implementation of address translation, move code to
> cxl_endpoint_decoder_initialize() and reuse the existing iterator
> there.
> 
> Signed-off-by: Robert Richter <rrichter@....com>
> ---
>  drivers/cxl/core/region.c | 25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index ad4a6ce37216..6f106bfa115f 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1903,7 +1903,6 @@ static int cxl_region_sort_targets(struct cxl_region *cxlr)
>  	for (i = 0; i < p->nr_targets; i++) {
>  		struct cxl_endpoint_decoder *cxled = p->targets[i];
>  
> -		cxled->pos = cxl_calc_interleave_pos(cxled);
>  		/*
>  		 * Record that sorting failed, but still continue to calc
>  		 * cxled->pos so that follow-on code paths can reliably

Do the comments need to be updated here with the deletion of that line above?

DJ

> @@ -3264,10 +3263,22 @@ static int cxl_endpoint_decoder_initialize(struct cxl_endpoint_decoder *cxled)
>  	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
>  	struct cxl_port *iter = cxled_to_port(cxled);
>  	struct cxl_decoder *root, *cxld = &cxled->cxld;
> -	struct range *hpa = &cxld->hpa_range;
> +	struct range hpa = cxld->hpa_range;
> +	struct cxl_interleave_context ctx;
> +	int rc;
>  
> -	while (iter && !is_cxl_root(iter))
> -		iter = to_cxl_port(iter->dev.parent);
> +	ctx = (struct cxl_interleave_context) {
> +		.hpa_range = &hpa,
> +	};
> +
> +	while (iter && !is_cxl_root(iter)) {
> +		/* Convert interleave settings to next port upstream. */
> +		rc = cxl_port_calc_interleave(iter, &ctx);
> +		if (rc < 0)
> +			return rc;
> +
> +		iter = parent_port_of(iter);
> +	}
>  
>  	if (!iter)
>  		return -ENXIO;
> @@ -3281,7 +3292,13 @@ static int cxl_endpoint_decoder_initialize(struct cxl_endpoint_decoder *cxled)
>  		return -ENXIO;
>  	}
>  
> +	dev_dbg(cxld->dev.parent,
> +		"%s:%s: range:%#llx-%#llx pos:%d\n",
> +		dev_name(&cxled->cxld.dev), dev_name(&cxld->dev),
> +		hpa.start, hpa.end, ctx.pos);
> +
>  	cxled->cxlrd = to_cxl_root_decoder(&root->dev);
> +	cxled->pos = ctx.pos;
>  
>  	return 0;
>  }