Re: [PATCH 07/19] cxl/region: Manage decoder target_type at decoder-attach time

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Sun, 04 Jun 2023 16:32:16 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> Switch-level (mid-level) decoders between the platform root and an
> endpoint can dynamically switch modes between HDM-H and HDM-D[B]
> depending on which region they target. Use the region type to fixup each
> decoder that gets allocated to map the given region.
> 
> Note that endpoint decoders are meant to determine the region type, so
> warn if those ever need to be fixed up, but since it is possible to
> continue do so.
> 
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/cxl/core/region.c |   12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index dca94c458b8f..c7170d92f47f 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -809,6 +809,18 @@ static int cxl_rr_alloc_decoder(struct cxl_port *port, struct cxl_region *cxlr,
>  		return -EBUSY;
>  	}
>  
> +	/*
> +	 * Endpoints should already match the region type, but backstop that
> +	 * assumption with an assertion. Switch-decoders change mapping-type
> +	 * based on what is mapped when they are assigned to a region.
> +	 */
> +	dev_WARN_ONCE(&cxlr->dev,
> +		      port == cxled_to_port(cxled) &&
> +			      cxld->target_type != cxlr->type,
> +		      "%s:%s mismatch decoder type %d -> %d\n",
> +		      dev_name(&cxled_to_memdev(cxled)->dev),
> +		      dev_name(&cxld->dev), cxld->target_type, cxlr->type);
> +	cxld->target_type = cxlr->type;
>  	cxl_rr->decoder = cxld;
>  	return 0;
>  }
>