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

From: Dave Jiang <dave.jiang@intel.com>
To: Dan Williams <dan.j.williams@intel.com>, <linux-cxl@vger.kernel.org>
Cc: <ira.weiny@intel.com>, <navneet.singh@intel.com>
Subject: Re: [PATCH 07/19] cxl/region: Manage decoder target_type at decoder-attach time
Date: Tue, 13 Jun 2023 15:42:44 -0700	[thread overview]
Message-ID: <dbfde134-149d-0150-29de-39b4d4570e01@intel.com> (raw)
In-Reply-To: <168592153599.1948938.3754212703217628741.stgit@dwillia2-xfh.jf.intel.com>


On 6/4/23 16:32, Dan Williams 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: Dave Jiang <dave.jiang@intel.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;
>   }
>