cxl/port: Fix find_cxl_root() for RCDs and simplify it
The find_cxl_root() helper is used to lookup root decoders and other CXL platform topology information for a given endpoint. It turns out that for RCDs it has never worked. The result of find_cxl_root(&cxlmd->dev) is always NULL for the RCH topology case because it expects to find a cxl_port at the host-bridge. RCH topologies only have the root cxl_port object with the host-bridge as a dport. While there are no reports of this being a problem to date, by inspection region enumeration should crash as a result of this problem, and it does in a local unit test for this scenario. However, an observation that ever since: commit f17b558d ("cxl/pmem: Refactor nvdimm device registration, delete the workqueue") ...all callers of find_cxl_root() occur after the memdev connection to the port topology has been established. That means that find_cxl_root() can be simplified to a walk of the endpoint port topology to the root. Switch to that arrangement which also fixes the RCD bug. Fixes: a32320b7 ("cxl/region: Add region autodiscovery") Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Reviewed-by: Dave Jiang <dave.jiang@intel.com> Link: https://lore.kernel.org/r/168002857715.50647.344876437247313909.stgit@dwillia2-xfh.jf.intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>
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