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Message-ID: <48855612-3643-4d91-84aa-784cbc3fd593@intel.com>
Date: Wed, 19 Nov 2025 13:44:54 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Neeraj Kumar <s.neeraj@...sung.com>, linux-cxl@...r.kernel.org,
nvdimm@...ts.linux.dev, linux-kernel@...r.kernel.org, gost.dev@...sung.com
Cc: a.manzanares@...sung.com, vishak.g@...sung.com, neeraj.kernel@...il.com
Subject: Re: [PATCH V4 10/17] cxl/mem: Refactor cxl pmem region
auto-assembling
On 11/19/25 12:52 AM, Neeraj Kumar wrote:
> In 84ec985944ef3, devm_cxl_add_nvdimm() sequence was changed and called
> before devm_cxl_add_endpoint(). It's because cxl pmem region auto-assembly
> used to get called at last in cxl_endpoint_port_probe(), which requires
> cxl_nvd presence.
>
> For cxl region persistency, region creation happens during nvdimm_probe
> which need the completion of endpoint probe.
>
> In order to accommodate both cxl pmem region auto-assembly and cxl region
> persistency, refactored following
>
> 1. Re-Sequence devm_cxl_add_nvdimm() after devm_cxl_add_endpoint(). This
> will be called only after successful completion of endpoint probe.
>
> 2. Create cxl_region_discovery() which performs pmem region
> auto-assembly and remove cxl pmem region auto-assembly from
> cxl_endpoint_port_probe()
>
> 3. Register cxl_region_discovery() with devm_cxl_add_memdev() which gets
> called during cxl_pci_probe() in context of cxl_mem_probe()
>
> 4. As cxlmd->ops->probe() calls registered cxl_region_discovery(), so
> move devm_cxl_add_nvdimm() before cxlmd->ops->probe(). It gurantees
s/gurantees/guarantees/
> both the completion of endpoint probe and cxl_nvd presence before
> calling cxlmd->ops->probe().
>
> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> ---
> drivers/cxl/core/region.c | 37 +++++++++++++++++++++++++++++++++++++
> drivers/cxl/cxl.h | 5 +++++
> drivers/cxl/mem.c | 18 +++++++++---------
> drivers/cxl/pci.c | 4 +++-
> drivers/cxl/port.c | 39 +--------------------------------------
> 5 files changed, 55 insertions(+), 48 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 2cf5b29cefd2..3c868c4de4ec 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3724,6 +3724,43 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
> }
> EXPORT_SYMBOL_NS_GPL(cxl_add_to_region, "CXL");
>
> +static int discover_region(struct device *dev, void *unused)
> +{
> + struct cxl_endpoint_decoder *cxled;
> + int rc;
> +
> + if (!is_endpoint_decoder(dev))
> + return 0;
> +
> + cxled = to_cxl_endpoint_decoder(dev);
> + if ((cxled->cxld.flags & CXL_DECODER_F_ENABLE) == 0)
> + return 0;
> +
> + if (cxled->state != CXL_DECODER_STATE_AUTO)
> + return 0;
> +
> + /*
> + * Region enumeration is opportunistic, if this add-event fails,
> + * continue to the next endpoint decoder.
> + */
> + rc = cxl_add_to_region(cxled);
> + if (rc)
> + dev_dbg(dev, "failed to add to region: %#llx-%#llx\n",
> + cxled->cxld.hpa_range.start, cxled->cxld.hpa_range.end);
> +
> + return 0;
> +}
> +
> +int cxl_region_discovery(struct cxl_memdev *cxlmd)
> +{
> + struct cxl_port *port = cxlmd->endpoint;
> +
> + device_for_each_child(&port->dev, NULL, discover_region);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_region_discovery, "CXL");
> +
> u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint, u64 spa)
> {
> struct cxl_region_ref *iter;
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index ba17fa86d249..684a0d1b441a 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -904,6 +904,7 @@ struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev);
> int cxl_add_to_region(struct cxl_endpoint_decoder *cxled);
> struct cxl_dax_region *to_cxl_dax_region(struct device *dev);
> u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint, u64 spa);
> +int cxl_region_discovery(struct cxl_memdev *cxlmd);
> #else
> static inline bool is_cxl_pmem_region(struct device *dev)
> {
> @@ -926,6 +927,10 @@ static inline u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint,
> {
> return 0;
> }
> +static inline int cxl_region_discovery(struct cxl_memdev *cxlmd)
> +{
> + return 0;
> +}
> #endif
>
> void cxl_endpoint_parse_cdat(struct cxl_port *port);
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index 13d9e089ecaf..f5e3e2fca86c 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -115,15 +115,6 @@ static int cxl_mem_probe(struct device *dev)
> return -ENXIO;
> }
>
> - if (cxl_pmem_size(cxlds) && IS_ENABLED(CONFIG_CXL_PMEM)) {
> - rc = devm_cxl_add_nvdimm(parent_port, cxlmd);
> - if (rc) {
> - if (rc == -ENODEV)
> - dev_info(dev, "PMEM disabled by platform\n");
> - return rc;
> - }
> - }
> -
> if (dport->rch)
> endpoint_parent = parent_port->uport_dev;
> else
> @@ -143,6 +134,15 @@ static int cxl_mem_probe(struct device *dev)
> return rc;
> }
>
> + if (cxl_pmem_size(cxlds) && IS_ENABLED(CONFIG_CXL_PMEM)) {
> + rc = devm_cxl_add_nvdimm(parent_port, cxlmd);
> + if (rc) {
> + if (rc == -ENODEV)
> + dev_info(dev, "PMEM disabled by platform\n");
> + return rc;
> + }
> + }
> +
> if (cxlmd->ops) {
> rc = cxlmd->ops->probe(cxlmd);
> if (rc)
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index e21051d79b25..d56fdfe4b43b 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -907,6 +907,7 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> struct cxl_memdev_state *mds;
> struct cxl_dev_state *cxlds;
> struct cxl_register_map map;
> + struct cxl_memdev_ops ops;
> struct cxl_memdev *cxlmd;
> int rc, pmu_count;
> unsigned int i;
> @@ -1006,7 +1007,8 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> if (rc)
> dev_dbg(&pdev->dev, "No CXL Features discovered\n");
>
> - cxlmd = devm_cxl_add_memdev(&pdev->dev, cxlds, NULL);
> + ops.probe = cxl_region_discovery;
> + cxlmd = devm_cxl_add_memdev(&pdev->dev, cxlds, &ops);
> if (IS_ERR(cxlmd))
> return PTR_ERR(cxlmd);
>
> diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
> index d5fd0c5ae49b..ad98b2881fed 100644
> --- a/drivers/cxl/port.c
> +++ b/drivers/cxl/port.c
> @@ -31,33 +31,6 @@ static void schedule_detach(void *cxlmd)
> schedule_cxl_memdev_detach(cxlmd);
> }
>
> -static int discover_region(struct device *dev, void *unused)
> -{
> - struct cxl_endpoint_decoder *cxled;
> - int rc;
> -
> - if (!is_endpoint_decoder(dev))
> - return 0;
> -
> - cxled = to_cxl_endpoint_decoder(dev);
> - if ((cxled->cxld.flags & CXL_DECODER_F_ENABLE) == 0)
> - return 0;
> -
> - if (cxled->state != CXL_DECODER_STATE_AUTO)
> - return 0;
> -
> - /*
> - * Region enumeration is opportunistic, if this add-event fails,
> - * continue to the next endpoint decoder.
> - */
> - rc = cxl_add_to_region(cxled);
> - if (rc)
> - dev_dbg(dev, "failed to add to region: %#llx-%#llx\n",
> - cxled->cxld.hpa_range.start, cxled->cxld.hpa_range.end);
> -
> - return 0;
> -}
> -
> static int cxl_switch_port_probe(struct cxl_port *port)
> {
> /* Reset nr_dports for rebind of driver */
> @@ -83,17 +56,7 @@ static int cxl_endpoint_port_probe(struct cxl_port *port)
> if (rc)
> return rc;
>
> - rc = devm_cxl_endpoint_decoders_setup(port);
> - if (rc)
> - return rc;
> -
> - /*
> - * Now that all endpoint decoders are successfully enumerated, try to
> - * assemble regions from committed decoders
> - */
> - device_for_each_child(&port->dev, NULL, discover_region);
> -
> - return 0;
> + return devm_cxl_endpoint_decoders_setup(port);
> }
>
> static int cxl_port_probe(struct device *dev)
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