[PATCH v2 04/20] cxl: Split cxl_await_range_active() from media-ready wait

[<mhonap@nvidia.com>]

From: Manish Honap <mhonap@nvidia.com>

Before accessing CXL device memory after reset/power-on, the driver
must ensure media is ready. Not every CXL device implements the CXL
Memory Device register group (many Type-2 devices do not).
cxl_await_media_ready() reads cxlds->regs.memdev. Access to the
memory device registers on a Type-2 device may result in kernel
panic.

Split the HDM DVSEC range-active poll out of cxl_await_media_ready()
into a new function, cxl_await_range_active(). Type-2 devices often
lack the CXLMDEV status register, so they need the range check
without the memdev read. cxl_await_media_ready() now calls
cxl_await_range_active() for the DVSEC poll, then reads the memory
device status as before.

Co-developed-by: Zhi Wang <zhiw@nvidia.com>
Signed-off-by: Zhi Wang <zhiw@nvidia.com>
Signed-off-by: Manish Honap <mhonap@nvidia.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
---
 drivers/cxl/core/pci.c | 35 ++++++++++++++++++++++++++++++-----
 include/cxl/cxl.h      |  3 +++
 2 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index a5147602f91f..1fbe3338a0da 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -142,16 +142,24 @@ static int cxl_dvsec_mem_range_active(struct cxl_dev_state *cxlds, int id)
 	return 0;
 }
 
-/*
- * Wait up to @media_ready_timeout for the device to report memory
- * active.
+/**
+ * cxl_await_range_active - Wait for all HDM DVSEC memory ranges to be active
+ * @cxlds: CXL device state (DVSEC and HDM count must be valid)
+ *
+ * For each HDM decoder range reported in the CXL DVSEC capability, waits for
+ * the range to report MEM INFO VALID (up to 1s per range), then MEM ACTIVE
+ * (up to media_ready_timeout seconds per range, default 60s). Used by
+ * cxl_await_media_ready() and by callers that only need range readiness
+ * without checking the memory device status register.
+ *
+ * Return: 0 if all ranges become valid and active, -ETIMEDOUT if a timeout
+ * occurs, or a negative errno from config read on failure.
  */
-int cxl_await_media_ready(struct cxl_dev_state *cxlds)
+int cxl_await_range_active(struct cxl_dev_state *cxlds)
 {
 	struct pci_dev *pdev = to_pci_dev(cxlds->dev);
 	int d = cxlds->cxl_dvsec;
 	int rc, i, hdm_count;
-	u64 md_status;
 	u16 cap;
 
 	rc = pci_read_config_word(pdev,
@@ -172,6 +180,23 @@ int cxl_await_media_ready(struct cxl_dev_state *cxlds)
 			return rc;
 	}
 
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_await_range_active, "CXL");
+
+/*
+ * Wait up to @media_ready_timeout for the device to report memory
+ * active.
+ */
+int cxl_await_media_ready(struct cxl_dev_state *cxlds)
+{
+	u64 md_status;
+	int rc;
+
+	rc = cxl_await_range_active(cxlds);
+	if (rc)
+		return rc;
+
 	md_status = readq(cxlds->regs.memdev + CXLMDEV_STATUS_OFFSET);
 	if (!CXLMDEV_READY(md_status))
 		return -EIO;
diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
index f48274673b1b..45d911735883 100644
--- a/include/cxl/cxl.h
+++ b/include/cxl/cxl.h
@@ -299,6 +299,7 @@ int cxl_find_regblock(struct pci_dev *pdev, enum cxl_regloc_type type,
 		      struct cxl_register_map *map);
 void cxl_probe_component_regs(struct device *dev, void __iomem *base,
 			      struct cxl_component_reg_map *map);
+int cxl_await_range_active(struct cxl_dev_state *cxlds);
 
 #else
 
@@ -314,6 +315,8 @@ static inline void
 cxl_probe_component_regs(struct device *dev, void __iomem *base,
 			 struct cxl_component_reg_map *map)
 { }
+static inline int cxl_await_range_active(struct cxl_dev_state *cxlds)
+{ return -EOPNOTSUPP; }
 
 #endif /* CONFIG_CXL_BUS */
 
-- 
2.25.1