[PATCH v5 02/27] cxl/regs: Let a BAR-owning driver own the component register block

[<mhonap@nvidia.com>]

From: Manish Honap <mhonap@nvidia.com>

cxl_map_component_regs() claims each mapped sub-block with
devm_request_mem_region(). A driver that already requested the whole
component register BAR, such as vfio-cxl, would then collide with that
claim and fail to map the HDM decoder and RAS blocks.

Add cxl_reg_map_add_owned_resource() so such a driver records the
resource it already owns on the register map, and skip the sub-block
request when the block falls within an owned resource.

Assisted-by: LLM
Signed-off-by: Manish Honap <mhonap@nvidia.com>
---
 drivers/cxl/core/regs.c | 17 +++++++++++++++--
 include/cxl/cxl.h       |  2 ++
 include/cxl/pci.h       |  3 +++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
index d79550dbb484..58a7c5cafb45 100644
--- a/drivers/cxl/core/regs.c
+++ b/drivers/cxl/core/regs.c
@@ -216,6 +216,13 @@ void __iomem *devm_cxl_iomap_block(struct device *dev, resource_size_t addr,
 }
 EXPORT_SYMBOL_NS_GPL(devm_cxl_iomap_block, "CXL");
 
+void cxl_reg_map_add_owned_resource(struct cxl_register_map *map,
+				    struct resource *res)
+{
+	map->owned = res;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_reg_map_add_owned_resource, "CXL");
+
 int cxl_map_component_regs(const struct cxl_register_map *map,
 			   struct cxl_component_regs *regs,
 			   unsigned long map_mask)
@@ -234,6 +241,7 @@ int cxl_map_component_regs(const struct cxl_register_map *map,
 		struct mapinfo *mi = &mapinfo[i];
 		resource_size_t addr;
 		resource_size_t length;
+		struct resource res;
 
 		if (!mi->rmap->valid)
 			continue;
@@ -241,8 +249,13 @@ int cxl_map_component_regs(const struct cxl_register_map *map,
 			continue;
 		addr = map->resource + mi->rmap->offset;
 		length = mi->rmap->size;
-		*(mi->addr) = devm_cxl_iomap_block(host, addr, length);
-		if (!*(mi->addr))
+		res = DEFINE_RES_MEM(addr, length);
+
+		if (map->owned && resource_contains(map->owned, &res))
+			*mi->addr = devm_cxl_ioremap_block(host, addr, length);
+		else
+			*mi->addr = devm_cxl_iomap_block(host, addr, length);
+		if (!*mi->addr)
 			return -ENOMEM;
 	}
 
diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
index a02792969e0a..92314f67b702 100644
--- a/include/cxl/cxl.h
+++ b/include/cxl/cxl.h
@@ -217,6 +217,7 @@ struct cxl_pmu_reg_map {
  * @resource: physical resource base of the register block
  * @max_size: maximum mapping size to perform register search
  * @reg_type: see enum cxl_regloc_type
+ * @owned: driver-owned resource whose sub-blocks are mapped without re-requesting
  * @component_map: cxl_reg_map for component registers
  * @device_map: cxl_reg_maps for device registers
  * @pmu_map: cxl_reg_maps for CXL Performance Monitoring Units
@@ -227,6 +228,7 @@ struct cxl_register_map {
 	resource_size_t resource;
 	resource_size_t max_size;
 	u8 reg_type;
+	struct resource *owned;
 	union {
 		struct cxl_component_reg_map component_map;
 		struct cxl_device_reg_map device_map;
diff --git a/include/cxl/pci.h b/include/cxl/pci.h
index 3e0000015871..8e0b3bd0b3c1 100644
--- a/include/cxl/pci.h
+++ b/include/cxl/pci.h
@@ -16,7 +16,10 @@ enum cxl_regloc_type {
 
 struct cxl_register_map;
 struct pci_dev;
+struct resource;
 
 int cxl_pci_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
 		       struct cxl_register_map *map);
+void cxl_reg_map_add_owned_resource(struct cxl_register_map *map,
+				    struct resource *res);
 #endif
-- 
2.25.1