[RFC 02/13] cxl: introduce cxl_get_hdm_info()

[Zhi Wang <zhiw@nvidia.com>]

CXL core has the information of what CXL register groups a device has.
When initializing the device, the CXL core probes the register groups
and saves the information. The probing sequence is quite complicated.

vfio-cxl requires the HDM register information to emualte the HDM decoder
registers.

Introduce cxl_get_hdm_info() for vfio-cxl to leverage the HDM
register information in the CXL core. Thus, it doesn't need to implement
its own probing sequence.

Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 drivers/cxl/core/pci.c        | 28 ++++++++++++++++++++++++++++
 drivers/cxl/cxlpci.h          |  3 +++
 include/linux/cxl_accel_mem.h |  2 ++
 3 files changed, 33 insertions(+)

diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index a663e7566c48..7b6c2b6211b3 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -502,6 +502,34 @@ int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
 }
 EXPORT_SYMBOL_NS_GPL(cxl_hdm_decode_init, CXL);
 
+int cxl_get_hdm_info(struct cxl_dev_state *cxlds, u32 *hdm_count,
+		     u64 *hdm_reg_offset, u64 *hdm_reg_size)
+{
+	struct pci_dev *pdev = to_pci_dev(cxlds->dev);
+	int d = cxlds->cxl_dvsec;
+	u16 cap;
+	int rc;
+
+	if (!cxlds->reg_map.component_map.hdm_decoder.valid) {
+		*hdm_reg_offset = *hdm_reg_size = 0;
+	} else {
+		struct cxl_component_reg_map *map =
+			&cxlds->reg_map.component_map;
+
+		*hdm_reg_offset = map->hdm_decoder.offset;
+		*hdm_reg_size = map->hdm_decoder.size;
+	}
+
+	rc = pci_read_config_word(pdev,
+				  d + CXL_DVSEC_CAP_OFFSET, &cap);
+	if (rc)
+		return rc;
+
+	*hdm_count = FIELD_GET(CXL_DVSEC_HDM_COUNT_MASK, cap);
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_get_hdm_info, CXL);
+
 #define CXL_DOE_TABLE_ACCESS_REQ_CODE		0x000000ff
 #define   CXL_DOE_TABLE_ACCESS_REQ_CODE_READ	0
 #define CXL_DOE_TABLE_ACCESS_TABLE_TYPE		0x0000ff00
diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
index 4da07727ab9c..8d4458f7e45b 100644
--- a/drivers/cxl/cxlpci.h
+++ b/drivers/cxl/cxlpci.h
@@ -129,4 +129,7 @@ void read_cdat_data(struct cxl_port *port);
 void cxl_cor_error_detected(struct pci_dev *pdev);
 pci_ers_result_t cxl_error_detected(struct pci_dev *pdev,
 				    pci_channel_state_t state);
+
+int cxl_get_hdm_info(struct cxl_dev_state *cxlds, u32 *hdm_count,
+		     u64 *hdm_reg_offset, u64 *hdm_reg_size);
 #endif /* __CXL_PCI_H__ */
diff --git a/include/linux/cxl_accel_mem.h b/include/linux/cxl_accel_mem.h
index 5d715eea6e91..db4182fc1936 100644
--- a/include/linux/cxl_accel_mem.h
+++ b/include/linux/cxl_accel_mem.h
@@ -55,4 +55,6 @@ struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
 int cxl_region_detach(struct cxl_endpoint_decoder *cxled);
 int cxl_accel_get_region_params(struct cxl_region *region,
 				resource_size_t *start, resource_size_t *end);
+int cxl_get_hdm_info(struct cxl_dev_state *cxlds, u32 *hdm_count,
+		     u64 *hdm_reg_offset, u64 *hdm_reg_size);
 #endif
-- 
2.34.1