[PATCH v8 1/2] cxl/core/regs: Add rcd_pcie_cap initialization at __rcrb_to_component()

["Kobayashi,Daisuke" <kobayashi.da-06@fujitsu.com>]

Add rcd_pcie_cap and its initialization at __rcrb_to_component() to cache
the offset of cxl1.1 device link status information. By caching it, avoid 
the walking memory map area to find the offset when output the register value.

Signed-off-by: "Kobayashi,Daisuke" <kobayashi.da-06@fujitsu.com>

---
 drivers/cxl/core/core.h |  4 ++++
 drivers/cxl/core/regs.c | 13 +++++++++++++
 drivers/cxl/cxl.h       |  1 +
 3 files changed, 18 insertions(+)

diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 3b64fb1b9ed0..42e3483b4a14 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -75,6 +75,10 @@ resource_size_t __rcrb_to_component(struct device *dev,
 				    enum cxl_rcrb which);
 u16 cxl_rcrb_to_aer(struct device *dev, resource_size_t rcrb);
 
+#define PCI_RCRB_CAP_LIST_ID_MASK	GENMASK(7, 0)
+#define PCI_RCRB_CAP_HDR_ID_MASK	GENMASK(7, 0)
+#define PCI_RCRB_CAP_HDR_NEXT_MASK	GENMASK(15, 8)
+
 extern struct rw_semaphore cxl_dpa_rwsem;
 extern struct rw_semaphore cxl_region_rwsem;
 
diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
index 372786f80955..3e64b49f74ed 100644
--- a/drivers/cxl/core/regs.c
+++ b/drivers/cxl/core/regs.c
@@ -514,6 +514,8 @@ resource_size_t __rcrb_to_component(struct device *dev, struct cxl_rcrb_info *ri
 	u32 bar0, bar1;
 	u16 cmd;
 	u32 id;
+	u16 offset;
+	u32 cap_hdr;
 
 	if (which == CXL_RCRB_UPSTREAM)
 		rcrb += SZ_4K;
@@ -537,6 +539,17 @@ resource_size_t __rcrb_to_component(struct device *dev, struct cxl_rcrb_info *ri
 	cmd = readw(addr + PCI_COMMAND);
 	bar0 = readl(addr + PCI_BASE_ADDRESS_0);
 	bar1 = readl(addr + PCI_BASE_ADDRESS_1);
+	offset = FIELD_GET(PCI_RCRB_CAP_LIST_ID_MASK, readw(addr + PCI_CAPABILITY_LIST));
+	cap_hdr = readl(addr + offset);
+	while ((FIELD_GET(PCI_RCRB_CAP_HDR_ID_MASK, cap_hdr)) != PCI_CAP_ID_EXP) {
+		offset = FIELD_GET(PCI_RCRB_CAP_HDR_NEXT_MASK, cap_hdr);
+		if (offset == 0 || offset > SZ_4K)
+			break;
+		cap_hdr = readl(addr + offset);
+	}
+	if (offset)
+		ri->rcd_pcie_cap = offset;
+
 	iounmap(addr);
 	release_mem_region(rcrb, SZ_4K);
 
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 003feebab79b..40396e2c4bae 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -646,6 +646,7 @@ cxl_find_dport_by_dev(struct cxl_port *port, const struct device *dport_dev)
 
 struct cxl_rcrb_info {
 	resource_size_t base;
+	u16 rcd_pcie_cap;
 	u16 aer_cap;
 };
 
-- 
2.44.0