[PATCH v6 1/2] cxl/core/regs: Add rcd_regs initialization at __rcrb_to_component()

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

Add rcd_regs and its initialization at __rcrb_to_component() to cache
the cxl1.1 device link status information. Reduce access to the memory
map area where the RCRB is located by caching the cxl1.1 device
link status information.

Signed-off-by: "Kobayashi,Daisuke" <kobayashi.da-06@xxxxxxxxxxx>
---
 drivers/cxl/core/core.h |  4 +++-
 drivers/cxl/core/regs.c | 16 ++++++++++++++++
 drivers/cxl/cxl.h       |  3 +++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 3b64fb1b9ed0..66f62b5bb9f7 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -74,7 +74,9 @@ resource_size_t __rcrb_to_component(struct device *dev,
 				    struct cxl_rcrb_info *ri,
 				    enum cxl_rcrb which);
 u16 cxl_rcrb_to_aer(struct device *dev, resource_size_t rcrb);
-
+#define PCI_RCRB_CAP_LIST_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..1ad58c464488 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 +539,20 @@ 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_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_lnkcap = readl(addr + offset + PCI_EXP_LNKCAP);
+		ri->rcd_lnkctrl = readl(addr + offset + PCI_EXP_LNKCTL);
+		ri->rcd_lnkstatus = readl(addr + offset + PCI_EXP_LNKSTA);
+	}
+
 	iounmap(addr);
 	release_mem_region(rcrb, SZ_4K);
 
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 003feebab79b..808818ccc255 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -646,6 +646,9 @@ cxl_find_dport_by_dev(struct cxl_port *port, const struct device *dport_dev)
 
 struct cxl_rcrb_info {
 	resource_size_t base;
+	u16 rcd_lnkstatus;
+	u16 rcd_lnkctrl;
+	u32 rcd_lnkcap;
 	u16 aer_cap;
 };
 
-- 
2.44.0