@@ -88,4 +88,6 @@ enum cxl_poison_trace_type {
CXL_POISON_TRACE_CLEAR,
};
+long cxl_pci_get_latency(struct pci_dev *pdev);
+
#endif /* __CXL_CORE_H__ */
@@ -1,5 +1,6 @@
// SPDX-License-Identifier: GPL-2.0-only
/* Copyright(c) 2021 Intel Corporation. All rights reserved. */
+#include <linux/units.h>
#include <linux/io-64-nonatomic-lo-hi.h>
#include <linux/device.h>
#include <linux/delay.h>
@@ -980,3 +981,74 @@ pci_ers_result_t cxl_error_detected(struct pci_dev *pdev,
return PCI_ERS_RESULT_NEED_RESET;
}
EXPORT_SYMBOL_NS_GPL(cxl_error_detected, CXL);
+
+extern const unsigned char pcie_link_speed[];
+
+static enum pci_bus_speed get_link_speed(struct pci_dev *pdev)
+{
+ u16 linkstat;
+ int err;
+
+ err = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &linkstat);
+ if (err)
+ return -EINVAL;
+
+ return pcie_link_speed[linkstat & PCI_EXP_LNKSTA_CLS];
+}
+
+static int pci_bus_speed_to_mbps(enum pci_bus_speed speed)
+{
+ switch (speed) {
+ case PCIE_SPEED_2_5GT:
+ return 2500;
+ case PCIE_SPEED_5_0GT:
+ return 5000;
+ case PCIE_SPEED_8_0GT:
+ return 8000;
+ case PCIE_SPEED_16_0GT:
+ return 16000;
+ case PCIE_SPEED_32_0GT:
+ return 32000;
+ case PCIE_SPEED_64_0GT:
+ return 64000;
+ default:
+ break;
+ }
+
+ return -EINVAL;
+}
+
+static int cxl_flit_size(struct pci_dev *pdev)
+{
+ if (cxl_pci_flit_256(pdev))
+ return 256;
+
+ return 68;
+}
+
+/**
+ * cxl_pci_get_latency - calculate the link latency for the PCIe link
+ * @pdev: PCI device
+ *
+ * return: calculated latency or 0 for no latency
+ *
+ * CXL Memory Device SW Guide v1.0 2.11.4 Link latency calculation
+ * Link latency = LinkPropagationLatency + FlitLatency + RetimerLatency
+ * LinkProgationLatency is negligible, so 0 will be used
+ * RetimerLatency is assumed to be negligible and 0 will be used
+ * FlitLatency = FlitSize / LinkBandwidth
+ * FlitSize is defined by spec. CXL rev3.0 4.2.1.
+ * 68B flit is used up to 32GT/s. >32GT/s, 256B flit size is used.
+ * The FlitLatency is converted to picoseconds.
+ */
+long cxl_pci_get_latency(struct pci_dev *pdev)
+{
+ long bw;
+
+ bw = pci_bus_speed_to_mbps(get_link_speed(pdev));
+ if (bw < 0)
+ return 0;
+ bw /= BITS_PER_BYTE;
+
+ return cxl_flit_size(pdev) * MEGA / bw;
+}
@@ -856,6 +856,9 @@ static struct cxl_port *__devm_cxl_add_port(struct device *host,
if (rc)
return ERR_PTR(rc);
+ if (parent_dport && dev_is_pci(uport_dev))
+ port->pci_latency = cxl_pci_get_latency(to_pci_dev(uport_dev));
+
return port;
err:
@@ -1139,6 +1142,9 @@ __devm_cxl_add_dport(struct cxl_port *port, struct device *dport_dev,
if (rc)
return ERR_PTR(rc);
+ if (dev_is_pci(dport_dev))
+ dport->link_latency = cxl_pci_get_latency(to_pci_dev(dport_dev));
+
return dport;
}
@@ -591,6 +591,7 @@ struct cxl_dax_region {
* @depth: How deep this port is relative to the root. depth 0 is the root.
* @cdat: Cached CDAT data
* @cdat_available: Should a CDAT attribute be available in sysfs
+ * @pci_latency: Upstream latency in picoseconds
*/
struct cxl_port {
struct device dev;
@@ -613,6 +614,7 @@ struct cxl_port {
size_t length;
} cdat;
bool cdat_available;
+ long pci_latency;
};
struct cxl_root_ops {
@@ -659,6 +661,7 @@ struct cxl_rcrb_info {
* @port: reference to cxl_port that contains this downstream port
* @regs: Dport parsed register blocks
* @sw_coord: access coordinates (performance) for switch from CDAT
+ * @link_latency: calculated PCIe downstream latency
*/
struct cxl_dport {
struct device *dport_dev;
@@ -669,6 +672,7 @@ struct cxl_dport {
struct cxl_port *port;
struct cxl_regs regs;
struct access_coordinate sw_coord;
+ long link_latency;
};
/**
@@ -85,6 +85,19 @@ struct cdat_entry_header {
__le16 length;
} __packed;
+/*
+ * CXL v3.0 6.2.3 Table 6-4
+ * The table indicates that if PCIe Flit Mode is set, then CXL is in 256B flits
+ * mode, otherwise it's 68B flits mode.
+ */
+static inline bool cxl_pci_flit_256(struct pci_dev *pdev)
+{
+ u16 lnksta2;
+
+ pcie_capability_read_word(pdev, PCI_EXP_LNKSTA2, &lnksta2);
+ return lnksta2 & PCI_EXP_LNKSTA2_FLIT;
+}
+
int devm_cxl_port_enumerate_dports(struct cxl_port *port);
struct cxl_dev_state;
int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,