[PATCH v4 1/7] PCI: Add pci_host_common_link_train_delay() helper

PCIe r6.0, sec 6.6.1 (Conventional Reset) requires that for a Downstream
Port supporting Link speeds greater than 5.0 GT/s, software must wait a
minimum of 100 ms after Link training completes before sending any
Configuration Request.

Introduce a static inline helper pci_host_common_link_train_delay() that
checks the given max_link_speed (2 = 5.0 GT/s, 3 = 8.0 GT/s, etc.) and
calls msleep(100) only when the speed is greater than 5.0 GT/s.

This allows multiple host controller drivers to share the same mandatory
delay without duplicating the logic.

Signed-off-by: Hans Zhang <[email protected]>
---
 drivers/pci/controller/pci-host-common.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/pci/controller/pci-host-common.h b/drivers/pci/controller/pci-host-common.h
index b5075d4bd7eb..d709f7e3e11a 100644
--- a/drivers/pci/controller/pci-host-common.h
+++ b/drivers/pci/controller/pci-host-common.h
@@ -10,6 +10,9 @@
 #ifndef _PCI_HOST_COMMON_H
 #define _PCI_HOST_COMMON_H
 
+#include <linux/delay.h>
+#include "../pci.h"
+
 struct pci_ecam_ops;
 
 int pci_host_common_probe(struct platform_device *pdev);
@@ -20,4 +23,18 @@ void pci_host_common_remove(struct platform_device *pdev);
 
 struct pci_config_window *pci_host_common_ecam_create(struct device *dev,
 	struct pci_host_bridge *bridge, const struct pci_ecam_ops *ops);
+
+/**
+ * pci_host_common_link_train_delay - Wait 100 ms if link speed > 5 GT/s
+ * @max_link_speed: the maximum link speed (2 = 5.0 GT/s, 3 = 8.0 GT/s, ...)
+ *
+ * Must be called after Link training completes and before the first
+ * Configuration Request is sent.
+ */
+static inline void pci_host_common_link_train_delay(int max_link_speed)
+{
+	if (max_link_speed > 2)
+		msleep(PCIE_RESET_CONFIG_WAIT_MS);
+}
+
 #endif
-- 
2.43.0