PCI/ASPM: Factor out pcie_wait_for_retrain()

Factor pcie_wait_for_retrain() out from pcie_retrain_link().  No functional
change intended.

[bhelgaas: split out from
https://lore.kernel.org/r/20230502083923.34562-1-ilpo.jarvinen@linux.intel.com]
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pcie/aspm.c

@@ -193,10 +193,26 @@ static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist)
 	link->clkpm_disable = blacklist ? 1 : 0;
 }
 
+static int pcie_wait_for_retrain(struct pci_dev *pdev)
+{
+	unsigned long end_jiffies;
+	u16 reg16;
+
+	/* Wait for Link Training to be cleared by hardware */
+	end_jiffies = jiffies + LINK_RETRAIN_TIMEOUT;
+	do {
+		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &reg16);
+		if (!(reg16 & PCI_EXP_LNKSTA_LT))
+			return 0;
+		msleep(1);
+	} while (time_before(jiffies, end_jiffies));
+
+	return -ETIMEDOUT;
+}
+
 static int pcie_retrain_link(struct pcie_link_state *link)
 {
 	struct pci_dev *parent = link->pdev;
-	unsigned long end_jiffies;
 	u16 reg16;
 
 	pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &reg16);
@@ -212,17 +228,7 @@ static int pcie_retrain_link(struct pcie_link_state *link)
 		pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
 	}
 
-	/* Wait for link training end. Break out after waiting for timeout */
-	end_jiffies = jiffies + LINK_RETRAIN_TIMEOUT;
-	do {
-		pcie_capability_read_word(parent, PCI_EXP_LNKSTA, &reg16);
-		if (!(reg16 & PCI_EXP_LNKSTA_LT))
-			break;
-		msleep(1);
-	} while (time_before(jiffies, end_jiffies));
-	if (reg16 & PCI_EXP_LNKSTA_LT)
-		return -ETIMEDOUT;
-	return 0;
+	return pcie_wait_for_retrain(parent);
 }
 
 /*