PCI: dwc: Log link speed and width if it comes up

Printing just "link up" isn't very informative for PCI Express. Even if the
link is up, bus performance can degrade to slower speeds or to narrower
width than both Root Port and its partner is capable of. In that case it
would be handy to know the link specifications as early as possible.

If the link comes up, log the link speed (PCIe generation) and width.

Link: https://lore.kernel.org/r/20220624143947.8991-2-Sergey.Semin@baikalelectronics.ruSigned-off-by: NSerge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Reviewed-by: NManivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

drivers/pci/controller/dwc/pcie-designware.c

@@ -524,20 +524,30 @@ void dw_pcie_disable_atu(struct dw_pcie *pci, int index,
 
 int dw_pcie_wait_for_link(struct dw_pcie *pci)
 {
+	u32 offset, val;
 	int retries;
 
 	/* Check if the link is up or not */
 	for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) {
-		if (dw_pcie_link_up(pci)) {
-			dev_info(pci->dev, "Link up\n");
-			return 0;
-		}
+		if (dw_pcie_link_up(pci))
+			break;
+
 		usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX);
 	}
 
-	dev_info(pci->dev, "Phy link never came up\n");
+	if (retries >= LINK_WAIT_MAX_RETRIES) {
+		dev_err(pci->dev, "Phy link never came up\n");
+		return -ETIMEDOUT;
+	}
+
+	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+	val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
 
-	return -ETIMEDOUT;
+	dev_info(pci->dev, "PCIe Gen.%u x%u link up\n",
+		 FIELD_GET(PCI_EXP_LNKSTA_CLS, val),
+		 FIELD_GET(PCI_EXP_LNKSTA_NLW, val));
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(dw_pcie_wait_for_link);