PCI: dwc: Wait for link up only if link is started

In dw_pcie_host_init() regardless of whether the link has been
started or not, the code waits for the link to come up. Even in
cases where start_link() is not defined the code ends up spinning
in a loop for 1 second. Since in some systems dw_pcie_host_init()
gets called during probe, this one second loop for each pcie
interface instance ends up extending the boot time.

Wait for the link up in only if the start_link() is defined.

Link: https://lore.kernel.org/r/20230412093425.3659088-1-ajayagarwal@google.com
Tested-by: Will McVicker <willmcvicker@google.com>
Signed-off-by: Sajid Dalvi <sdalvi@google.com>
Signed-off-by: Ajay Agarwal <ajayagarwal@google.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>

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

@@ -485,14 +485,19 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
 	if (ret)
 		goto err_remove_edma;
 
-	if (!dw_pcie_link_up(pci)) {
+	if (dw_pcie_link_up(pci)) {
+		dw_pcie_print_link_status(pci);
+	} else {
 		ret = dw_pcie_start_link(pci);
 		if (ret)
 			goto err_remove_edma;
-	}
 
-	/* Ignore errors, the link may come up later */
-	dw_pcie_wait_for_link(pci);
+		if (pci->ops && pci->ops->start_link) {
+			ret = dw_pcie_wait_for_link(pci);
+			if (ret)
+				goto err_stop_link;
+		}
+	}
 
 	bridge->sysdata = pp;
 

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

@@ -644,9 +644,20 @@ void dw_pcie_disable_atu(struct dw_pcie *pci, u32 dir, int index)
 	dw_pcie_writel_atu(pci, dir, index, PCIE_ATU_REGION_CTRL2, 0);
 }
 
-int dw_pcie_wait_for_link(struct dw_pcie *pci)
+void dw_pcie_print_link_status(struct dw_pcie *pci)
 {
 	u32 offset, val;
+
+	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+	val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
+
+	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));
+}
+
+int dw_pcie_wait_for_link(struct dw_pcie *pci)
+{
 	int retries;
 
 	/* Check if the link is up or not */
@@ -662,12 +673,7 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci)
 		return -ETIMEDOUT;
 	}
 
-	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
-	val = dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKSTA);
-
-	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));
+	dw_pcie_print_link_status(pci);
 
 	return 0;
 }

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

@@ -429,6 +429,7 @@ void dw_pcie_setup(struct dw_pcie *pci);
 void dw_pcie_iatu_detect(struct dw_pcie *pci);
 int dw_pcie_edma_detect(struct dw_pcie *pci);
 void dw_pcie_edma_remove(struct dw_pcie *pci);
+void dw_pcie_print_link_status(struct dw_pcie *pci);
 
 static inline void dw_pcie_writel_dbi(struct dw_pcie *pci, u32 reg, u32 val)
 {