dm: pci: Adjust pci_find_and_bind_driver() to return -EPERM

The current code returns 0 even if it failed to find or bind a driver. The
caller then has to check the returned device to see if it is NULL. It is
better to return an error code in this case so that it is clear what
happened.

Adjust the code to return -EPERM, indicating that the device was not bound
because it is not needed for pre-relocation use. Add comments so that the
return value is clear.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

drivers/pci/pci-uclass.c

@@ -478,10 +478,17 @@ static bool pci_match_one_id(const struct pci_device_id *id,
  * pci_find_and_bind_driver() - Find and bind the right PCI driver
  *
  * This only looks at certain fields in the descriptor.
+ *
+ * @parent:	Parent bus
+ * @find_id:	Specification of the driver to find
+ * @bdf:	Bus/device/function addreess - see PCI_BDF()
+ * @devp:	Returns a pointer to the device created
+ * @return 0 if OK, -EPERM if the device is not needed before relocation and
+ *	   therefore was not created, other -ve value on error
  */
 static int pci_find_and_bind_driver(struct udevice *parent,
-				    struct pci_device_id *find_id, pci_dev_t bdf,
-				    struct udevice **devp)
+				    struct pci_device_id *find_id,
+				    pci_dev_t bdf, struct udevice **devp)
 {
 	struct pci_driver_entry *start, *entry;
 	const char *drv;
@@ -517,7 +524,7 @@ static int pci_find_and_bind_driver(struct udevice *parent,
 			 */
 			if (!(gd->flags & GD_FLG_RELOC) &&
 			    !(drv->flags & DM_FLAG_PRE_RELOC))
-				return 0;
+				return -EPERM;
 
 			/*
 			 * We could pass the descriptor to the driver as
@@ -545,7 +552,7 @@ static int pci_find_and_bind_driver(struct udevice *parent,
 	 * limited (ie: using Cache As RAM).
 	 */
 	if (!(gd->flags & GD_FLG_RELOC) && !bridge)
-		return 0;
+		return -EPERM;
 
 	/* Bind a generic driver so that the device can be used */
 	sprintf(name, "pci_%x:%x.%x", parent->seq, PCI_DEV(bdf),
@@ -633,17 +640,17 @@ int pci_bind_bus_devices(struct udevice *bus)
 			ret = pci_find_and_bind_driver(bus, &find_id, bdf,
 						       &dev);
 		}
-		if (ret)
+		if (ret == -EPERM)
+			continue;
+		else if (ret)
 			return ret;
 
 		/* Update the platform data */
-		if (dev) {
-			pplat = dev_get_parent_platdata(dev);
-			pplat->devfn = PCI_MASK_BUS(bdf);
-			pplat->vendor = vendor;
-			pplat->device = device;
-			pplat->class = class;
-		}
+		pplat = dev_get_parent_platdata(dev);
+		pplat->devfn = PCI_MASK_BUS(bdf);
+		pplat->vendor = vendor;
+		pplat->device = device;
+		pplat->class = class;
 	}
 
 	return 0;