ARM: at91: pm: fix imbalanced reference counter for ethernet devices

The of_find_device_by_node() function is returning a struct platform_device
object with the embedded struct device member's reference counter
incremented. This needs to be dropped when done with the platform device
returned by of_find_device_by_node().

at91_pm_eth_quirk_is_valid() calls of_find_device_by_node() on
suspend and resume path. On suspend it calls of_find_device_by_node() and
on resume and failure paths it drops the counter of
struct platform_device::dev.

In case ethernet device may not wakeup there is a put_device() on
at91_pm_eth_quirk_is_valid() which is wrong as it colides with
put_device() on resume path leading to the reference counter of struct
device embedded in struct platform_device to be messed, stack trace to be
displayed (after 5 consecutive suspend/resume cycles) and execution to
hang.

Along with this the error path of at91_pm_config_quirks() had been also
adapted to decrement propertly the reference counter of struct device
embedded in struct platform_device.

Fixes: b7fc72c ("ARM: at91: pm: add quirks for pm")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20230518062511.2988500-1-claudiu.beznea@microchip.com

Author: claudiubeznea

arch/arm/mach-at91/pm.c

@@ -334,16 +334,14 @@ static bool at91_pm_eth_quirk_is_valid(struct at91_pm_quirk_eth *eth)
 		pdev = of_find_device_by_node(eth->np);
 		if (!pdev)
 			return false;
+		/* put_device(eth->dev) is called at the end of suspend. */
 		eth->dev = &pdev->dev;
 	}
 
 	/* No quirks if device isn't a wakeup source. */
-	if (!device_may_wakeup(eth->dev)) {
-		put_device(eth->dev);
+	if (!device_may_wakeup(eth->dev))
 		return false;
-	}
 
-	/* put_device(eth->dev) is called at the end of suspend. */
 	return true;
 }
 
@@ -439,14 +437,14 @@ static int at91_pm_config_quirks(bool suspend)
 				pr_err("AT91: PM: failed to enable %s clocks\n",
 				       j == AT91_PM_G_ETH ? "geth" : "eth");
 			}
-		} else {
-			/*
-			 * Release the reference to eth->dev taken in
-			 * at91_pm_eth_quirk_is_valid().
-			 */
-			put_device(eth->dev);
-			eth->dev = NULL;
 		}
+
+		/*
+		 * Release the reference to eth->dev taken in
+		 * at91_pm_eth_quirk_is_valid().
+		 */
+		put_device(eth->dev);
+		eth->dev = NULL;
 	}
 
 	return ret;