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

[ Upstream commit ccd4923d18d5698a5910d516646ce125b9155d47 ]

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: b7fc72c63399 ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
index 60dc56d..437dd03 100644 (file)
--- a/arch/arm/mach-at91/pm.c
+++ b/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 @@ clk_unconfigure:
                                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;