power-domain: fix hang in endless loop on i.MX8

Currently when booting the kernel on i.MX8 U-Boot hangs in an
endless loop when switching off dma, connectivity or lsio power
domains during device removal. It hapens first when removing
gpio0 (gpio@5d080000) device, here its power domain device
'lsio_gpio0' is obtained for switching off power. Since the
obtained 'lsio_gpio0' device is removed afterwards, its power
domain is also switched off and here the parent power domain
device 'lsio_power_domain' is optained for switching off the
power. Thereafter, when the obtained 'lsio_power_domain' is
removed, device_remove() removes its first child 'lsio_gpio0'.
During this child removal the 'lsio_power_domain' device is
obtained again for switching and when removing it later,
the same child removal is repeated, so we are stuck in an
endless loop. Below is a snippet from dm tree on i.MX8QXP
for better illustration of the DM devices relationship:

 Class     Index  Probed  Driver                Name
-----------------------------------------------------------
 root          0  [ + ]   root_driver           root_driver
...
 simple_bus    0  [ + ]   generic_simple_bus    |-- imx8qx-pm
 power_doma    0  [ + ]   imx8_power_domain     |   |-- lsio_power_domain
 power_doma    1  [ + ]   imx8_power_domain     |   |   |-- lsio_gpio0
 power_doma    2  [ + ]   imx8_power_domain     |   |   |-- lsio_gpio1

Do not remove a power domain device if it is a parent of the
currently controlled device.

Fixes: 52edfed65de9 ("dm: core: device: switch off power domain after device removal")
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Reported-by: Oliver Graute <oliver.graute@gmail.com>
Reported-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Tested-by: Fabio Estevam <festevam@gmail.com>

diff --git a/drivers/power/domain/power-domain-uclass.c b/drivers/power/domain/power-domain-uclass.c
index d9c623b56e772cb9fea84519aebe1faaec02d510..2b7a1cb8fe3becceaae0d251ea85984166fdc238 100644 (file)
--- a/drivers/power/domain/power-domain-uclass.c
+++ b/drivers/power/domain/power-domain-uclass.c
@@ -127,6 +127,17 @@ static int dev_power_domain_ctrl(struct udevice *dev, bool on)
                        ret = power_domain_off(&pd);
        }
 
+       /*
+        * For platforms with parent and child power-domain devices
+        * we may not run device_remove() on the power-domain parent
+        * because it will result in removing its children and switching
+        * off their power-domain parent. So we will get here again and
+        * again and will be stuck in an endless loop.
+        */
+       if (!on && dev_get_parent(dev) == pd.dev &&
+           device_get_uclass_id(dev) == UCLASS_POWER_DOMAIN)
+               return ret;
+
        /*
         * power_domain_get() bound the device, thus
         * we must remove it again to prevent unbinding