[PATCH v2] power-domain: fix hang in endless loop on i.MX8

[Fabio Estevam]

Hi Anatolij,

On Mon, Feb 17, 2020 at 5:42 AM Anatolij Gustschin <agust at denx.de> wrote:
>
> 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 at 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 at denx.de>

I also had to apply the following change in order to boot a i.MX8QXP MEK board:

--- a/arch/arm/mach-imx/imx8/fdt.c
+++ b/arch/arm/mach-imx/imx8/fdt.c
@@ -280,6 +280,8 @@ int ft_system_setup(void *blob, bd_t *bd)
 {
        int ret;

+       return 0;
+
        update_fdt_with_owned_resources(blob);

        if (is_imx8qm()) {

With your patch and this change a 4.14.98 NXP kernel can boot, but not
a 4.19.35 NXP nor a mainline kernel.

Tested-by: Fabio Estevam <festevam at gmail.com>