driver core: platform: Drop dev_pm_domain_detach() call

On the Renesas RZ/G3S (and other Renesas SoCs, e.g., RZ/G2{L, LC, UL}),
clocks are managed through PM domains. These PM domains, registered on
behalf of the clock controller driver, are configured with
GENPD_FLAG_PM_CLK. In most of the Renesas drivers used by RZ SoCs, the
clocks are enabled/disabled using runtime PM APIs. The power domains may
also have power_on/power_off support implemented. After the device PM
domain is powered off any CPU accesses to these domains leads to system
aborts.

During probe, devices are attached to the PM domain controlling their
clocks and power. Similarly, during removal, devices are detached from the
PM domain.

The detachment call stack is as follows:

device_driver_detach() ->
  device_release_driver_internal() ->
    __device_release_driver() ->
      device_remove() ->
        platform_remove() ->
          dev_pm_domain_detach()

During driver unbind, after the device is detached from its PM domain,
the device_unbind_cleanup() function is called, which subsequently
invokes devres_release_all(). This function handles devres resource
cleanup.

If runtime PM is enabled in driver probe via devm_pm_runtime_enable(),
the cleanup process triggers the action or reset function for disabling
runtime PM. This function is pm_runtime_disable_action(), which leads
to the following call stack of interest when called:

pm_runtime_disable_action() ->
  pm_runtime_dont_use_autosuspend() ->
    __pm_runtime_use_autosuspend() ->
      update_autosuspend() ->
        rpm_idle()

The rpm_idle() function attempts to resume the device at runtime.
However, at the point it is called, the device is no longer part of a PM
domain (which manages clocks and power states). If the driver implements
its own runtime PM APIs for specific functionalities - such as the
rzg2l_adc driver - while also relying on the power domain subsystem for
power management, rpm_idle() will invoke the driver's runtime PM API.
However, since the device is no longer part of a PM domain at this point,
the PM domain's runtime PM APIs will not be called. This leads to system
aborts on Renesas SoCs.

Another identified case is when a subsystem performs various cleanups
using device_unbind_cleanup(), calling driver-specific APIs in the
process. A known example is the thermal subsystem, which may call driver-
specific APIs to disable the thermal device. The relevant call stack in
this case is:

device_driver_detach() ->
  device_release_driver_internal() ->
    device_unbind_cleanup() ->
      devres_release_all() ->
        devm_thermal_of_zone_release() ->
          thermal_zone_device_disable() ->
            thermal_zone_device_set_mode() ->
              struct thermal_zone_device_ops::change_mode()

At the moment the driver-specific change_mode() API is called, the
device is no longer part of its PM domain. Accessing its registers
without proper power management leads to system aborts.

Drop the call to dev_pm_domain_detach() from the platform bus remove
function and rely on the newly introduced call in device_unbind_cleanup().

This ensures the same effect, but the call now occurs after all
driver-specific devres resources have been freed.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://patch.msgid.link/20250703112708.1621607-4-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index df1ec34fdf567ccb66a162415a565b889be1c375..09450349cf32364bcb3c8dd94023406442ec204d 100644 (file)
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -1396,15 +1396,13 @@ static int platform_probe(struct device *_dev)
        if (ret < 0)
                return ret;
 
-       ret = dev_pm_domain_attach(_dev, PD_FLAG_ATTACH_POWER_ON);
+       ret = dev_pm_domain_attach(_dev, PD_FLAG_ATTACH_POWER_ON |
+                                        PD_FLAG_DETACH_POWER_OFF);
        if (ret)
                goto out;
 
-       if (drv->probe) {
+       if (drv->probe)
                ret = drv->probe(dev);
-               if (ret)
-                       dev_pm_domain_detach(_dev, true);
-       }
 
 out:
        if (drv->prevent_deferred_probe && ret == -EPROBE_DEFER) {
@@ -1422,7 +1420,6 @@ static void platform_remove(struct device *_dev)
 
        if (drv->remove)
                drv->remove(dev);
-       dev_pm_domain_detach(_dev, true);
 }
 
 static void platform_shutdown(struct device *_dev)