[PATCH v3 0/2] pmdomain: imx: build the SCU power domain driver as a module

[PATCH v3 0/2] pmdomain: imx: build the SCU power domain driver as a module

[Zhipeng.wang_1]

From: Zhipeng Wang <zhipeng.wang_1@nxp.com>

This series makes the i.MX SCU power domain driver buildable as a
loadable module, which is required for Android devices using the
Generic Kernel Image (GKI) where SoC-specific drivers must be modules.

Patch 1 exports of_stdout (which the driver references to find the
console's power domain) from the OF core with EXPORT_SYMBOL_GPL().

Patch 2 converts CONFIG_IMX_SCU_PD from bool to tristate and adds
MODULE_DEVICE_TABLE() for autoloading. subsys_initcall() is used so
that when built-in the provider probes before its consumers (e.g. the
SCU clock driver at device_initcall level), fixing existing "failed to
attached the power domain" warnings. No module_exit() is provided
since the provider cannot be safely removed at runtime.

Because of the cross-subsystem dependency (patch 1 touches drivers/of,
patch 2 touches drivers/pmdomain), I would suggest taking the whole
series through one tree.

Changes in v3:
- Use subsys_initcall() instead of module_init() to fix probe ordering
  between the power domain provider and the SCU clock consumer when
  both are built-in. (Sashiko bot)

Changes in v2:
- Drop module_platform_driver() which provides module_exit() and could
  lead to use-after-free on module unload. Use module_init() only, so
  the module cannot be unloaded. (Sashiko bot)

Zhipeng Wang (2):
  of: export of_stdout symbol
  pmdomain: imx: scu-pd: allow building as a module

 drivers/of/base.c             | 1 +
 drivers/pmdomain/imx/Kconfig  | 2 +-
 drivers/pmdomain/imx/scu-pd.c | 8 +++++++-
 3 files changed, 9 insertions(+), 2 deletions(-)

-- 
2.34.1

[PATCH v3 1/2] of: export of_stdout symbol

[Zhipeng.wang_1]

From: Zhipeng Wang <zhipeng.wang_1@nxp.com>

of_stdout is declared extern in include/linux/of.h alongside of_root
and of_chosen, but unlike those two it is not exported, preventing
modules from referencing it.

Export it with EXPORT_SYMBOL_GPL() so drivers that need the stdout
device node can be built as modules.

Signed-off-by: Zhipeng Wang <zhipeng.wang_1@nxp.com>
---
 drivers/of/base.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 6e7a42dedad3..a25c95800719 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -39,6 +39,7 @@ struct device_node *of_chosen;
 EXPORT_SYMBOL(of_chosen);
 struct device_node *of_aliases;
 struct device_node *of_stdout;
+EXPORT_SYMBOL_GPL(of_stdout);
 static const char *of_stdout_options;
 
 struct kset *of_kset;
-- 
2.34.1

[PATCH v3 2/2] pmdomain: imx: scu-pd: allow building as a module

[Zhipeng.wang_1]

From: Zhipeng Wang <zhipeng.wang_1@nxp.com>

Convert CONFIG_IMX_SCU_PD from bool to tristate to allow building as a
loadable module. This is needed on Android devices using the Generic
Kernel Image (GKI), where SoC-specific drivers must be built as modules
rather than built into the core kernel image.

For i.MX8Q devices running Android with a GKI kernel, the SCU power
domain driver must be loadable. Without tristate support, power domains
cannot be properly initialized, preventing these systems from
functioning under GKI.

Use subsys_initcall() so that when built-in the power domain provider
probes before its consumers (e.g. the SCU clock driver at
device_initcall level), fixing "failed to attached the power domain"
warnings at boot. When built as a module, subsys_initcall() is
equivalent to module_init(). No module_exit() is provided because the
SCU power domain provider is a system-level resource that cannot be
safely removed at runtime.

Add MODULE_DEVICE_TABLE() for OF-based module autoloading.

Signed-off-by: Zhipeng Wang <zhipeng.wang_1@nxp.com>
---
 drivers/pmdomain/imx/Kconfig  | 2 +-
 drivers/pmdomain/imx/scu-pd.c | 8 +++++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/pmdomain/imx/Kconfig b/drivers/pmdomain/imx/Kconfig
index 00203615c65e..472e9dec6bd4 100644
--- a/drivers/pmdomain/imx/Kconfig
+++ b/drivers/pmdomain/imx/Kconfig
@@ -21,7 +21,7 @@ config IMX9_BLK_CTRL
 	depends on PM_GENERIC_DOMAINS
 
 config IMX_SCU_PD
-	bool "IMX SCU Power Domain driver"
+	tristate "IMX SCU Power Domain driver"
 	depends on IMX_SCU
 	help
 	  The System Controller Firmware (SCFW) based power domain driver.
diff --git a/drivers/pmdomain/imx/scu-pd.c b/drivers/pmdomain/imx/scu-pd.c
index 3ec33667a308..e3f9e741daf7 100644
--- a/drivers/pmdomain/imx/scu-pd.c
+++ b/drivers/pmdomain/imx/scu-pd.c
@@ -531,6 +531,7 @@ static const struct of_device_id imx_sc_pd_match[] = {
 	{ .compatible = "fsl,scu-pd", &imx8qxp_scu_pd},
 	{ /* sentinel */ }
 };
+MODULE_DEVICE_TABLE(of, imx_sc_pd_match);
 
 static struct platform_driver imx_sc_pd_driver = {
 	.driver = {
@@ -540,7 +541,12 @@ static struct platform_driver imx_sc_pd_driver = {
 	},
 	.probe = imx_sc_pd_probe,
 };
-builtin_platform_driver(imx_sc_pd_driver);
+
+static int __init imx_sc_pd_driver_init(void)
+{
+	return platform_driver_register(&imx_sc_pd_driver);
+}
+subsys_initcall(imx_sc_pd_driver_init);
 
 MODULE_AUTHOR("Dong Aisheng <aisheng.dong@nxp.com>");
 MODULE_DESCRIPTION("IMX SCU Power Domain driver");
-- 
2.34.1

Re: [PATCH v3 2/2] pmdomain: imx: scu-pd: allow building as a module

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Building the SCU PM domain driver as a module breaks power domain attachment for SCU clocks due to unhandled deferred probing.
--

--- Patch [2]: [PATCH v3 2/2] pmdomain: imx: scu-pd: allow building as a module ---
commit 8b0026aca4b6a877c269d6333189db725f3c6d76
Author: Zhipeng Wang <zhipeng.wang_1@nxp.com>

pmdomain: imx: scu-pd: allow building as a module

This commit converts the IMX_SCU_PD config from bool to tristate to allow
building the SCU power domain driver as a loadable module, which is
required for Android GKI kernels.

> diff --git a/drivers/pmdomain/imx/Kconfig b/drivers/pmdomain/imx/Kconfig
> index 00203615c65e9..472e9dec6bd4e 100644
> --- a/drivers/pmdomain/imx/Kconfig
> +++ b/drivers/pmdomain/imx/Kconfig
> @@ -21,7 +21,7 @@ config IMX9_BLK_CTRL
>  	depends on PM_GENERIC_DOMAINS
>  
>  config IMX_SCU_PD
> -	bool "IMX SCU Power Domain driver"
> +	tristate "IMX SCU Power Domain driver"

[Severity: High]
Does building the power domain driver as a module break power domain
attachment for SCU clocks?

If IMX_SCU_PD is built as a module, there are no explicit symbol dependencies
or softdeps between the SCU clock driver and the PD provider, meaning the
clock driver might be loaded first.

Looking at the consumer side in drivers/clk/imx/clk-scu.c:

imx_clk_scu_alloc_dev() {
    ...
    ret = imx_clk_scu_attach_pd(&pdev->dev, rsrc_id);
    if (ret)
        pr_warn("%s: failed to attached the power domain %d\n",
            name, ret);

    ret = platform_device_add(pdev);
    ...
}

Since the consumer ignores the return value from the attachment attempt, an
error like -ENOENT (when the provider is not registered yet) will not
trigger a deferred probe. Furthermore, because these software-created clock
devices lack an of_node, the device core's standard deferred probing
mechanisms cannot retry the attachment later.

Will this leave the SCU clocks permanently registered without their power
domains attached, potentially causing hardware malfunctions or continuous
power waste?

>  	depends on IMX_SCU
>  	help
>  	  The System Controller Firmware (SCFW) based power domain driver.

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260722071512.3494011-1-Zhipeng.wang_1@oss.nxp.com?part=2