MLK-23671-01 soc: imx: Add the rpm always on flag if necessary

Some power domain need to be runtime always on to keep
the peripherals's weekup ability, for such power domain,
add the 'GENPD_FLAG_RPM_ALWAYS_ON' flag.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Anson Huang <Anson.Huang@nxp.com>

Documentation/devicetree/bindings/power/fsl,imx8m-genpd.txt

@@ -20,6 +20,7 @@ Optional properties:
  - parent-domains: the phandle to the parent power domain
  - active-wakeup: keep the PM domain powered in case the attached device wakeup
    is enabled.
+ - rpm-always-on: keep the PM domain powered except for system suspend.
 
 example:
 	vpu_g1_pd: vpug1-pd {

drivers/soc/imx/imx8m_pm_domains.c

@@ -181,8 +181,10 @@ static int imx8m_pm_domain_probe(struct platform_device *pdev)
 	domain->pd.power_on = imx8m_pd_power_on;
 	if (of_property_read_bool(np, "active-wakeup"))
 		domain->pd.flags |= GENPD_FLAG_ACTIVE_WAKEUP;
+	if (of_property_read_bool(np, "rpm-always-on"))
+		domain->pd.flags |= GENPD_FLAG_RPM_ALWAYS_ON;
 
-	pm_genpd_init(&domain->pd, NULL, true);
+	pm_genpd_init(&domain->pd, NULL, !(domain->pd.flags & GENPD_FLAG_RPM_ALWAYS_ON));
 
 	ret = of_genpd_add_provider_simple(np, &domain->pd);
 	if (ret) {