soc: renesas: rmobile-sysc: Set GENPD_FLAG_ALWAYS_ON for always-on domain

Currently the R-Mobile "always-on" PM Domain is implemented by returning
-EBUSY from the generic_pm_domain.power_off() callback, and doing
nothing in the generic_pm_domain.power_on() callback.  However, this
means the PM Domain core code is not aware of the semantics of this
special domain, leading to boot warnings like the following on
SH/R-Mobile SoCs:

    sh_cmt e6130000.timer: PM domain c5 will not be powered off

Fix this by making the always-on nature of the domain explicit instead,
by setting the GENPD_FLAG_ALWAYS_ON flag.  This removes the need for the
domain to provide power control callbacks.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/soc/renesas/rmobile-sysc.c

@@ -48,12 +48,8 @@ struct rmobile_pm_domain *to_rmobile_pd(struct generic_pm_domain *d)
 static int rmobile_pd_power_down(struct generic_pm_domain *genpd)
 {
 	struct rmobile_pm_domain *rmobile_pd = to_rmobile_pd(genpd);
-	unsigned int mask;
+	unsigned int mask = BIT(rmobile_pd->bit_shift);
 
-	if (rmobile_pd->bit_shift == ~0)
-		return -EBUSY;
-
-	mask = BIT(rmobile_pd->bit_shift);
 	if (rmobile_pd->suspend) {
 		int ret = rmobile_pd->suspend();
 
@@ -80,14 +76,10 @@ static int rmobile_pd_power_down(struct generic_pm_domain *genpd)
 
 static int __rmobile_pd_power_up(struct rmobile_pm_domain *rmobile_pd)
 {
-	unsigned int mask;
+	unsigned int mask = BIT(rmobile_pd->bit_shift);
 	unsigned int retry_count;
 	int ret = 0;
 
-	if (rmobile_pd->bit_shift == ~0)
-		return 0;
-
-	mask = BIT(rmobile_pd->bit_shift);
 	if (__raw_readl(rmobile_pd->base + PSTR) & mask)
 		return ret;
 
@@ -122,11 +114,15 @@ static void rmobile_init_pm_domain(struct rmobile_pm_domain *rmobile_pd)
 	struct dev_power_governor *gov = rmobile_pd->gov;
 
 	genpd->flags |= GENPD_FLAG_PM_CLK | GENPD_FLAG_ACTIVE_WAKEUP;
-	genpd->power_off		= rmobile_pd_power_down;
-	genpd->power_on			= rmobile_pd_power_up;
-	genpd->attach_dev		= cpg_mstp_attach_dev;
-	genpd->detach_dev		= cpg_mstp_detach_dev;
-	__rmobile_pd_power_up(rmobile_pd);
+	genpd->attach_dev = cpg_mstp_attach_dev;
+	genpd->detach_dev = cpg_mstp_detach_dev;
+
+	if (!(genpd->flags & GENPD_FLAG_ALWAYS_ON)) {
+		genpd->power_off = rmobile_pd_power_down;
+		genpd->power_on = rmobile_pd_power_up;
+		__rmobile_pd_power_up(rmobile_pd);
+	}
+
 	pm_genpd_init(genpd, gov ? : &simple_qos_governor, false);
 }
 
@@ -270,6 +266,11 @@ static void __init rmobile_setup_pm_domain(struct device_node *np,
 		break;
 
 	case PD_NORMAL:
+		if (pd->bit_shift == ~0) {
+			/* Top-level always-on domain */
+			pr_debug("PM domain %s is always-on domain\n", name);
+			pd->genpd.flags |= GENPD_FLAG_ALWAYS_ON;
+		}
 		break;
 	}