[PATCH] soc: renesas: rcar-sysc: Make PM domain initialization more robust

[Geert Uytterhoeven]

The quirk for R-Car E3 ES1.0 added in commit 086b399965a7ee7e ("soc:
renesas: r8a77990-sysc: Add workaround for 3DG-{A,B}") makes the 3DG-A
PM domain a subdomain of the 3DG-B PM domain.  However, registering
3DG-A with its parent fails silently, as the 3DG-B PM domain hasn't been
registered yet, and such failures are never reported.

Fix this by:
  1. Splitting PM Domain initialization in two steps, so all PM domains
     are registered before any child-parent links are established,
  2. Reporting any failures in establishing child-parent relations.

Check for and report pm_genpd_init() failures, too, as that function
gained a return value in commit 7eb231c337e00735 ("PM / Domains: Convert
pm_genpd_init() to return an error code").

Fixes: 086b399965a7ee7e ("soc: renesas: r8a77990-sysc: Add workaround for 
3DG-{A,B}")
Signed-off-by: Geert Uytterhoeven <geert+rene...@glider.be>
---
 drivers/soc/renesas/rcar-sysc.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/drivers/soc/renesas/rcar-sysc.c b/drivers/soc/renesas/rcar-sysc.c
index 4db53fa38abc5cf3..99e926f68299878d 100644
--- a/drivers/soc/renesas/rcar-sysc.c
+++ b/drivers/soc/renesas/rcar-sysc.c
@@ -379,11 +379,12 @@ static int rcar_sysc_pd_power_on(struct generic_pm_domain 
*genpd)
 
 static bool has_cpg_mstp;
 
-static void __init rcar_sysc_pd_setup(struct rcar_sysc_pd *pd)
+static int __init rcar_sysc_pd_setup(struct rcar_sysc_pd *pd)
 {
        struct generic_pm_domain *genpd = &pd->genpd;
        const char *name = pd->genpd.name;
        struct dev_power_governor *gov = &simple_qos_governor;
+       int error;
 
        if (pd->flags & PD_CPU) {
                /*
@@ -436,7 +437,11 @@ static void __init rcar_sysc_pd_setup(struct rcar_sysc_pd 
*pd)
        rcar_sysc_power_up(&pd->ch);
 
 finalize:
-       pm_genpd_init(genpd, gov, false);
+       error = pm_genpd_init(genpd, gov, false);
+       if (error)
+               pr_err("Failed to init PM domain %s: %d\n", name, error);
+
+       return error;
 }
 
 static const struct of_device_id rcar_sysc_matches[] __initconst = {
@@ -560,6 +565,9 @@ static int __init rcar_sysc_pd_init(void)
        pr_debug("%pOF: syscier = 0x%08x\n", np, syscier);
        iowrite32(syscier, base + SYSCIER);
 
+       /*
+        * First, create all PM domains
+        */
        for (i = 0; i < info->num_areas; i++) {
                const struct rcar_sysc_area *area = &info->areas[i];
                struct rcar_sysc_pd *pd;
@@ -582,14 +590,29 @@ static int __init rcar_sysc_pd_init(void)
                pd->ch.isr_bit = area->isr_bit;
                pd->flags = area->flags;
 
-               rcar_sysc_pd_setup(pd);
-               if (area->parent >= 0)
-                       pm_genpd_add_subdomain(domains->domains[area->parent],
-                                              &pd->genpd);
+               error = rcar_sysc_pd_setup(pd);
+               if (error)
+                       goto out_put;
 
                domains->domains[area->isr_bit] = &pd->genpd;
        }
 
+       /*
+        * Second, link all PM domains to their parents
+        */
+       for (i = 0; i < info->num_areas; i++) {
+               const struct rcar_sysc_area *area = &info->areas[i];
+
+               if (!area->name || area->parent < 0)
+                       continue;
+
+               error = pm_genpd_add_subdomain(domains->domains[area->parent],
+                                              domains->domains[area->isr_bit]);
+               if (error)
+                       pr_warn("Failed to add PM subdomain %s to parent %u\n",
+                               area->name, area->parent);
+       }
+
        error = of_genpd_add_provider_onecell(np, &domains->onecell_data);
 
 out_put:
-- 
2.7.4