PM / domains: Add pd_ignore_unused to keep power domains enabled

Keep all power-domains already enabled by bootloader on, even if no
driver has claimed them. This is useful for debug and development, but
should not be needed on a platform with proper driver support.

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 20 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bc3478581f67..d4aff4086952 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2558,6 +2558,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
         pcmv=           [HW,PCMCIA] BadgePAD 4
 
+        pd_ignore_unused
+                        [PM]
+                        Keep all power-domains already enabled by bootloader on,
+                        even if no driver has claimed them. This is useful
+                        for debug and development, but should not be
+                        needed on a platform with proper driver support.
+
         pd.             [PARIDE]
                         See Documentation/blockdev/paride.txt.
 
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 6f54962aae1d..ae098a261fcd 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -705,6 +705,14 @@ static int pm_genpd_runtime_resume(struct device *dev)
         return 0;
 }
 
+static bool pd_ignore_unused;
+static int __init pd_ignore_unused_setup(char *__unused)
+{
+        pd_ignore_unused = true;
+        return 1;
+}
+__setup("pd_ignore_unused", pd_ignore_unused_setup);
+
 /**
  * pm_genpd_poweroff_unused - Power off all PM domains with no devices in use.
  */
@@ -712,6 +720,11 @@ void pm_genpd_poweroff_unused(void)
 {
         struct generic_pm_domain *genpd;
 
+        if (pd_ignore_unused) {
+                pr_warn("genpd: Not disabling unused power domains\n");
+                return;
+        }
+
         mutex_lock(&gpd_list_lock);
 
         list_for_each_entry(genpd, &gpd_list, gpd_list_node)