PM / Domains: Document flags for genpd

The current documented description of the GENPD_FLAG_* flags, are too
simplified, so let's extend them.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index 776c546d581afb4064d977e4f4f729a69ea68f0a..3b5d7280e52e19971fdd0b21e311c54d39b60f15 100644 (file)
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -17,11 +17,36 @@
 #include <linux/notifier.h>
 #include <linux/spinlock.h>
 
-/* Defines used for the flags field in the struct generic_pm_domain */
-#define GENPD_FLAG_PM_CLK       (1U << 0) /* PM domain uses PM clk */
-#define GENPD_FLAG_IRQ_SAFE     (1U << 1) /* PM domain operates in atomic */
-#define GENPD_FLAG_ALWAYS_ON    (1U << 2) /* PM domain is always powered on */
-#define GENPD_FLAG_ACTIVE_WAKEUP (1U << 3) /* Keep devices active if wakeup */
+/*
+ * Flags to control the behaviour of a genpd.
+ *
+ * These flags may be set in the struct generic_pm_domain's flags field by a
+ * genpd backend driver. The flags must be set before it calls pm_genpd_init(),
+ * which initializes a genpd.
+ *
+ * GENPD_FLAG_PM_CLK:          Instructs genpd to use the PM clk framework,
+ *                             while powering on/off attached devices.
+ *
+ * GENPD_FLAG_IRQ_SAFE:                This informs genpd that its backend callbacks,
+ *                             ->power_on|off(), doesn't sleep. Hence, these
+ *                             can be invoked from within atomic context, which
+ *                             enables genpd to power on/off the PM domain,
+ *                             even when pm_runtime_is_irq_safe() returns true,
+ *                             for any of its attached devices. Note that, a
+ *                             genpd having this flag set, requires its
+ *                             masterdomains to also have it set.
+ *
+ * GENPD_FLAG_ALWAYS_ON:       Instructs genpd to always keep the PM domain
+ *                             powered on.
+ *
+ * GENPD_FLAG_ACTIVE_WAKEUP:   Instructs genpd to keep the PM domain powered
+ *                             on, in case any of its attached devices is used
+ *                             in the wakeup path to serve system wakeups.
+ */
+#define GENPD_FLAG_PM_CLK       (1U << 0)
+#define GENPD_FLAG_IRQ_SAFE     (1U << 1)
+#define GENPD_FLAG_ALWAYS_ON    (1U << 2)
+#define GENPD_FLAG_ACTIVE_WAKEUP (1U << 3)
 
 enum gpd_status {
        GPD_STATE_ACTIVE = 0,   /* PM domain is active */