OMAP: PM: implement context loss count APIs

Implement OMAP PM layer omap_pm_get_dev_context_loss_count() API by
creating similar APIs at the omap_device and omap_hwmod levels.  The
omap_hwmod level call is the layer with access to the powerdomain
core, so it is the place where the powerdomain is queried to get the
context loss count.

The new APIs return an unsigned value that can wrap as the
context-loss count grows.  However, the wrapping is not important as
the role of this function is to determine context loss by checking for
any difference in subsequent calls to this function.

Note that these APIs at each level can return zero when no context
loss is detected, or on errors.  This is to avoid returning error
codes which could potentially be mistaken for large context loss
counters.

NOTE: only works for devices which have been converted to use
      omap_device/omap_hwmod.

Longer term, we could possibly remove this API from the OMAP PM layer,
and instead directly use the omap_device level API.

Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/arch/arm/plat-omap/omap_device.c b/arch/arm/plat-omap/omap_device.c
index abe933cd8f0..57adb270767 100644
--- a/arch/arm/plat-omap/omap_device.c
+++ b/arch/arm/plat-omap/omap_device.c
@@ -280,6 +280,34 @@ static void _add_optional_clock_alias(struct omap_device *od,
 /* Public functions for use by core code */
 
 /**
+ * omap_device_get_context_loss_count - get lost context count
+ * @od: struct omap_device *
+ *
+ * Using the primary hwmod, query the context loss count for this
+ * device.
+ *
+ * Callers should consider context for this device lost any time this
+ * function returns a value different than the value the caller got
+ * the last time it called this function.
+ *
+ * If any hwmods exist for the omap_device assoiated with @pdev,
+ * return the context loss counter for that hwmod, otherwise return
+ * zero.
+ */
+u32 omap_device_get_context_loss_count(struct platform_device *pdev)
+{
+	struct omap_device *od;
+	u32 ret = 0;
+
+	od = _find_by_pdev(pdev);
+
+	if (od->hwmods_cnt)
+		ret = omap_hwmod_get_context_loss_count(od->hwmods[0]);
+
+	return ret;
+}
+
+/**
  * omap_device_count_resources - count number of struct resource entries needed
  * @od: struct omap_device *
  *