diff --git a/drivers/gpu/nvgpu/common/fifo/pbdma.c b/drivers/gpu/nvgpu/common/fifo/pbdma.c
index ccc167dba..c1aecdc00 100644
--- a/drivers/gpu/nvgpu/common/fifo/pbdma.c
+++ b/drivers/gpu/nvgpu/common/fifo/pbdma.c
@@ -29,10 +29,10 @@ bool nvgpu_pbdma_find_for_runlist(struct gk20a *g,
 	struct nvgpu_fifo *f = &g->fifo;
 	bool found_pbdma_for_runlist = false;
 	u32 runlist_bit;
-	u32 id;
+	u32 id = U32_MAX;
 
 	runlist_bit = BIT32(runlist_id);
-	for (id = 0; id < f->num_pbdma; id++) {
+	for (id = 0U; id < f->num_pbdma; id++) {
 		if ((f->pbdma_map[id] & runlist_bit) != 0U) {
 			nvgpu_log_info(g, "gr info: pbdma_map[%d]=%d",
 					id, f->pbdma_map[id]);
diff --git a/drivers/gpu/nvgpu/include/nvgpu/pbdma.h b/drivers/gpu/nvgpu/include/nvgpu/pbdma.h
index 16228e489..5d3c316bf 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/pbdma.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/pbdma.h
@@ -23,10 +23,47 @@
 #ifndef NVGPU_PBDMA_COMMON_H
 #define NVGPU_PBDMA_COMMON_H
 
+/**
+ * @file
+ *
+ * Push-Buffer DMA
+ *
+ * PBDMA unit fetches pushbuffer data from memory, generates
+ * commands, called "methods", from the fetched data, executes some of the
+ * generated methods itself, and sends the remainder of the methods to engines.
+ */
 struct gk20a;
 
+/**
+ * nvgpu_pbdma_setup_sw - initialize PBDMA software context
+ *
+ * @param g	Current GPU
+ *
+ * Gets number of PBDMAs and builds a map of runlists that will be serviced
+ * by those PBDMAs. Returns non-zero value in case of failure.
+ */
 int nvgpu_pbdma_setup_sw(struct gk20a *g);
+
+/**
+ * nvgpu_pbdma_cleanup_sw - clean up PBDMA software context
+ *
+ * @param g	Current GPU
+ *
+ * Cleans up PBDMA software context and related resources.
+ */
 void nvgpu_pbdma_cleanup_sw(struct gk20a *g);
+
+/**
+ * nvgpu_pbdma_find_for_runlist - find PBDMA servicing the runlist
+ *
+ * @param g     	Current GPU
+ * @param runlist_id	Runlist identifier
+ * @param pbdma_id	Pointer to PBDMA identifier
+ *
+ * Finds the PBDMA which is servicing #runlist_id.
+ * Sets #pbdma_id to valid value and returns true in case PBDMA could be found.
+ * Sets #pbdma_id to U32_MAX and returns false in case PBDMA could not be found.
+ */
 bool nvgpu_pbdma_find_for_runlist(struct gk20a *g,
 		u32 runlist_id, u32 *pbdma_id);