msm: sps: add the checking of ZLT in case of an empty pipe

Check if a ZLT descriptor is the last pending descriptor in
the desc FIFO when determine if the desc FIFO of that pipe is
empty.

Change-Id: Ib8174953d6ad7d886f47f21e243e985b79ef41fb
Signed-off-by: Yan He <yanhe@codeaurora.org>

3 files changed, 107 insertions, 4 deletions

diff --git a/drivers/platform/msm/sps/bam.c b/drivers/platform/msm/sps/bam.c
index d24ff25ebb7e..e3b38fb9c5f8 100644
--- a/drivers/platform/msm/sps/bam.c
+++ b/drivers/platform/msm/sps/bam.c
@@ -177,6 +177,8 @@
 #define P_RST_P_SW_RST                             0x1
 
 /* P_HALTn */
+#define P_HALT_P_PIPE_EMPTY			   0x8
+#define P_HALT_P_LAST_DESC_ZLT                     0x4
 #define P_HALT_P_PROD_HALTED                       0x2
 #define P_HALT_P_HALT                              0x1
 
@@ -1271,6 +1273,58 @@ void bam_disable_pipe(void *base, u32 pipe)
 	wmb(); /* ensure pipe is disabled */
 }
 
+/*
+ * Check if the last desc is ZLT
+ */
+bool bam_pipe_check_zlt(void *base, u32 pipe)
+{
+	struct sps_bam *dev = to_sps_bam_dev(base);
+
+	if ((dev == NULL) || (&dev->base != base)) {
+		SPS_ERR(sps, "%s:Failed to get dev for base addr 0x%p\n",
+				__func__, base);
+		return false;
+	}
+
+	if (bam_read_reg_field(base, P_HALT, pipe, P_HALT_P_LAST_DESC_ZLT)) {
+		SPS_DBG(dev,
+			"sps:%s:bam=0x%p(va).pipe=%d: the last desc is ZLT.",
+			__func__, base, pipe);
+		return true;
+	}
+
+	SPS_DBG(dev,
+		"sps:%s:bam=0x%p(va).pipe=%d: the last desc is not ZLT.",
+		__func__, base, pipe);
+	return false;
+}
+
+/*
+ * Check if desc FIFO is empty
+ */
+bool bam_pipe_check_pipe_empty(void *base, u32 pipe)
+{
+	struct sps_bam *dev = to_sps_bam_dev(base);
+
+	if ((dev == NULL) || (&dev->base != base)) {
+		SPS_ERR(sps, "%s:Failed to get dev for base addr 0x%p\n",
+				__func__, base);
+		return false;
+	}
+
+	if (bam_read_reg_field(base, P_HALT, pipe, P_HALT_P_PIPE_EMPTY)) {
+		SPS_DBG(dev,
+			"sps:%s:bam=0x%p(va).pipe=%d: desc FIFO is empty.",
+			__func__, base, pipe);
+		return true;
+	}
+
+	SPS_DBG(dev,
+		"sps:%s:bam=0x%p(va).pipe=%d: desc FIFO is not empty.",
+		__func__, base, pipe);
+	return false;
+}
+
 /**
  * Initialize a BAM pipe
  */
diff --git a/drivers/platform/msm/sps/bam.h b/drivers/platform/msm/sps/bam.h
index d34a7d3e9b09..757c477ae5f4 100644
--- a/drivers/platform/msm/sps/bam.h
+++ b/drivers/platform/msm/sps/bam.h
@@ -1,4 +1,4 @@
-/* Copyright (c) 2011-2013, The Linux Foundation. All rights reserved.
+/* Copyright (c) 2011-2015, The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
@@ -422,4 +422,26 @@ void bam_pipe_timer_reset(void *base, u32 pipe);
  */
 u32 bam_pipe_timer_get_count(void *base, u32 pipe);
 
+/*
+ * bam_pipe_check_zlt - Check if the last desc is ZLT.
+ * @base:	BAM virtual address
+ * @pipe:	pipe index
+ *
+ * This function checks if the last desc in the desc FIFO is a ZLT desc.
+ *
+ * @return true if the last desc in the desc FIFO is a ZLT desc. Otherwise
+ *  return false.
+ */
+bool bam_pipe_check_zlt(void *base, u32 pipe);
+
+/*
+ * bam_pipe_check_pipe_empty - Check if desc FIFO is empty.
+ * @base:	BAM virtual address
+ * @pipe:	pipe index
+ *
+ * This function checks if the desc FIFO of this pipe is empty.
+ *
+ * @return true if desc FIFO is empty. Otherwise return false.
+ */
+bool bam_pipe_check_pipe_empty(void *base, u32 pipe);
 #endif				/* _BAM_H_ */
diff --git a/drivers/platform/msm/sps/sps_bam.c b/drivers/platform/msm/sps/sps_bam.c
index 48e2869d4959..17cd83730abe 100644
--- a/drivers/platform/msm/sps/sps_bam.c
+++ b/drivers/platform/msm/sps/sps_bam.c
@@ -2212,10 +2212,37 @@ int sps_bam_pipe_is_empty(struct sps_bam *dev, u32 pipe_index,
 
 
 	/* Determine descriptor FIFO state */
-	if (end_offset == acked_offset)
+	if (end_offset == acked_offset) {
 		*empty = true;
-	else
-		*empty = false;
+	} else {
+		if ((pipe->state & BAM_STATE_BAM2BAM) == 0) {
+			*empty = false;
+			return 0;
+		}
+		if (bam_pipe_check_zlt(&dev->base, pipe_index)) {
+			bool p_idc;
+			u32 next_write;
+
+			p_idc = bam_pipe_check_pipe_empty(&dev->base,
+								pipe_index);
+
+			next_write = acked_offset + sizeof(struct sps_iovec);
+			if (next_write >= pipe->desc_size)
+				next_write = 0;
+
+			if (next_write == end_offset) {
+				*empty = true;
+				if (!p_idc)
+					SPS_DBG3(dev,
+						"sps:BAM %pa pipe %d pipe empty checking for ZLT.\n",
+						BAM_ID(dev), pipe_index);
+			} else {
+				*empty = false;
+			}
+		} else {
+			*empty = false;
+		}
+	}
 
 	return 0;
 }