[PATCH v1 3/6] dma: fsl-qdma: workaround for ERR010812

[jiaheng.fan]

ERR010812:
Enqueue rejection occurs as a results of the lack of processing by the
consumer of the command descriptors in the status queue. This may be due
to the size of the status queue, i.e. too small, to account for the
delay in reacting to an exceeded queue threshold or other means of
determining a non-empty status queue. While increasing the status queue
size may alleviate the occurrence of enqueue rejections, it is  not a
complete solution. qDMA supports flow control (XOFF) flowing from the
status queue to the command queue(s) producing traffic. This flow
control is initiated when and enter XOFF watermark is triggered as
defined by register SQCCMR. Setting this to the recommended value in the
register description will guarantee that no enqueue rejections will ever
occur.

Signed-off-by: jiaheng.fan <jiaheng.fan at nxp.com>
---
 drivers/dma/fsl-qdma.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/dma/fsl-qdma.c b/drivers/dma/fsl-qdma.c
index 41bec13..7b9e09a 100644
--- a/drivers/dma/fsl-qdma.c
+++ b/drivers/dma/fsl-qdma.c
@@ -63,6 +63,7 @@
 #define FSL_QDMA_CQDSCR2                0xa0c
 #define FSL_QDMA_CQIER			0xa10
 #define FSL_QDMA_CQEDR			0xa14
+#define FSL_QDMA_SQCCMR			0xa20
 
 #define FSL_QDMA_SQICR_ICEN
 
@@ -76,6 +77,7 @@
 #define FSL_QDMA_BSQICR_ICST(x)		((x) << 16)
 #define FSL_QDMA_CQIER_MEIE		0x80000000
 #define FSL_QDMA_CQIER_TEIE		0x1
+#define FSL_QDMA_SQCCMR_ENTER_WM	0x200000
 
 #define FSL_QDMA_QUEUE_MAX		8
 
@@ -842,6 +844,13 @@ static int fsl_qdma_reg_init(struct fsl_qdma_engine *fsl_qdma)
 	}
 
 	/*
+	 * Workaround for erratum: ERR010812.
+	 * We must enable XOFF to avoid the enqueue rejection occurs.
+	 * Setting SQCCMR ENTER_WM to 0x20.
+	 */
+	qdma_writel(fsl_qdma, FSL_QDMA_SQCCMR_ENTER_WM,
+			      block + FSL_QDMA_SQCCMR);
+	/*
 	 * Initialize status queue registers to point to the first
 	 * command descriptor in memory.
 	 * Dequeue Pointer Address Registers
-- 
2.7.4