wil6210: add HW write-back option in TX descriptor

Map BIT 9 in TX DMA DWARD 0 as HW write back option.
We must turn on this option in the last TX descriptor,
this is required for old HW compatability.
This option indicate to HW that WB is required for this descriptor.
Signed-off-by: Kirshenbaum Erez <erezk@wilocity.com>
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/wil6210/txrx.c

@@ -708,7 +708,7 @@ static int wil_tx_vring(struct wil6210_priv *wil, struct vring *vring,
 	}
 	/* for the last seg only */
 	d->dma.d0 |= BIT(DMA_CFG_DESC_TX_0_CMD_EOP_POS);
-	d->dma.d0 |= BIT(9); /* BUG: undocumented bit */
+	d->dma.d0 |= BIT(DMA_CFG_DESC_TX_0_CMD_MARK_WB_POS);
 	d->dma.d0 |= BIT(DMA_CFG_DESC_TX_0_CMD_DMA_IT_POS);
 	*_d = *d;
 

drivers/net/wireless/ath/wil6210/txrx.h

@@ -201,6 +201,10 @@ struct vring_tx_mac {
 #define DMA_CFG_DESC_TX_0_CMD_EOP_LEN 1
 #define DMA_CFG_DESC_TX_0_CMD_EOP_MSK 0x100
 
+#define DMA_CFG_DESC_TX_0_CMD_MARK_WB_POS 9
+#define DMA_CFG_DESC_TX_0_CMD_MARK_WB_LEN 1
+#define DMA_CFG_DESC_TX_0_CMD_MARK_WB_MSK 0x200
+
 #define DMA_CFG_DESC_TX_0_CMD_DMA_IT_POS 10
 #define DMA_CFG_DESC_TX_0_CMD_DMA_IT_LEN 1
 #define DMA_CFG_DESC_TX_0_CMD_DMA_IT_MSK 0x400