dma: mmp-tdma: refine dma disable and dma-pos update

Below are the refinements.
1. Set DMA abort bit when disabling dma channel. This will clear
the remaining data in dma FIFO, to fix channel-swap issue.
2. Read DMA HW pointer when updating DMA status. Previously dma
position is calculated by adding one period size in dma interrupt.
This is inaccurate/insufficient for some high-quality audio APP.
Since interrupt bottom half handler has variable schedule delay,
it causes big error when calculating sample delay. Read the actual
HW pointer and feedback can improve the accuracy.
3. Do some minor code clean.

Signed-off-by: Qiao Zhou <zhouqiao@marvell.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/mmp_tdma.c

@@ -110,7 +110,7 @@ struct mmp_tdma_chan {
 	struct tasklet_struct		tasklet;
 
 	struct mmp_tdma_desc		*desc_arr;
-	phys_addr_t			desc_arr_phys;
+	dma_addr_t			desc_arr_phys;
 	int				desc_num;
 	enum dma_transfer_direction	dir;
 	dma_addr_t			dev_addr;
@@ -166,9 +166,12 @@ static void mmp_tdma_enable_chan(struct mmp_tdma_chan *tdmac)
 static int mmp_tdma_disable_chan(struct dma_chan *chan)
 {
 	struct mmp_tdma_chan *tdmac = to_mmp_tdma_chan(chan);
+	u32 tdcr;
 
-	writel(readl(tdmac->reg_base + TDCR) & ~TDCR_CHANEN,
-					tdmac->reg_base + TDCR);
+	tdcr = readl(tdmac->reg_base + TDCR);
+	tdcr |= TDCR_ABR;
+	tdcr &= ~TDCR_CHANEN;
+	writel(tdcr, tdmac->reg_base + TDCR);
 
 	tdmac->status = DMA_COMPLETE;
 
@@ -296,12 +299,27 @@ static int mmp_tdma_clear_chan_irq(struct mmp_tdma_chan *tdmac)
 	return -EAGAIN;
 }
 
+static size_t mmp_tdma_get_pos(struct mmp_tdma_chan *tdmac)
+{
+	size_t reg;
+
+	if (tdmac->idx == 0) {
+		reg = __raw_readl(tdmac->reg_base + TDSAR);
+		reg -= tdmac->desc_arr[0].src_addr;
+	} else if (tdmac->idx == 1) {
+		reg = __raw_readl(tdmac->reg_base + TDDAR);
+		reg -= tdmac->desc_arr[0].dst_addr;
+	} else
+		return -EINVAL;
+
+	return reg;
+}
+
 static irqreturn_t mmp_tdma_chan_handler(int irq, void *dev_id)
 {
 	struct mmp_tdma_chan *tdmac = dev_id;
 
 	if (mmp_tdma_clear_chan_irq(tdmac) == 0) {
-		tdmac->pos = (tdmac->pos + tdmac->period_len) % tdmac->buf_len;
 		tasklet_schedule(&tdmac->tasklet);
 		return IRQ_HANDLED;
 	} else
@@ -343,7 +361,7 @@ static void mmp_tdma_free_descriptor(struct mmp_tdma_chan *tdmac)
 	int size = tdmac->desc_num * sizeof(struct mmp_tdma_desc);
 
 	gpool = tdmac->pool;
-	if (tdmac->desc_arr)
+	if (gpool && tdmac->desc_arr)
 		gen_pool_free(gpool, (unsigned long)tdmac->desc_arr,
 				size);
 	tdmac->desc_arr = NULL;
@@ -499,6 +517,7 @@ static enum dma_status mmp_tdma_tx_status(struct dma_chan *chan,
 {
 	struct mmp_tdma_chan *tdmac = to_mmp_tdma_chan(chan);
 
+	tdmac->pos = mmp_tdma_get_pos(tdmac);
 	dma_set_tx_state(txstate, chan->completed_cookie, chan->cookie,
 			 tdmac->buf_len - tdmac->pos);
 
@@ -610,7 +629,7 @@ static int mmp_tdma_probe(struct platform_device *pdev)
 	int i, ret;
 	int irq = 0, irq_num = 0;
 	int chan_num = TDMA_CHANNEL_NUM;
-	struct gen_pool *pool;
+	struct gen_pool *pool = NULL;
 
 	of_id = of_match_device(mmp_tdma_dt_ids, &pdev->dev);
 	if (of_id)