dw_dmac: Pass Channel Allocation Order from platform_data

In SPEAr Platform channels 4-7 have more Fifo depth. So we must get better
channel first. This patch introduces concept of channel allocation order in
dw_dmac. If user doesn't pass anything or 0, than normal (ascending) channel
allocation will follow, else channels will be allocated in descending order.

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/dw_dmac.c

@@ -1319,7 +1319,11 @@ static int __init dw_probe(struct platform_device *pdev)
 		dwc->chan.device = &dw->dma;
 		dwc->chan.cookie = dwc->completed = 1;
 		dwc->chan.chan_id = i;
-		list_add_tail(&dwc->chan.device_node, &dw->dma.channels);
+		if (pdata->chan_allocation_order == CHAN_ALLOCATION_ASCENDING)
+			list_add_tail(&dwc->chan.device_node,
+					&dw->dma.channels);
+		else
+			list_add(&dwc->chan.device_node, &dw->dma.channels);
 
 		dwc->ch_regs = &__dw_regs(dw)->CHAN[i];
 		spin_lock_init(&dwc->lock);

include/linux/dw_dmac.h

@@ -22,6 +22,9 @@
 struct dw_dma_platform_data {
 	unsigned int	nr_channels;
 	bool		is_private;
+#define CHAN_ALLOCATION_ASCENDING	0	/* zero to seven */
+#define CHAN_ALLOCATION_DESCENDING	1	/* seven to zero */
+	unsigned char	chan_allocation_order;
 };
 
 /**