dw_dmac: get number of channels from hardware if possible

In case the controller has the encoded parameters feature enabled the driver
will use it to get the number of channels. In the future it will be used for
the other important parameters as well.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

drivers/dma/dw_dmac.c

@@ -1379,6 +1379,10 @@ static int __devinit dw_probe(struct platform_device *pdev)
 	struct resource		*io;
 	struct dw_dma		*dw;
 	size_t			size;
+	void __iomem		*regs;
+	bool			autocfg;
+	unsigned int		dw_params;
+	unsigned int		nr_channels;
 	int			irq;
 	int			err;
 	int			i;
@@ -1395,23 +1399,32 @@ static int __devinit dw_probe(struct platform_device *pdev)
 	if (irq < 0)
 		return irq;
 
-	size = sizeof(struct dw_dma);
-	size += pdata->nr_channels * sizeof(struct dw_dma_chan);
+	regs = devm_request_and_ioremap(&pdev->dev, io);
+	if (!regs)
+		return -EBUSY;
+
+	dw_params = dma_read_byaddr(regs, DW_PARAMS);
+	autocfg = dw_params >> DW_PARAMS_EN & 0x1;
+
+	if (autocfg)
+		nr_channels = (dw_params >> DW_PARAMS_NR_CHAN & 0x7) + 1;
+	else
+		nr_channels = pdata->nr_channels;
+
+	size = sizeof(struct dw_dma) + nr_channels * sizeof(struct dw_dma_chan);
 	dw = devm_kzalloc(&pdev->dev, size, GFP_KERNEL);
 	if (!dw)
 		return -ENOMEM;
 
-	dw->regs = devm_request_and_ioremap(&pdev->dev, io);
-	if (!dw->regs)
-		return -EBUSY;
-
 	dw->clk = devm_clk_get(&pdev->dev, "hclk");
 	if (IS_ERR(dw->clk))
 		return PTR_ERR(dw->clk);
 	clk_prepare_enable(dw->clk);
 
+	dw->regs = regs;
+
 	/* Calculate all channel mask before DMA setup */
-	dw->all_chan_mask = (1 << pdata->nr_channels) - 1;
+	dw->all_chan_mask = (1 << nr_channels) - 1;
 
 	/* force dma off, just in case */
 	dw_dma_off(dw);
@@ -1429,7 +1442,7 @@ static int __devinit dw_probe(struct platform_device *pdev)
 	tasklet_init(&dw->tasklet, dw_dma_tasklet, (unsigned long)dw);
 
 	INIT_LIST_HEAD(&dw->dma.channels);
-	for (i = 0; i < pdata->nr_channels; i++) {
+	for (i = 0; i < nr_channels; i++) {
 		struct dw_dma_chan	*dwc = &dw->chan[i];
 
 		dwc->chan.device = &dw->dma;
@@ -1442,7 +1455,7 @@ static int __devinit dw_probe(struct platform_device *pdev)
 
 		/* 7 is highest priority & 0 is lowest. */
 		if (pdata->chan_priority == CHAN_PRIORITY_ASCENDING)
-			dwc->priority = pdata->nr_channels - i - 1;
+			dwc->priority = nr_channels - i - 1;
 		else
 			dwc->priority = i;
 
@@ -1483,7 +1496,7 @@ static int __devinit dw_probe(struct platform_device *pdev)
 	dma_writel(dw, CFG, DW_CFG_DMA_EN);
 
 	printk(KERN_INFO "%s: DesignWare DMA Controller, %d channels\n",
-			dev_name(&pdev->dev), pdata->nr_channels);
+			dev_name(&pdev->dev), nr_channels);
 
 	dma_async_device_register(&dw->dma);