MIPS: lantiq: dma: reset correct number of channel

Different SoCs have a different number of channels, e.g .:
* amazon-se has 10 channels,
* danube+ar9 have 20 channels,
* vr9 has 28 channels,
* ar10 has 24 channels.

We can read the ID register and, depending on the reported
number of channels, reset the appropriate number of channels.
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/mips/lantiq/xway/dma.c

@@ -31,6 +31,7 @@
 #define LTQ_DMA_PCTRL		0x44
 #define LTQ_DMA_IRNEN		0xf4
 
+#define DMA_ID_CHNR		GENMASK(26, 20)	/* channel number */
 #define DMA_DESCPT		BIT(3)		/* descriptor complete irq */
 #define DMA_TX			BIT(8)		/* TX channel direction */
 #define DMA_CHAN_ON		BIT(0)		/* channel on / off bit */
@@ -41,7 +42,6 @@
 #define DMA_POLL		BIT(31)		/* turn on channel polling */
 #define DMA_CLK_DIV4		BIT(6)		/* polling clock divider */
 #define DMA_2W_BURST		BIT(1)		/* 2 word burst length */
-#define DMA_MAX_CHANNEL		20		/* the soc has 20 channels */
 #define DMA_ETOP_ENDIANNESS	(0xf << 8) /* endianness swap etop channels */
 #define DMA_WEIGHT	(BIT(17) | BIT(16))	/* default channel wheight */
 
@@ -207,7 +207,7 @@ ltq_dma_init(struct platform_device *pdev)
 {
 	struct clk *clk;
 	struct resource *res;
-	unsigned id;
+	unsigned int id, nchannels;
 	int i;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
@@ -229,17 +229,18 @@ ltq_dma_init(struct platform_device *pdev)
 	ltq_dma_w32(0, LTQ_DMA_IRNEN);
 
 	/* reset/configure each channel */
-	for (i = 0; i < DMA_MAX_CHANNEL; i++) {
+	id = ltq_dma_r32(LTQ_DMA_ID);
+	nchannels = ((id & DMA_ID_CHNR) >> 20);
+	for (i = 0; i < nchannels; i++) {
 		ltq_dma_w32(i, LTQ_DMA_CS);
 		ltq_dma_w32(DMA_CHAN_RST, LTQ_DMA_CCTRL);
 		ltq_dma_w32(DMA_POLL | DMA_CLK_DIV4, LTQ_DMA_CPOLL);
 		ltq_dma_w32_mask(DMA_CHAN_ON, 0, LTQ_DMA_CCTRL);
 	}
 
-	id = ltq_dma_r32(LTQ_DMA_ID);
 	dev_info(&pdev->dev,
 		"Init done - hw rev: %X, ports: %d, channels: %d\n",
-		id & 0x1f, (id >> 16) & 0xf, id >> 20);
+		id & 0x1f, (id >> 16) & 0xf, nchannels);
 
 	return 0;
 }