diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index 9c41a4e..1072c45 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -192,6 +192,7 @@
  * @iomem: remapped I/O memory base
  * @n_channels: number of available channels
  * @channels: array of DMAC channels
+ * @channels_mask: bitfield of which DMA channels are managed by this driver
  * @modules: bitmask of client modules in use
  */
 struct rcar_dmac {
@@ -202,6 +203,7 @@
 
 	unsigned int n_channels;
 	struct rcar_dmac_chan *channels;
+	unsigned int channels_mask;
 
 	DECLARE_BITMAP(modules, 256);
 };
@@ -438,7 +440,7 @@
 	u16 dmaor;
 
 	/* Clear all channels and enable the DMAC globally. */
-	rcar_dmac_write(dmac, RCAR_DMACHCLR, GENMASK(dmac->n_channels - 1, 0));
+	rcar_dmac_write(dmac, RCAR_DMACHCLR, dmac->channels_mask);
 	rcar_dmac_write(dmac, RCAR_DMAOR,
 			RCAR_DMAOR_PRI_FIXED | RCAR_DMAOR_DME);
 
@@ -814,6 +816,9 @@
 	for (i = 0; i < dmac->n_channels; ++i) {
 		struct rcar_dmac_chan *chan = &dmac->channels[i];
 
+		if (!(dmac->channels_mask & BIT(i)))
+			continue;
+
 		/* Stop and reinitialize the channel. */
 		spin_lock_irq(&chan->lock);
 		rcar_dmac_chan_halt(chan);
@@ -1776,6 +1781,8 @@
 	return 0;
 }
 
+#define RCAR_DMAC_MAX_CHANNELS	32
+
 static int rcar_dmac_parse_of(struct device *dev, struct rcar_dmac *dmac)
 {
 	struct device_node *np = dev->of_node;
@@ -1787,12 +1794,16 @@
 		return ret;
 	}
 
-	if (dmac->n_channels <= 0 || dmac->n_channels >= 100) {
+	/* The hardware and driver don't support more than 32 bits in CHCLR */
+	if (dmac->n_channels <= 0 ||
+	    dmac->n_channels >= RCAR_DMAC_MAX_CHANNELS) {
 		dev_err(dev, "invalid number of channels %u\n",
 			dmac->n_channels);
 		return -EINVAL;
 	}
 
+	dmac->channels_mask = GENMASK(dmac->n_channels - 1, 0);
+
 	return 0;
 }
 
@@ -1802,7 +1813,6 @@
 		DMA_SLAVE_BUSWIDTH_2_BYTES | DMA_SLAVE_BUSWIDTH_4_BYTES |
 		DMA_SLAVE_BUSWIDTH_8_BYTES | DMA_SLAVE_BUSWIDTH_16_BYTES |
 		DMA_SLAVE_BUSWIDTH_32_BYTES | DMA_SLAVE_BUSWIDTH_64_BYTES;
-	unsigned int channels_offset = 0;
 	struct dma_device *engine;
 	struct rcar_dmac *dmac;
 	struct resource *mem;
@@ -1831,10 +1841,8 @@
 	 * level we can't disable it selectively, so ignore channel 0 for now if
 	 * the device is part of an IOMMU group.
 	 */
-	if (device_iommu_mapped(&pdev->dev)) {
-		dmac->n_channels--;
-		channels_offset = 1;
-	}
+	if (device_iommu_mapped(&pdev->dev))
+		dmac->channels_mask &= ~BIT(0);
 
 	dmac->channels = devm_kcalloc(&pdev->dev, dmac->n_channels,
 				      sizeof(*dmac->channels), GFP_KERNEL);
@@ -1892,8 +1900,10 @@
 	INIT_LIST_HEAD(&engine->channels);
 
 	for (i = 0; i < dmac->n_channels; ++i) {
-		ret = rcar_dmac_chan_probe(dmac, &dmac->channels[i],
-					   i + channels_offset);
+		if (!(dmac->channels_mask & BIT(i)))
+			continue;
+
+		ret = rcar_dmac_chan_probe(dmac, &dmac->channels[i], i);
 		if (ret < 0)
 			goto error;
 	}