[PATCH 3/9] dmaengine: bcm2835: Support controllers split across several nodes

[Peter Robinson <pbrobinson@gmail.com>]

Derive the index of the first channel from the register resource and
only probe the channels it covers, so a controller can be described by
several nodes. Initialise all IRQ slots, as the shared IRQ check scans
the whole array.

Existing device trees start at channel 0 and are unaffected.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
---
 drivers/dma/bcm2835-dma.c | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index 96a39eb24559f..83ad8815759e8 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -52,12 +52,14 @@ struct bcm2835_dma_cfg {
  * @zero_page: bus address of zero page (to detect transactions copying from
  *	zero page and avoid accessing memory if so)
  * @cfg: SoC specific controller properties
+ * @first_chan: hardware index of the first channel covered by @base
  */
 struct bcm2835_dmadev {
 	struct dma_device ddev;
 	void __iomem *base;
 	dma_addr_t zero_page;
 	const struct bcm2835_dma_cfg *cfg;
+	unsigned int first_chan;
 };
 
 struct bcm2835_dma_cb {
@@ -175,8 +177,8 @@ struct bcm2835_desc {
 #define BCM2835_DMA_DATA_TYPE_S128	16
 
 /* Valid only for channels 0 - 14, 15 has its own base address */
-#define BCM2835_DMA_CHAN(n)	((n) << 8) /* Base address */
-#define BCM2835_DMA_CHANIO(base, n) ((base) + BCM2835_DMA_CHAN(n))
+#define BCM2835_DMA_CHAN_SIZE	0x100
+#define BCM2835_DMA_CHAN(n)	((n) * BCM2835_DMA_CHAN_SIZE) /* Base address */
 
 /* the max dma length for different channels */
 #define MAX_DMA_LEN SZ_1G
@@ -886,7 +888,7 @@ static int bcm2835_dma_chan_init(struct bcm2835_dmadev *d, int chan_id,
 	c->vc.desc_free = bcm2835_dma_desc_free;
 	vchan_init(&c->vc, &d->ddev);
 
-	c->chan_base = BCM2835_DMA_CHANIO(d->base, chan_id);
+	c->chan_base = d->base + BCM2835_DMA_CHAN(chan_id - d->first_chan);
 	c->ch = chan_id;
 	c->irq_number = irq;
 	c->irq_flags = irq_flags;
@@ -960,6 +962,7 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
 {
 	const struct bcm2835_dma_cfg *cfg;
 	struct bcm2835_dmadev *od;
+	struct resource *res;
 	void __iomem *base;
 	int rc;
 	int i, j;
@@ -967,6 +970,7 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
 	int irq_flags;
 	uint32_t chans_available;
 	char chan_name[BCM2835_DMA_CHAN_NAME_SIZE];
+	unsigned int chan_start, chan_end;
 
 	cfg = of_device_get_match_data(&pdev->dev);
 	if (!cfg)
@@ -987,12 +991,18 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
 
 	dma_set_max_seg_size(&pdev->dev, 0x3FFFFFFF);
 
-	base = devm_platform_ioremap_resource(pdev, 0);
+	base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
 	if (IS_ERR(base))
 		return PTR_ERR(base);
 
+	chan_start = (res->start / BCM2835_DMA_CHAN_SIZE) & 0xf;
+	chan_end = min_t(unsigned int,
+			 chan_start + resource_size(res) / BCM2835_DMA_CHAN_SIZE,
+			 BCM2835_DMA_MAX_DMA_CHAN_SUPPORTED + 1);
+
 	od->base = base;
 	od->cfg = cfg;
+	od->first_chan = chan_start;
 
 	dma_cap_set(DMA_SLAVE, od->ddev.cap_mask);
 	dma_cap_set(DMA_PRIVATE, od->ddev.cap_mask);
@@ -1037,12 +1047,13 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
 	}
 
 	/* get irqs for each channel that we support */
-	for (i = 0; i <= BCM2835_DMA_MAX_DMA_CHAN_SUPPORTED; i++) {
+	for (i = 0; i <= BCM2835_DMA_MAX_DMA_CHAN_SUPPORTED; i++)
+		irq[i] = -1;
+
+	for (i = chan_start; i < chan_end; i++) {
 		/* skip masked out channels */
-		if (!(chans_available & (1 << i))) {
-			irq[i] = -1;
+		if (!(chans_available & (1 << i)))
 			continue;
-		}
 
 		/* get the named irq */
 		snprintf(chan_name, sizeof(chan_name), "dma%i", i);
@@ -1057,11 +1068,11 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
 		 * in case of channel >= 11
 		 * use the 11th interrupt and that is shared
 		 */
-		irq[i] = platform_get_irq(pdev, i < 11 ? i : 11);
+		irq[i] = platform_get_irq(pdev, min(i - chan_start, 11U));
 	}
 
 	/* get irqs for each channel */
-	for (i = 0; i <= BCM2835_DMA_MAX_DMA_CHAN_SUPPORTED; i++) {
+	for (i = chan_start; i < chan_end; i++) {
 		/* skip channels without irq */
 		if (irq[i] < 0)
 			continue;
@@ -1080,7 +1091,8 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
 			goto err_no_dma;
 	}
 
-	dev_dbg(&pdev->dev, "Initialized %i DMA channels\n", i);
+	dev_dbg(&pdev->dev, "Initialized DMA channels %u-%u\n", chan_start,
+		chan_end - 1);
 
 	/* Device-tree DMA controller registration */
 	rc = of_dma_controller_register(pdev->dev.of_node,
-- 
2.56.0