bcm2708-dmaengine: Use more DMA channels (but not 12)

1) Only the bcm2708_fb drivers uses the legacy DMA API, and
it requires a BULK-capable channel, so all other types
(FAST, NORMAL and LITE) can be made available to the regular
DMA API.

2) DMA channels 11-14 share an interrupt. The driver can't
handle this, so don't use channels 12-14 (12 was used, probably
because it appears to have an interrupt, but in reality that
interrupt is for activity on ANY channel). This may explain
a lockup encountered when running out of DMA channels.

The combined effect of this patch is to leave 7 DMA channels
available + channel 0 for bcm2708_fb via the legacy API.

See: #1110
     #1108

arch/arm/boot/dts/bcm2708_common.dtsi

@@ -59,11 +59,10 @@
  <1 24>,
  <1 25>,
  <1 26>,
- <1 27>,
- <1 28>;
+ <1 27>;
 
  #dma-cells = <1>;
- brcm,dma-channel-mask = <0x7f35>;
+ brcm,dma-channel-mask = <0x0f35>;
  };
 
  intc: interrupt-controller {

drivers/dma/bcm2708-dmaengine.c

@@ -184,7 +184,7 @@ static void vc_dmaman_init(struct vc_dmaman *dmaman, void __iomem *dma_base,
 }
 
 static int vc_dmaman_chan_alloc(struct vc_dmaman *dmaman,
- unsigned preferred_feature_set)
+ unsigned required_feature_set)
 {
  u32 chans;
  int chan = 0;
@@ -193,10 +193,8 @@ static int vc_dmaman_chan_alloc(struct vc_dmaman *dmaman,
  chans = dmaman->chan_available;
  for (feature = 0; feature < BCM_DMA_FEATURE_COUNT; feature++)
  /* select the subset of available channels with the desired
- feature so long as some of the candidate channels have that
- feature */
- if ((preferred_feature_set & (1 << feature)) &&
- (chans & dmaman->has_feature[feature]))
+ features */
+ if (required_feature_set & (1 << feature))
  chans &= dmaman->has_feature[feature];
 
  if (!chans)
@@ -228,7 +226,7 @@ static int vc_dmaman_chan_free(struct vc_dmaman *dmaman, int chan)
 
 /* DMA Manager Monitor */
 
-extern int bcm_dma_chan_alloc(unsigned preferred_feature_set,
+extern int bcm_dma_chan_alloc(unsigned required_feature_set,
  void __iomem **out_dma_base, int *out_dma_irq)
 {
  struct vc_dmaman *dmaman = g_dmaman;
@@ -240,7 +238,7 @@ extern int bcm_dma_chan_alloc(unsigned preferred_feature_set,
  return -ENODEV;
 
  mutex_lock(&dmaman->lock);
- chan = vc_dmaman_chan_alloc(dmaman, preferred_feature_set);
+ chan = vc_dmaman_chan_alloc(dmaman, required_feature_set);
  if (chan < 0)
  goto out;
 
@@ -442,6 +440,7 @@ static inline struct bcm2835_desc *to_bcm2835_dma_desc(
  return container_of(t, struct bcm2835_desc, vd.tx);
 }
 
+#if 0
 static void dma_dumpregs(struct bcm2835_chan *c)
 {
  pr_debug("-------------DMA DUMPREGS-------------\n");
@@ -457,6 +456,7 @@ static void dma_dumpregs(struct bcm2835_chan *c)
  readl(c->chan_base + BCM2835_DMA_NEXTCB));
  pr_debug("--------------------------------------\n");
 }
+#endif
 
 static void bcm2835_dma_desc_free(struct virt_dma_desc *vd)
 {
@@ -862,6 +862,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
  uint32_t len = sg_dma_len(sgent);
 
  for (j = 0; j < len; j += max_size) {
+ u32 waits;
  struct bcm2835_dma_cb *control_block =
  &d->control_block_base[i+splitct];
 
@@ -879,7 +880,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
  }
 
  /* Common part */
- u32 waits = SDHCI_BCM_DMA_WAITS;
+ waits = SDHCI_BCM_DMA_WAITS;
  if ((dma_debug >> 0) & 0x1f)
  waits = (dma_debug >> 0) & 0x1f;
  control_block->info |= BCM2835_DMA_WAITS(waits);
@@ -1074,6 +1075,14 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
  int rc;
  int i;
  int irq;
+#ifdef CONFIG_DMA_BCM2708_LEGACY
+ static const u32 wanted_features[] = {
+ BCM_DMA_FEATURE_FAST,
+ BCM_DMA_FEATURE_NORMAL,
+ BCM_DMA_FEATURE_LITE
+ };
+ int j;
+#endif
 
 
  if (!pdev->dev.dma_mask)
@@ -1120,20 +1129,24 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
 
  platform_set_drvdata(pdev, od);
 
- for (i = 0; i < 5; i++) {
+ for (i = 0, j = 0; j < ARRAY_SIZE(wanted_features);) {
+
  void __iomem *chan_base;
  int chan_id;
 
- chan_id = bcm_dma_chan_alloc(BCM_DMA_FEATURE_LITE,
- &chan_base,
- &irq);
+ chan_id = bcm_dma_chan_alloc(wanted_features[j],
+  &chan_base,
+  &irq);
 
- if (chan_id < 0)
- break;
+ if (chan_id < 0) {
+ j++;
+ continue;
+ }
 
  rc = bcm2708_dma_chan_init(od, chan_base, chan_id, irq);
  if (rc)
  goto err_no_dma;
+ i++;
  }
 
  if (pdev->dev.of_node) {
@@ -1146,6 +1159,8 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
  }
  }
 
+ dev_info(&pdev->dev, "Initialized %i DMA channels (+ 1 legacy)\n", i);
+
 #else
  rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
  if (rc)