dmaengine: bcm2835: add slave_sg support to bcm2835-dma

Add slave_sg support to bcm2835-dma using shared allocation
code for bcm2835_desc and DMA-control blocks already used by
dma_cyclic.

Note that bcm2835_dma_callback had to get modified to support
both modes of operation (cyclic and non-cyclic).

Tested using:
* Hifiberry I2S card (using cyclic DMA)
* fb_st7735r SPI-framebuffer (using slave_sg DMA via spi-bcm2835)
playing BigBuckBunny for audio and video.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

1 files changed, 108 insertions, 5 deletions

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index 59c5ef36d970..b46b12f66f38 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -260,6 +260,23 @@ static void bcm2835_dma_create_cb_set_length(
         control_block->info |= finalextrainfo;
 }
 
+static inline size_t bcm2835_dma_count_frames_for_sg(
+        struct bcm2835_chan *c,
+        struct scatterlist *sgl,
+        unsigned int sg_len)
+{
+        size_t frames = 0;
+        struct scatterlist *sgent;
+        unsigned int i;
+        size_t plength = bcm2835_dma_max_frame_length(c);
+
+        for_each_sg(sgl, sgent, sg_len, i)
+                frames += bcm2835_dma_frames_for_length(
+                        sg_dma_len(sgent), plength);
+
+        return frames;
+}
+
 /**
  * bcm2835_dma_create_cb_chain - create a control block and fills data in
  *
@@ -361,6 +378,32 @@ error_cb:
         return NULL;
 }
 
+static void bcm2835_dma_fill_cb_chain_with_sg(
+        struct dma_chan *chan,
+        enum dma_transfer_direction direction,
+        struct bcm2835_cb_entry *cb,
+        struct scatterlist *sgl,
+        unsigned int sg_len)
+{
+        struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
+        size_t max_len = bcm2835_dma_max_frame_length(c);
+        unsigned int i, len;
+        dma_addr_t addr;
+        struct scatterlist *sgent;
+
+        for_each_sg(sgl, sgent, sg_len, i) {
+                for (addr = sg_dma_address(sgent), len = sg_dma_len(sgent);
+                     len > 0;
+                     addr += cb->cb->length, len -= cb->cb->length, cb++) {
+                        if (direction == DMA_DEV_TO_MEM)
+                                cb->cb->dst = addr;
+                        else
+                                cb->cb->src = addr;
+                        cb->cb->length = min(len, max_len);
+                }
+        }
+}
+
 static int bcm2835_dma_abort(void __iomem *chan_base)
 {
         unsigned long cs;
@@ -428,13 +471,19 @@ static irqreturn_t bcm2835_dma_callback(int irq, void *data)
         d = c->desc;
 
         if (d) {
-                /* TODO Only works for cyclic DMA */
-                vchan_cyclic_callback(&d->vd);
+                if (d->cyclic) {
+                        /* call the cyclic callback */
+                        vchan_cyclic_callback(&d->vd);
+
+                        /* Keep the DMA engine running */
+                        writel(BCM2835_DMA_ACTIVE,
+                               c->chan_base + BCM2835_DMA_CS);
+                } else {
+                        vchan_cookie_complete(&c->desc->vd);
+                        bcm2835_dma_start_desc(c);
+                }
         }
 
-        /* Keep the DMA engine running */
-        writel(BCM2835_DMA_ACTIVE, c->chan_base + BCM2835_DMA_CS);
-
         spin_unlock_irqrestore(&c->vc.lock, flags);
 
         return IRQ_HANDLED;
@@ -548,6 +597,58 @@ static void bcm2835_dma_issue_pending(struct dma_chan *chan)
         spin_unlock_irqrestore(&c->vc.lock, flags);
 }
 
+static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
+        struct dma_chan *chan,
+        struct scatterlist *sgl, unsigned int sg_len,
+        enum dma_transfer_direction direction,
+        unsigned long flags, void *context)
+{
+        struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
+        struct bcm2835_desc *d;
+        dma_addr_t src = 0, dst = 0;
+        u32 info = BCM2835_DMA_WAIT_RESP;
+        u32 extra = BCM2835_DMA_INT_EN;
+        size_t frames;
+
+        if (!is_slave_direction(direction)) {
+                dev_err(chan->device->dev,
+                        "%s: bad direction?\n", __func__);
+                return NULL;
+        }
+
+        if (c->dreq != 0)
+                info |= BCM2835_DMA_PER_MAP(c->dreq);
+
+        if (direction == DMA_DEV_TO_MEM) {
+                if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
+                        return NULL;
+                src = c->cfg.src_addr;
+                info |= BCM2835_DMA_S_DREQ | BCM2835_DMA_D_INC;
+        } else {
+                if (c->cfg.dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
+                        return NULL;
+                dst = c->cfg.dst_addr;
+                info |= BCM2835_DMA_D_DREQ | BCM2835_DMA_S_INC;
+        }
+
+        /* count frames in sg list */
+        frames = bcm2835_dma_count_frames_for_sg(c, sgl, sg_len);
+
+        /* allocate the CB chain */
+        d = bcm2835_dma_create_cb_chain(chan, direction, false,
+                                        info, extra,
+                                        frames, src, dst, 0, 0,
+                                        GFP_KERNEL);
+        if (!d)
+                return NULL;
+
+        /* fill in frames with scatterlist pointers */
+        bcm2835_dma_fill_cb_chain_with_sg(chan, direction, d->cb_list,
+                                          sgl, sg_len);
+
+        return vchan_tx_prep(&c->vc, &d->vd, flags);
+}
+
 static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
         struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
         size_t period_len, enum dma_transfer_direction direction,
@@ -778,11 +879,13 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
         dma_cap_set(DMA_SLAVE, od->ddev.cap_mask);
         dma_cap_set(DMA_PRIVATE, od->ddev.cap_mask);
         dma_cap_set(DMA_CYCLIC, od->ddev.cap_mask);
+        dma_cap_set(DMA_SLAVE, od->ddev.cap_mask);
         od->ddev.device_alloc_chan_resources = bcm2835_dma_alloc_chan_resources;
         od->ddev.device_free_chan_resources = bcm2835_dma_free_chan_resources;
         od->ddev.device_tx_status = bcm2835_dma_tx_status;
         od->ddev.device_issue_pending = bcm2835_dma_issue_pending;
         od->ddev.device_prep_dma_cyclic = bcm2835_dma_prep_dma_cyclic;
+        od->ddev.device_prep_slave_sg = bcm2835_dma_prep_slave_sg;
         od->ddev.device_config = bcm2835_dma_slave_config;
         od->ddev.device_terminate_all = bcm2835_dma_terminate_all;
         od->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);