[PATCH v3 07/11] dmaengine: bcm2835: move controlblock chain generation into separate method
kernel at martin.sperl.org
kernel at martin.sperl.org
Sat Mar 5 02:52:18 PST 2016
From: Martin Sperl <kernel at martin.sperl.org>
In preparation of adding slave_sg functionality this patch moves the
generation/allocation of bcm2835_desc and the building of
the corresponding DMA-control-block chain from bcm2835_dma_prep_dma_cyclic
into the newly created method bcm2835_dma_create_cb_chain.
Signed-off-by: Martin Sperl <kernel at martin.sperl.org>
---
drivers/dma/bcm2835-dma.c | 294 +++++++++++++++++++++++++++++++---------------
1 file changed, 198 insertions(+), 96 deletions(-)
diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index 23b01c5..1ae53b8 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -90,12 +90,12 @@ struct bcm2835_desc {
struct virt_dma_desc vd;
enum dma_transfer_direction dir;
- struct bcm2835_cb_entry *cb_list;
-
unsigned int frames;
size_t size;
bool cyclic;
+
+ struct bcm2835_cb_entry cb_list[];
};
#define BCM2835_DMA_CS 0x00
@@ -185,6 +185,13 @@ struct bcm2835_desc {
#define BCM2835_DMA_IRQ_SHARED_DEFAULT 11
#define BCM2835_DMA_IRQ_ALL_DEFAULT 12
+/* how many frames of max_len size do we need to transfer len bytes */
+static inline size_t bcm2835_dma_frames_for_length(size_t len,
+ size_t max_len)
+{
+ return DIV_ROUND_UP(len, max_len);
+}
+
static inline struct bcm2835_dmadev *to_bcm2835_dma_dev(struct dma_device *d)
{
return container_of(d, struct bcm2835_dmadev, ddev);
@@ -201,19 +208,161 @@ static inline struct bcm2835_desc *to_bcm2835_dma_desc(
return container_of(t, struct bcm2835_desc, vd.tx);
}
-static void bcm2835_dma_desc_free(struct virt_dma_desc *vd)
+static void bcm2835_dma_free_cb_chain(struct bcm2835_desc *desc)
{
- struct bcm2835_desc *desc = container_of(vd, struct bcm2835_desc, vd);
- int i;
+ size_t i;
for (i = 0; i < desc->frames; i++)
dma_pool_free(desc->c->cb_pool, desc->cb_list[i].cb,
desc->cb_list[i].paddr);
- kfree(desc->cb_list);
kfree(desc);
}
+static void bcm2835_dma_desc_free(struct virt_dma_desc *vd)
+{
+ bcm2835_dma_free_cb_chain(
+ container_of(vd, struct bcm2835_desc, vd));
+}
+
+static void bcm2835_dma_create_cb_set_length(
+ struct bcm2835_chan *chan,
+ struct bcm2835_dma_cb *control_block,
+ size_t len,
+ size_t period_len,
+ size_t *total_len,
+ u32 finalextrainfo)
+{
+ /* set the length */
+ control_block->length = len;
+
+ /* finished if we have no period_length */
+ if (!period_len)
+ return;
+
+ /*
+ * period_len means: that we need to generate
+ * transfers that are terminating at every
+ * multiple of period_len - this is typically
+ * used to set the interrupt flag in info
+ * which is required during cyclic transfers
+ */
+
+ /* have we filled in period_length yet? */
+ if (*total_len + control_block->length < period_len)
+ return;
+
+ /* calculate the length that remains to reach period_length */
+ control_block->length = period_len - *total_len;
+
+ /* reset total_length for next period */
+ *total_len = 0;
+
+ /* add extrainfo bits in info */
+ control_block->info |= finalextrainfo;
+}
+
+/**
+ * bcm2835_dma_create_cb_chain - create a control block and fills data in
+ *
+ * @chan: the @dma_chan for which we run this
+ * @direction: the direction in which we transfer
+ * @cyclic: it is a cyclic transfer
+ * @info: the default info bits to apply per controlblock
+ * @frames: number of controlblocks to allocate
+ * @src: the src address to assign (if the S_INC bit is set
+ * in @info, then it gets incremented)
+ * @dst: the dst address to assign (if the D_INC bit is set
+ * in @info, then it gets incremented)
+ * @buf_len: the full buffer length (may also be 0)
+ * @period_len: the period length when to apply @finalextrainfo
+ * in addition to the last transfer
+ * this will also break some control-blocks early
+ * @finalextrainfo: additional bits in last controlblock
+ * (or when period_len is reached in case of cyclic)
+ * @gfp: the GFP flag to use for allocation
+ */
+static struct bcm2835_desc *bcm2835_dma_create_cb_chain(
+ struct dma_chan *chan, enum dma_transfer_direction direction,
+ bool cyclic, u32 info, u32 finalextrainfo, size_t frames,
+ dma_addr_t src, dma_addr_t dst, size_t buf_len,
+ size_t period_len, gfp_t gfp)
+{
+ struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
+ size_t len = buf_len, total_len;
+ size_t frame;
+ struct bcm2835_desc *d;
+ struct bcm2835_cb_entry *cb_entry;
+ struct bcm2835_dma_cb *control_block;
+
+ /* allocate and setup the descriptor. */
+ d = kzalloc(sizeof(*d) + frames * sizeof(struct bcm2835_cb_entry),
+ gfp);
+ if (!d)
+ return NULL;
+
+ d->c = c;
+ d->dir = direction;
+ d->cyclic = cyclic;
+
+ /*
+ * Iterate over all frames, create a control block
+ * for each frame and link them together.
+ */
+ for (frame = 0, total_len = 0; frame < frames; d->frames++, frame++) {
+ cb_entry = &d->cb_list[frame];
+ cb_entry->cb = dma_pool_alloc(c->cb_pool, gfp,
+ &cb_entry->paddr);
+ if (!cb_entry->cb)
+ goto error_cb;
+
+ /* fill in the control block */
+ control_block = cb_entry->cb;
+ control_block->info = info;
+ control_block->src = src;
+ control_block->dst = dst;
+ control_block->stride = 0;
+ control_block->next = 0;
+ /* set up length in control_block if requested */
+ if (buf_len) {
+ /* calculate length honoring period_length */
+ bcm2835_dma_create_cb_set_length(
+ c, control_block,
+ len, period_len, &total_len,
+ cyclic ? finalextrainfo : 0);
+
+ /* calculate new remaining length */
+ len -= control_block->length;
+ }
+
+ /* link this the last controlblock */
+ if (frame)
+ d->cb_list[frame - 1].cb->next = cb_entry->paddr;
+
+ /* update src and dst and length */
+ if (src && (info & BCM2835_DMA_S_INC))
+ src += control_block->length;
+ if (dst && (info & BCM2835_DMA_D_INC))
+ dst += control_block->length;
+
+ /* Length of total transfer */
+ d->size += control_block->length;
+ }
+
+ /* the last frame requires extra flags */
+ d->cb_list[d->frames - 1].cb->info |= finalextrainfo;
+
+ /* detect a size missmatch */
+ if (buf_len && (d->size != buf_len))
+ goto error_cb;
+
+ return d;
+error_cb:
+ bcm2835_dma_free_cb_chain(d);
+
+ return NULL;
+}
+
static int bcm2835_dma_abort(void __iomem *chan_base)
{
unsigned long cs;
@@ -417,12 +566,11 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
unsigned long flags)
{
struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
- enum dma_slave_buswidth dev_width;
struct bcm2835_desc *d;
- dma_addr_t dev_addr;
- unsigned int es, sync_type;
- unsigned int frame;
- int i;
+ dma_addr_t src, dst;
+ u32 info = BCM2835_DMA_WAIT_RESP;
+ u32 extra = BCM2835_DMA_INT_EN;
+ size_t frames;
/* Grab configuration */
if (!is_slave_direction(direction)) {
@@ -430,104 +578,58 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
return NULL;
}
- if (direction == DMA_DEV_TO_MEM) {
- dev_addr = c->cfg.src_addr;
- dev_width = c->cfg.src_addr_width;
- sync_type = BCM2835_DMA_S_DREQ;
- } else {
- dev_addr = c->cfg.dst_addr;
- dev_width = c->cfg.dst_addr_width;
- sync_type = BCM2835_DMA_D_DREQ;
- }
-
- /* Bus width translates to the element size (ES) */
- switch (dev_width) {
- case DMA_SLAVE_BUSWIDTH_4_BYTES:
- es = BCM2835_DMA_DATA_TYPE_S32;
- break;
- default:
+ if (!buf_len) {
+ dev_err(chan->device->dev,
+ "%s: bad buffer length (= 0)\n", __func__);
return NULL;
}
- /* Now allocate and setup the descriptor. */
- d = kzalloc(sizeof(*d), GFP_NOWAIT);
- if (!d)
- return NULL;
+ /*
+ * warn if buf_len is not a multiple of period_len - this may leed
+ * to unexpected latencies for interrupts and thus audiable clicks
+ */
+ if (buf_len % period_len)
+ dev_warn_once(chan->device->dev,
+ "%s: buffer_length (%zd) is not a multiple of period_len (%zd)\n",
+ __func__, buf_len, period_len);
- d->c = c;
- d->dir = direction;
- d->frames = buf_len / period_len;
- d->cyclic = true;
+ /* Setup DREQ channel */
+ if (c->dreq != 0)
+ info |= BCM2835_DMA_PER_MAP(c->dreq);
- d->cb_list = kcalloc(d->frames, sizeof(*d->cb_list), GFP_KERNEL);
- if (!d->cb_list) {
- kfree(d);
- return NULL;
+ if (direction == DMA_DEV_TO_MEM) {
+ if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
+ return NULL;
+ src = c->cfg.src_addr;
+ dst = buf_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;
+ src = buf_addr;
+ info |= BCM2835_DMA_D_DREQ | BCM2835_DMA_S_INC;
}
- /* Allocate memory for control blocks */
- for (i = 0; i < d->frames; i++) {
- struct bcm2835_cb_entry *cb_entry = &d->cb_list[i];
- cb_entry->cb = dma_pool_zalloc(c->cb_pool, GFP_ATOMIC,
- &cb_entry->paddr);
- if (!cb_entry->cb)
- goto error_cb;
- }
+ /* calculate number of frames */
+ frames = DIV_ROUND_UP(buf_len, period_len);
/*
- * Iterate over all frames, create a control block
- * for each frame and link them together.
+ * allocate the CB chain
+ * note that we need to use GFP_NOWAIT, as the ALSA i2s dmaengine
+ * implementation calls prep_dma_cyclic with interrupts disabled.
*/
- for (frame = 0; frame < d->frames; frame++) {
- struct bcm2835_dma_cb *control_block = d->cb_list[frame].cb;
-
- /* Setup adresses */
- if (d->dir == DMA_DEV_TO_MEM) {
- control_block->info = BCM2835_DMA_D_INC;
- control_block->src = dev_addr;
- control_block->dst = buf_addr + frame * period_len;
- } else {
- control_block->info = BCM2835_DMA_S_INC;
- control_block->src = buf_addr + frame * period_len;
- control_block->dst = dev_addr;
- }
-
- /* Enable interrupt */
- control_block->info |= BCM2835_DMA_INT_EN;
-
- /* Setup synchronization */
- if (sync_type != 0)
- control_block->info |= sync_type;
-
- /* Setup DREQ channel */
- if (c->dreq != 0)
- control_block->info |=
- BCM2835_DMA_PER_MAP(c->dreq);
-
- /* Length of a frame */
- control_block->length = period_len;
- d->size += control_block->length;
+ d = bcm2835_dma_create_cb_chain(chan, direction, true,
+ info, extra,
+ frames, src, dst, buf_len,
+ period_len, GFP_NOWAIT);
+ if (!d)
+ return NULL;
- /*
- * Next block is the next frame.
- * This DMA engine driver currently only supports cyclic DMA.
- * Therefore, wrap around at number of frames.
- */
- control_block->next = d->cb_list[((frame + 1) % d->frames)].paddr;
- }
+ /* wrap around into a loop */
+ d->cb_list[d->frames - 1].cb->next = d->cb_list[0].paddr;
return vchan_tx_prep(&c->vc, &d->vd, flags);
-error_cb:
- i--;
- for (; i >= 0; i--) {
- struct bcm2835_cb_entry *cb_entry = &d->cb_list[i];
-
- dma_pool_free(c->cb_pool, cb_entry->cb, cb_entry->paddr);
- }
-
- kfree(d->cb_list);
- kfree(d);
- return NULL;
}
static int bcm2835_dma_slave_config(struct dma_chan *chan,
--
2.1.4
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