When running in software cyclic mode the driver currently does not go back
to the first segment once the last segment has been reached. Effectively
making the transfer non-cyclic.
Fix this by going back to the first segment once the last segment has been
reached for cyclic transfers.
Special care need to be taken to avoid a segment from being submitted
multiple times concurrently, which could happen for transfers with a number
of segments that is smaller than the DMA controller's internal queue.
Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
---
drivers/dma/dma-axi-dmac.c | 69 ++++++++++++++++++++++++++++++++++------------
1 file changed, 51 insertions(+), 18 deletions(-)
diff --git a/drivers/dma/dma-axi-dmac.c b/drivers/dma/dma-axi-dmac.c
index eb289aa187dd..2419fe524daa 100644
--- a/drivers/dma/dma-axi-dmac.c
+++ b/drivers/dma/dma-axi-dmac.c
@@ -72,6 +72,9 @@
#define AXI_DMAC_FLAG_CYCLIC BIT(0)
+/* The maximum ID allocated by the hardware is 31 */
+#define AXI_DMAC_SG_UNUSED 32U
+
struct axi_dmac_sg {
dma_addr_t src_addr;
dma_addr_t dest_addr;
@@ -80,6 +83,7 @@ struct axi_dmac_sg {
unsigned int dest_stride;
unsigned int src_stride;
unsigned int id;
+ bool schedule_when_free;
};
struct axi_dmac_desc {
@@ -200,11 +204,21 @@ static void axi_dmac_start_transfer(struct axi_dmac_chan *chan)
}
sg = &desc->sg[desc->num_submitted];
+ /* Already queued in cyclic mode. Wait for it to finish */
+ if (sg->id != AXI_DMAC_SG_UNUSED) {
+ sg->schedule_when_free = true;
+ return;
+ }
+
desc->num_submitted++;
- if (desc->num_submitted == desc->num_sgs)
- chan->next_desc = NULL;
- else
+ if (desc->num_submitted == desc->num_sgs) {
+ if (desc->cyclic)
+ desc->num_submitted = 0; /* Start again */
+ else
+ chan->next_desc = NULL;
+ } else {
chan->next_desc = desc;
+ }
sg->id = axi_dmac_read(dmac, AXI_DMAC_REG_TRANSFER_ID);
@@ -239,37 +253,52 @@ static struct axi_dmac_desc *axi_dmac_active_desc(struct axi_dmac_chan *chan)
struct axi_dmac_desc, vdesc.node);
}
-static void axi_dmac_transfer_done(struct axi_dmac_chan *chan,
+static bool axi_dmac_transfer_done(struct axi_dmac_chan *chan,
unsigned int completed_transfers)
{
struct axi_dmac_desc *active;
struct axi_dmac_sg *sg;
+ bool start_next = false;
active = axi_dmac_active_desc(chan);
if (!active)
- return;
+ return false;
- if (active->cyclic) {
- vchan_cyclic_callback(&active->vdesc);
- } else {
- do {
- sg = &active->sg[active->num_completed];
- if (!(BIT(sg->id) & completed_transfers))
- break;
- active->num_completed++;
- if (active->num_completed == active->num_sgs) {
+ do {
+ sg = &active->sg[active->num_completed];
+ if (sg->id == AXI_DMAC_SG_UNUSED) /* Not yet submitted */
+ break;
+ if (!(BIT(sg->id) & completed_transfers))
+ break;
+ active->num_completed++;
+ sg->id = AXI_DMAC_SG_UNUSED;
+ if (sg->schedule_when_free) {
+ sg->schedule_when_free = false;
+ start_next = true;
+ }
+
+ if (active->cyclic)
+ vchan_cyclic_callback(&active->vdesc);
+
+ if (active->num_completed == active->num_sgs) {
+ if (active->cyclic) {
+ active->num_completed = 0; /* wrap around */
+ } else {
list_del(&active->vdesc.node);
vchan_cookie_complete(&active->vdesc);
active = axi_dmac_active_desc(chan);
}
- } while (active);
- }
+ }
+ } while (active);
+
+ return start_next;
}
static irqreturn_t axi_dmac_interrupt_handler(int irq, void *devid)
{
struct axi_dmac *dmac = devid;
unsigned int pending;
+ bool start_next = false;
pending = axi_dmac_read(dmac, AXI_DMAC_REG_IRQ_PENDING);
if (!pending)
@@ -283,10 +312,10 @@ static irqreturn_t axi_dmac_interrupt_handler(int irq, void *devid)
unsigned int completed;
completed = axi_dmac_read(dmac, AXI_DMAC_REG_TRANSFER_DONE);
- axi_dmac_transfer_done(&dmac->chan, completed);
+ start_next = axi_dmac_transfer_done(&dmac->chan, completed);
}
/* Space has become available in the descriptor queue */
- if (pending & AXI_DMAC_IRQ_SOT)
+ if ((pending & AXI_DMAC_IRQ_SOT) || start_next)
axi_dmac_start_transfer(&dmac->chan);
spin_unlock(&dmac->chan.vchan.lock);
@@ -336,12 +365,16 @@ static void axi_dmac_issue_pending(struct dma_chan *c)
static struct axi_dmac_desc *axi_dmac_alloc_desc(unsigned int num_sgs)
{
struct axi_dmac_desc *desc;
+ unsigned int i;
desc = kzalloc(sizeof(struct axi_dmac_desc) +
sizeof(struct axi_dmac_sg) * num_sgs, GFP_NOWAIT);
if (!desc)
return NULL;
+ for (i = 0; i < num_sgs; i++)
+ desc->sg[i].id = AXI_DMAC_SG_UNUSED;
+
desc->num_sgs = num_sgs;
return desc;
--
2.11.0
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