dmaengine: stm32-dma: Rework starting transfer management

This patch reworks the way to manage transfer starting.
Now, starting DMA is only allowed when the channel is not busy.
Then, stm32_dma_start_transfer is declared as void.
At least, after each transfer completion, we start the next transfer if a
new descriptor as been queued in the issued list during an ongoing
transfer.

Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
Reviewed-by: Ludovic BARRE <ludovic.barre@st.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
index 3688d08..a8c2ad6 100644 (file)
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -421,7 +421,7 @@ static void stm32_dma_dump_reg(struct stm32_dma_chan *chan)
        dev_dbg(chan2dev(chan), "SFCR:  0x%08x\n", sfcr);
 }
 
-static int stm32_dma_start_transfer(struct stm32_dma_chan *chan)
+static void stm32_dma_start_transfer(struct stm32_dma_chan *chan)
 {
        struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
        struct virt_dma_desc *vdesc;
@@ -432,12 +432,12 @@ static int stm32_dma_start_transfer(struct stm32_dma_chan *chan)
 
        ret = stm32_dma_disable_chan(chan);
        if (ret < 0)
-               return ret;
+               return;
 
        if (!chan->desc) {
                vdesc = vchan_next_desc(&chan->vchan);
                if (!vdesc)
-                       return -EPERM;
+                       return;
 
                chan->desc = to_stm32_dma_desc(vdesc);
                chan->next_sg = 0;
@@ -471,7 +471,7 @@ static int stm32_dma_start_transfer(struct stm32_dma_chan *chan)
 
        chan->busy = true;
 
-       return 0;
+       dev_dbg(chan2dev(chan), "vchan %p: started\n", &chan->vchan);
 }
 
 static void stm32_dma_configure_next_sg(struct stm32_dma_chan *chan)
@@ -552,15 +552,13 @@ static void stm32_dma_issue_pending(struct dma_chan *c)
 {
        struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
        unsigned long flags;
-       int ret;
 
        spin_lock_irqsave(&chan->vchan.lock, flags);
-       if (!chan->busy) {
-               if (vchan_issue_pending(&chan->vchan) && !chan->desc) {
-                       ret = stm32_dma_start_transfer(chan);
-                       if ((!ret) && (chan->desc->cyclic))
-                               stm32_dma_configure_next_sg(chan);
-               }
+       if (vchan_issue_pending(&chan->vchan) && !chan->desc && !chan->busy) {
+               dev_dbg(chan2dev(chan), "vchan %p: issued\n", &chan->vchan);
+               stm32_dma_start_transfer(chan);
+               if (chan->desc->cyclic)
+                       stm32_dma_configure_next_sg(chan);
        }
        spin_unlock_irqrestore(&chan->vchan.lock, flags);
 }