dmaengine: PL08x: track mux usage on a per-channel basis.

Keep track of the number of descriptors currently using a MUX setting
on a per-channel basis.  This allows us to know when we have descriptors
queued somewhere which have been assigned a DMA request signal.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
index c203d2f..ac9fdcc 100644 (file)
--- a/drivers/dma/amba-pl08x.c
+++ b/drivers/dma/amba-pl08x.c
@@ -227,6 +227,7 @@ enum pl08x_dma_chan_state {
  * @waiting: a TX descriptor on this channel which is waiting for a physical
  * channel to become available
  * @signal: the physical DMA request signal which this channel is using
+ * @mux_use: count of descriptors using this DMA request signal setting
  */
 struct pl08x_dma_chan {
        struct dma_chan chan;
@@ -244,6 +245,7 @@ struct pl08x_dma_chan {
        bool slave;
        struct pl08x_txd *waiting;
        int signal;
+       unsigned mux_use;
 };
 
 /**
@@ -310,10 +312,12 @@ static int pl08x_request_mux(struct pl08x_dma_chan *plchan)
        const struct pl08x_platform_data *pd = plchan->host->pd;
        int ret;
 
-       if (pd->get_signal) {
+       if (plchan->mux_use++ == 0 && pd->get_signal) {
                ret = pd->get_signal(plchan->cd);
-               if (ret < 0)
+               if (ret < 0) {
+                       plchan->mux_use = 0;
                        return ret;
+               }
 
                plchan->signal = ret;
        }
@@ -324,9 +328,13 @@ static void pl08x_release_mux(struct pl08x_dma_chan *plchan)
 {
        const struct pl08x_platform_data *pd = plchan->host->pd;
 
-       if (plchan->signal >= 0 && pd->put_signal) {
-               pd->put_signal(plchan->cd, plchan->signal);
-               plchan->signal = -1;
+       if (plchan->signal >= 0) {
+               WARN_ON(plchan->mux_use == 0);
+
+               if (--plchan->mux_use == 0 && pd->put_signal) {
+                       pd->put_signal(plchan->cd, plchan->signal);
+                       plchan->signal = -1;
+               }
        }
 }