dma: add dma_get_any_slave_channel(), for use in of_xlate()

mmp_pdma.c implements a custom of_xlate() function that is 95% identical
to what Tegra will need. Create a function to implement the common part,
so everyone doesn't just cut/paste the implementation.

Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: dmaengine@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

2 files changed, 35 insertions, 23 deletions

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index ea806bdc12ef..4f08ee8c17b4 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -535,6 +535,34 @@ struct dma_chan *dma_get_slave_channel(struct dma_chan *chan)
 }
 EXPORT_SYMBOL_GPL(dma_get_slave_channel);
 
+struct dma_chan *dma_get_any_slave_channel(struct dma_device *device)
+{
+        dma_cap_mask_t mask;
+        struct dma_chan *chan;
+        int err;
+
+        dma_cap_zero(mask);
+        dma_cap_set(DMA_SLAVE, mask);
+
+        /* lock against __dma_request_channel */
+        mutex_lock(&dma_list_mutex);
+
+        chan = private_candidate(&mask, device, NULL, NULL);
+        if (chan) {
+                err = dma_chan_get(chan);
+                if (err) {
+                        pr_debug("%s: failed to get %s: (%d)\n",
+                                __func__, dma_chan_name(chan), err);
+                        chan = NULL;
+                }
+        }
+
+        mutex_unlock(&dma_list_mutex);
+
+        return chan;
+}
+EXPORT_SYMBOL_GPL(dma_get_any_slave_channel);
+
 /**
  * __dma_request_channel - try to allocate an exclusive channel
  * @mask: capabilities that the channel must satisfy
diff --git a/drivers/dma/mmp_pdma.c b/drivers/dma/mmp_pdma.c
index dcb1e05149a7..2998f1bffac1 100644
--- a/drivers/dma/mmp_pdma.c
+++ b/drivers/dma/mmp_pdma.c
@@ -893,33 +893,17 @@ static struct dma_chan *mmp_pdma_dma_xlate(struct of_phandle_args *dma_spec,
                                            struct of_dma *ofdma)
 {
         struct mmp_pdma_device *d = ofdma->of_dma_data;
-        struct dma_chan *chan, *candidate;
+        struct dma_chan *chan;
+        struct mmp_pdma_chan *c;
 
-retry:
-        candidate = NULL;
-
-        /* walk the list of channels registered with the current instance and
-         * find one that is currently unused */
-        list_for_each_entry(chan, &d->device.channels, device_node)
-                if (chan->client_count == 0) {
-                        candidate = chan;
-                        break;
-                }
-
-        if (!candidate)
+        chan = dma_get_any_slave_channel(&d->device);
+        if (!chan)
                 return NULL;
 
-        /* dma_get_slave_channel will return NULL if we lost a race between
-         * the lookup and the reservation */
-        chan = dma_get_slave_channel(candidate);
-
-        if (chan) {
-                struct mmp_pdma_chan *c = to_mmp_pdma_chan(chan);
-                c->drcmr = dma_spec->args[0];
-                return chan;
-        }
+        c = to_mmp_pdma_chan(chan);
+        c->drcmr = dma_spec->args[0];
 
-        goto retry;
+        return chan;
 }
 
 static int mmp_pdma_probe(struct platform_device *op)