dma: mmp_pdma: make the controller a DMA provider

This patch makes the mmp_pdma controller able to provide DMA resources
in DT environments by providing an dma xlate function.

of_dma_simple_xlate() isn't used here, because if fails to handle
multiple different DMA engines or several instances of the same
controller. Instead, a private implementation is provided that makes use
of the newly introduced dma_get_slave_channel() call.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/drivers/dma/mmp_pdma.c b/drivers/dma/mmp_pdma.c
index dd024d4759e7..76884c48ea85 100644
--- a/drivers/dma/mmp_pdma.c
+++ b/drivers/dma/mmp_pdma.c
@@ -18,6 +18,7 @@
 #include <linux/platform_data/mmp_dma.h>
 #include <linux/dmapool.h>
 #include <linux/of_device.h>
+#include <linux/of_dma.h>
 #include <linux/of.h>
 #include <linux/dma/mmp-pdma.h>
 
@@ -777,6 +778,39 @@ static struct of_device_id mmp_pdma_dt_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, mmp_pdma_dt_ids);
 
+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;
+
+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)
+                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;
+        }
+
+        goto retry;
+}
+
 static int mmp_pdma_probe(struct platform_device *op)
 {
         struct mmp_pdma_device *pdev;
@@ -863,6 +897,16 @@ static int mmp_pdma_probe(struct platform_device *op)
                 return ret;
         }
 
+        if (op->dev.of_node) {
+                /* Device-tree DMA controller registration */
+                ret = of_dma_controller_register(op->dev.of_node,
+                                                 mmp_pdma_dma_xlate, pdev);
+                if (ret < 0) {
+                        dev_err(&op->dev, "of_dma_controller_register failed\n");
+                        return ret;
+                }
+        }
+
         dev_info(pdev->device.dev, "initialized\n");
         return 0;
 }