4 files changed, 37 insertions, 75 deletions

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 1b2df59d1d65..93f7992bee5c 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -560,7 +560,7 @@ EXPORT_SYMBOL_GPL(__dma_request_channel);
  * @dev:        pointer to client device structure
  * @name:       slave channel name
  */
-struct dma_chan *dma_request_slave_channel(struct device *dev, char *name)
+struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name)
 {
         /* If device-tree is present get slave info from here */
         if (dev->of_node)
diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
index 69d04d28b1ef..7aa0864cd487 100644
--- a/drivers/dma/of-dma.c
+++ b/drivers/dma/of-dma.c
@@ -13,43 +13,31 @@
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/module.h>
-#include <linux/rculist.h>
+#include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/of.h>
 #include <linux/of_dma.h>
 
 static LIST_HEAD(of_dma_list);
-static DEFINE_SPINLOCK(of_dma_lock);
+static DEFINE_MUTEX(of_dma_lock);
 
 /**
- * of_dma_get_controller - Get a DMA controller in DT DMA helpers list
+ * of_dma_find_controller - Get a DMA controller in DT DMA helpers list
  * @dma_spec:   pointer to DMA specifier as found in the device tree
  *
  * Finds a DMA controller with matching device node and number for dma cells
- * in a list of registered DMA controllers. If a match is found the use_count
- * variable is increased and a valid pointer to the DMA data stored is retuned.
- * A NULL pointer is returned if no match is found.
+ * in a list of registered DMA controllers. If a match is found a valid pointer
+ * to the DMA data stored is retuned. A NULL pointer is returned if no match is
+ * found.
  */
-static struct of_dma *of_dma_get_controller(struct of_phandle_args *dma_spec)
+static struct of_dma *of_dma_find_controller(struct of_phandle_args *dma_spec)
 {
         struct of_dma *ofdma;
 
-        spin_lock(&of_dma_lock);
-
-        if (list_empty(&of_dma_list)) {
-                spin_unlock(&of_dma_lock);
-                return NULL;
-        }
-
         list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
                 if ((ofdma->of_node == dma_spec->np) &&
-                    (ofdma->of_dma_nbcells == dma_spec->args_count)) {
-                        ofdma->use_count++;
-                        spin_unlock(&of_dma_lock);
+                    (ofdma->of_dma_nbcells == dma_spec->args_count))
                         return ofdma;
-                }
-
-        spin_unlock(&of_dma_lock);
 
         pr_debug("%s: can't find DMA controller %s\n", __func__,
                  dma_spec->np->full_name);
@@ -58,22 +46,6 @@ static struct of_dma *of_dma_get_controller(struct of_phandle_args *dma_spec)
 }
 
 /**
- * of_dma_put_controller - Decrement use count for a registered DMA controller
- * @of_dma:     pointer to DMA controller data
- *
- * Decrements the use_count variable in the DMA data structure. This function
- * should be called only when a valid pointer is returned from
- * of_dma_get_controller() and no further accesses to data referenced by that
- * pointer are needed.
- */
-static void of_dma_put_controller(struct of_dma *ofdma)
-{
-        spin_lock(&of_dma_lock);
-        ofdma->use_count--;
-        spin_unlock(&of_dma_lock);
-}
-
-/**
  * of_dma_controller_register - Register a DMA controller to DT DMA helpers
  * @np:                 device node of DMA controller
  * @of_dma_xlate:       translation function which converts a phandle
@@ -93,6 +65,7 @@ int of_dma_controller_register(struct device_node *np,
 {
         struct of_dma   *ofdma;
         int             nbcells;
+        const __be32    *prop;
 
         if (!np || !of_dma_xlate) {
                 pr_err("%s: not enough information provided\n", __func__);
@@ -103,8 +76,11 @@ int of_dma_controller_register(struct device_node *np,
         if (!ofdma)
                 return -ENOMEM;
 
-        nbcells = be32_to_cpup(of_get_property(np, "#dma-cells", NULL));
-        if (!nbcells) {
+        prop = of_get_property(np, "#dma-cells", NULL);
+        if (prop)
+                nbcells = be32_to_cpup(prop);
+
+        if (!prop || !nbcells) {
                 pr_err("%s: #dma-cells property is missing or invalid\n",
                        __func__);
                 kfree(ofdma);
@@ -115,12 +91,11 @@ int of_dma_controller_register(struct device_node *np,
         ofdma->of_dma_nbcells = nbcells;
         ofdma->of_dma_xlate = of_dma_xlate;
         ofdma->of_dma_data = data;
-        ofdma->use_count = 0;
 
         /* Now queue of_dma controller structure in list */
-        spin_lock(&of_dma_lock);
+        mutex_lock(&of_dma_lock);
         list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
-        spin_unlock(&of_dma_lock);
+        mutex_unlock(&of_dma_lock);
 
         return 0;
 }
@@ -132,32 +107,20 @@ EXPORT_SYMBOL_GPL(of_dma_controller_register);
  *
  * Memory allocated by of_dma_controller_register() is freed here.
  */
-int of_dma_controller_free(struct device_node *np)
+void of_dma_controller_free(struct device_node *np)
 {
         struct of_dma *ofdma;
 
-        spin_lock(&of_dma_lock);
-
-        if (list_empty(&of_dma_list)) {
-                spin_unlock(&of_dma_lock);
-                return -ENODEV;
-        }
+        mutex_lock(&of_dma_lock);
 
         list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
                 if (ofdma->of_node == np) {
-                        if (ofdma->use_count) {
-                                spin_unlock(&of_dma_lock);
-                                return -EBUSY;
-                        }
-
                         list_del(&ofdma->of_dma_controllers);
-                        spin_unlock(&of_dma_lock);
                         kfree(ofdma);
-                        return 0;
+                        break;
                 }
 
-        spin_unlock(&of_dma_lock);
-        return -ENODEV;
+        mutex_unlock(&of_dma_lock);
 }
 EXPORT_SYMBOL_GPL(of_dma_controller_free);
 
@@ -172,8 +135,8 @@ EXPORT_SYMBOL_GPL(of_dma_controller_free);
  * specifiers, matches the name provided. Returns 0 if the name matches and
  * a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
  */
-static int of_dma_match_channel(struct device_node *np, char *name, int index,
-                                struct of_phandle_args *dma_spec)
+static int of_dma_match_channel(struct device_node *np, const char *name,
+                                int index, struct of_phandle_args *dma_spec)
 {
         const char *s;
 
@@ -198,7 +161,7 @@ static int of_dma_match_channel(struct device_node *np, char *name, int index,
  * Returns pointer to appropriate dma channel on success or NULL on error.
  */
 struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
-                                              char *name)
+                                              const char *name)
 {
         struct of_phandle_args  dma_spec;
         struct of_dma           *ofdma;
@@ -220,14 +183,15 @@ struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
                 if (of_dma_match_channel(np, name, i, &dma_spec))
                         continue;
 
-                ofdma = of_dma_get_controller(&dma_spec);
-
-                if (!ofdma)
-                        continue;
+                mutex_lock(&of_dma_lock);
+                ofdma = of_dma_find_controller(&dma_spec);
 
-                chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
+                if (ofdma)
+                        chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
+                else
+                        chan = NULL;
 
-                of_dma_put_controller(ofdma);
+                mutex_unlock(&of_dma_lock);
 
                 of_node_put(dma_spec.np);
 
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index dd6d21b335c8..96d3e4ab11a9 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -969,7 +969,7 @@ enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx);
 void dma_issue_pending_all(void);
 struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
                                         dma_filter_fn fn, void *fn_param);
-struct dma_chan *dma_request_slave_channel(struct device *dev, char *name);
+struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name);
 void dma_release_channel(struct dma_chan *chan);
 #else
 static inline enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
@@ -985,7 +985,7 @@ static inline struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
         return NULL;
 }
 static inline struct dma_chan *dma_request_slave_channel(struct device *dev,
-                                                         char *name)
+                                                         const char *name)
 {
         return NULL;
 }
diff --git a/include/linux/of_dma.h b/include/linux/of_dma.h
index d15073e080dd..364dda734877 100644
--- a/include/linux/of_dma.h
+++ b/include/linux/of_dma.h
@@ -25,7 +25,6 @@ struct of_dma {
         struct dma_chan         *(*of_dma_xlate)
                                 (struct of_phandle_args *, struct of_dma *);
         void                    *of_dma_data;
-        int                     use_count;
 };
 
 struct of_dma_filter_info {
@@ -38,9 +37,9 @@ extern int of_dma_controller_register(struct device_node *np,
                 struct dma_chan *(*of_dma_xlate)
                 (struct of_phandle_args *, struct of_dma *),
                 void *data);
-extern int of_dma_controller_free(struct device_node *np);
+extern void of_dma_controller_free(struct device_node *np);
 extern struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
-                                                     char *name);
+                                                     const char *name);
 extern struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
                 struct of_dma *ofdma);
 #else
@@ -52,13 +51,12 @@ static inline int of_dma_controller_register(struct device_node *np,
         return -ENODEV;
 }
 
-static inline int of_dma_controller_free(struct device_node *np)
+static inline void of_dma_controller_free(struct device_node *np)
 {
-        return -ENODEV;
 }
 
 static inline struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
-                                                     char *name)
+                                                     const char *name)
 {
         return NULL;
 }