[PATCH] dma: debug: detect repeated DMA sync

[Ahmad Fatoum]

dma_map_single will do any necessary cache maintenance to make a buffer
available to a device. Calling debug_dma_sync_single_for_device on such
a buffer is unnecessary, so flag when this happens.

Signed-off-by: Ahmad Fatoum <a.fat...@pengutronix.de>
---
 drivers/dma/debug.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/debug.c b/drivers/dma/debug.c
index b3bfbff9b2f5..b80e35ff5092 100644
--- a/drivers/dma/debug.c
+++ b/drivers/dma/debug.c
@@ -12,6 +12,7 @@ struct dma_debug_entry {
        dma_addr_t       dev_addr;
        size_t           size;
        int              direction;
+       bool             dev_mapped;
 };
 
 static const char *dir2name[] = {
@@ -121,6 +122,7 @@ void debug_dma_map(struct device *dev, void *addr,
        entry->dev_addr = dev_addr;
        entry->size = size;
        entry->direction = direction;
+       entry->dev_mapped = true;
 
        list_add(&entry->list, &dma_mappings);
 
@@ -159,9 +161,17 @@ void debug_dma_sync_single_for_cpu(struct device *dev,
        struct dma_debug_entry *entry;
 
        entry = dma_debug_entry_find(dev, dma_handle, size);
-       if (!entry)
+       if (!entry) {
                dma_dev_warn(dev, "sync for CPU of never-mapped %s buffer 
0x%llx+0x%zx!\n",
                             dir2name[direction], (u64)dma_handle, size);
+               return;
+       }
+
+       if (!entry->dev_mapped)
+               dma_dev_warn(dev, "unexpected sync for CPU of already 
CPU-mapped %s buffer 0x%llx+0x%zx!\n",
+                            dir2name[direction], (u64)dma_handle, size);
+
+       entry->dev_mapped = false;
 }
 
 void debug_dma_sync_single_for_device(struct device *dev,
@@ -177,7 +187,15 @@ void debug_dma_sync_single_for_device(struct device *dev,
         * corruption
         */
        entry = dma_debug_entry_find(dev, dma_handle, size);
-       if (!entry)
+       if (!entry) {
                dma_dev_warn(dev, "Syncing for device of never-mapped %s buffer 
0x%llx+0x%zx!\n",
                             dir2name[direction], (u64)dma_handle, size);
+               return;
+       }
+
+       if (entry->dev_mapped)
+               dma_dev_warn(dev, "unexpected sync for device of already 
device-mapped %s buffer 0x%llx+0x%zx!\n",
+                            dir2name[direction], (u64)dma_handle, size);
+
+       entry->dev_mapped = true;
 }
-- 
2.39.2