It turns out this check is too restrictive. The DMA API doesn't require
a 1:1 relation between mapping and sync. It's permissible to map a big
chunk and then managing it as a number of buffers that are synced
individually.
This is currently the case with the Designware MAC driver and having
this check here leads to a copious amount of false positives.
A proper check would involve keeping account of every individual cache
line and assigning it either a device or CPU owned flag in the common
code.
We'll implement this on top of KASAN in the follow-up commit, so let's
revert commit 1ad4b32702ddc3b801e8cd35441d2a9b3a41bb19 first to have
a clean slate.
Fixes: 1ad4b32702dd ("dma: debug: detect repeated DMA sync")
Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
---
drivers/dma/debug.c | 22 ++--------------------
1 file changed, 2 insertions(+), 20 deletions(-)
diff --git a/drivers/dma/debug.c b/drivers/dma/debug.c
index befe837d6cd8..7bf0be1e1ff3 100644
--- a/drivers/dma/debug.c
+++ b/drivers/dma/debug.c
@@ -13,7 +13,6 @@ struct dma_debug_entry {
dma_addr_t dev_addr;
size_t size;
int direction;
- bool dev_owned;
};
static const char *dir2name[] = {
@@ -123,7 +122,6 @@ void debug_dma_map(struct device *dev, void *addr,
entry->dev_addr = dev_addr;
entry->size = size;
entry->direction = direction;
- entry->dev_owned = true;
list_add(&entry->list, &dma_mappings);
@@ -166,17 +164,9 @@ 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_owned)
- 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_owned = false;
}
void debug_dma_sync_single_for_device(struct device *dev,
@@ -192,15 +182,7 @@ 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_owned)
- 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_owned = true;
}
--
2.39.2
