async_tx: make async_tx channel switching opt-in

The majority of drivers in drivers/dma/ will never establish cross
channel operation chains and do not need the extra overhead in struct
dma_async_tx_descriptor.  Make channel switching opt-in by default.

Cc: Anatolij Gustschin <agust@denx.de>
Cc: Ira Snyder <iws@ovro.caltech.edu>
Cc: Linus Walleij <linus.walleij@stericsson.com>
Cc: Saeed Bishara <saeed@marvell.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 235153cd7ac5..8bcb15fb959d 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -706,7 +706,7 @@ int dma_async_device_register(struct dma_device *device)
         BUG_ON(!device->dev);
 
         /* note: this only matters in the
-         * CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH=y case
+         * CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH=n case
          */
         if (device_has_all_tx_types(device))
                 dma_cap_set(DMA_ASYNC_TX, device->cap_mask);
@@ -980,7 +980,7 @@ void dma_async_tx_descriptor_init(struct dma_async_tx_descriptor *tx,
         struct dma_chan *chan)
 {
         tx->chan = chan;
-        #ifndef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
+        #ifdef CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH
         spin_lock_init(&tx->lock);
         #endif
 }