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Index: linux-3.12.27/drivers/spi/spi-atmel.c
===================================================================
--- linux-3.12.27.orig/drivers/spi/spi-atmel.c
+++ linux-3.12.27/drivers/spi/spi-atmel.c
@@ -187,7 +187,12 @@
/* use PIO for small transfers, avoiding DMA setup/teardown overhead and
* cache operations; better heuristics consider wordsize and bitrate.
*/
-#define DMA_MIN_BYTES 16
+
+/* MTS: set DMA_MIN_BYTES=0 to use DMA all the time due to Rx buffer issues
+ * when switching between smaller PIO and larger DMA transfers
+ * https://lkml.org/lkml/2013/10/21/534
+ */
+#define DMA_MIN_BYTES 0
struct atmel_spi_dma {
struct dma_chan *chan_rx;
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