ARM: dts: am335x-evm: Enable NAND dma prefetch by default

Currently the default method of prefetch polled shows the highest
possible read and write speed when minimal non NAND background
activity is being done. But it is also very CPU intensive to reach
these high speeds (CPU load of 99% via mtd performance tests). While
DMA prefetch only uses 50% of the CPU to achieve around 23% less in
top read and write performance.

However, as the non NAND CPU load increases the read and write
performance takes a large hit when using polled prefetch. Therefore,
prefetch dma mode ends up outperforming prefetch polled in general
"system level" test. So switch to using dma prefetch by default since
it is likely what most users would prefer.

Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

diff --git a/arch/arm/boot/dts/am335x-evm.dts b/arch/arm/boot/dts/am335x-evm.dts
index 1c37a7c1ea17dd76fc2686c1bd9dd17acc250d99..ddd897556e035b6306306ca33eccc65c7ed45e3b 100644 (file)
--- a/arch/arm/boot/dts/am335x-evm.dts
+++ b/arch/arm/boot/dts/am335x-evm.dts
@@ -531,6 +531,7 @@
                interrupts = <0 IRQ_TYPE_NONE>, /* fifoevent */
                             <1 IRQ_TYPE_NONE>; /* termcount */
                rb-gpios = <&gpmc 0 GPIO_ACTIVE_HIGH>; /* gpmc_wait0 */
+               ti,nand-xfer-type = "prefetch-dma";
                ti,nand-ecc-opt = "bch8";
                ti,elm-id = <&elm>;
                nand-bus-width = <8>;