[PATCH RFC] davinci: da850: define edma-memcpy-channels

[PATCH RFC] davinci: da850: define edma-memcpy-channels

[Adam Ford]

When booting with a device tree, message appears:
   memcpy is disabled
When reading through the bindings for eDMA3, it shows that
ti,edma-memcpy-channels is an optional property, but the example
binding uses it.

RFC:  I'll be the first to admit that I don't understand what
this is doing, but it seems like a DMA enabled memcpy would
improve performance.  Is this appropriate for da850?  Since there
are two eDMA3-tpcc controllers, is there a set of channels we can
use for each?

Signed-off-by: Adam Ford <aford173@gmail.com>

diff --git a/arch/arm/boot/dts/da850.dtsi b/arch/arm/boot/dts/da850.dtsi
index af68ef7..eacadb8 100644
--- a/arch/arm/boot/dts/da850.dtsi
+++ b/arch/arm/boot/dts/da850.dtsi
@@ -263,7 +263,7 @@
 			interrupts = <11 12>;
 			interrupt-names = "edma3_ccint", "edma3_ccerrint";
 			#dma-cells = <2>;
-
+			ti,edma-memcpy-channels = <20 21>;
 			ti,tptcs = <&edma0_tptc0 7>, <&edma0_tptc1 0>;
 		};
 		edma0_tptc0: tptc at 8000 {
-- 
2.7.4

[PATCH RFC] davinci: da850: define edma-memcpy-channels

[Sekhar Nori]

Hi Adam,

On Saturday 09 September 2017 05:58 PM, Adam Ford wrote:
> When booting with a device tree, message appears:
>    memcpy is disabled
> When reading through the bindings for eDMA3, it shows that
> ti,edma-memcpy-channels is an optional property, but the example
> binding uses it.
> 
> RFC:  I'll be the first to admit that I don't understand what
> this is doing, but it seems like a DMA enabled memcpy would
> improve performance.  Is this appropriate for da850?  Since there
> are two eDMA3-tpcc controllers, is there a set of channels we can
> use for each?
> 
> Signed-off-by: Adam Ford <aford173@gmail.com>

This enables DMA-based memcpy (see drivers/dma/dmaetest.c for example).
But does not accelerate any memcpy in kernel automatically.

If this is done, it should be done in a board specific manner because
the available channels you pick up for memcpy support can change from
board to board.

Thanks,
Sekhar