SAMA5D3x: I2C, USART1 and DMA.
Peter Rosin
peda at lysator.liu.se
Wed Nov 25 03:55:33 PST 2015
Hi Sylvain,
On 2015-11-24 17:53, Sylvain Rochet wrote:
> On Tue, Nov 24, 2015 at 05:44:24PM +0100, Sylvain Rochet wrote:
>> On Tue, Nov 24, 2015 at 05:14:15PM +0100, Peter Rosin wrote:
>>> However, cutting out the "dmas" line does not improve things. So, how
>>> do I enable DMA on usart1?
>>
>> You are probably running out of available DMA channels on the DMAC0.
>> There is 8 channels available per DMAC and this is quite a scarce
>> resource.
>>
>> See "DMA Channels Definition" tables from the SAMA5D3 datasheet. I hope
>> you balanced well the peripherals you are using in your design on the
>> two DMAC to prevent running out of DMA channels.
>
> I forgot to add that you need to explicitely enable DMA on usart as
> explained in the Documentation/devicetree/bindings/serial/atmel-usart.txt
> documentation, this way:
>
> usart0: serial at f001c000 {
> ...
> atmel,use-dma-rx;
> atmel,use-dma-tx;
> ...
> }
Got it working, not dropped data yet... Thanks for the pointers!
Cheers,
Peter
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