Re: [PATCH 4/5] dmaengine: dw: Ignore burst setting for memory peripherals

Andy Shevchenko
2020-07-30T16:31:31Z

On Thu, Jul 30, 2020 at 06:45:44PM +0300, Serge Semin wrote:
> According to the DW DMA controller Databook (page 40 "3.5 Memory

Which version of it?

> Peripherals") memory peripherals don't have handshaking interface
> connected to the controller, therefore they can never be a flow
> controller. Since the CTLx.SRC_MSIZE and CTLx.DEST_MSIZE are
> properties valid only for peripherals with a handshaking
> interface, we can freely zero these fields out if the memory peripheral
> is selected to be the source or the destination of the DMA transfers.
>
> Note according to the databook, length of burst transfers to memory is
> always equal to the number of data items available in a channel FIFO or
> data items required to complete the block transfer, whichever is smaller;
> length of burst transfers from memory is always equal to the space
> available in a channel FIFO or number of data items required to complete
> the block transfer, whichever is smaller.

But does it really matter if you program there something or not?

--
With Best Regards,
Andy Shevchenko