On Mon, Jan 16, 2012 at 10:50 AM, Viresh Kumar [off-list ref] wrote:

Flow controller is programmable for few controllers and there are few
intelligent peripherals like, Synopsys JPEG controller, that needs to be a flow
controller of DMA transfers on dest side.

For this, currently two drivers, pl08x and dw_dmac, support flow controller to
be passed from platform to these drivers.

OK

Perhaps, this should be a part of struct dma_slave_config. This patch adds
another field device_fc to this structure. User drivers must pass this as true
if they want to be flow controller of certain transfers.

I dma_slave_config is supposed to be about info that

1) Must to be set-up at runtime
2) All DMA controllers need to know

So if it doesn't *have* to be set up by drivers at runtime, please keep it in
platform data.

If it is (1), so you have a use case where you have to switch a certain channel
between DMA master and device flow control at run-time it looks like it could
be useful for others as well, but I doubt this so I'd like some back-up on
that.

Yours,
Linus Walleij