Re: [[PATCH] 8/9] DMA-UART-Driver-for-AST2500

sudheer.v
2018-10-19T07:11:56Z

On Fri, Oct 19, 2018 at 10:32:24AM +1100, Benjamin Herrenschmidt wrote:
> On Thu, 2018-10-18 at 15:25 +0530, Vinod wrote:
> >
> > > It's not a dmaengine driver. It's a serial UART driver that happens to
> > > use a dedicated DMA engine.
> >
> > Then I see no reason for it to use dmaengine APIs. The framework allows
> > people to share a controller for many clients, but if you have dedicated
> > one then you may use it directly
>
> Well... the engine is shared by a few UARTs, they have dedicated rings
> but there's a common set of regs for interrupt handling etc.
>
> That said, I still think it could be contained within a UART driver,
> there's little benefit in adding the framework overhead, esp since
> these are really weak cores, any overhead will be felt.
>
> Ben.
>
> > > It's unclear whether it should be split into two drivers, or just have
> > > the serial driver directly use the dma engine since that engine is
> > > dedicated in HW to only work on those UARTs and nothing else...
> > >
> > > Cheers,
> > > Ben.

Initially we wanted to have a single driver,
however we had an informal discussion with one of the maintainer
and based on the feedback, followed the Linux DMA and UART architecture.

If this seperate DMA-engine driver adds more overhead than benifit,
we will merge them into a single UART driver and resubmitt the patches.
Vinod,
can this dma-controller driver sit under dma subsystem?.
or better to move it under UART framework.

Thank you.
-- Sudheer