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

sudheer.v
2018-10-26T07:03:51Z

On Sat, Oct 20, 2018 at 09:56:24PM +0530, Vinod wrote:
> On 19-10-18, 12:41, sudheer.v wrote:
> > 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.
>
>
> My advise would be to see what you can do with the DMA IP block. If this
> can/would be used in different places then it would make sense to do a
> dmaengine driver and solve the problem for everyone.
>
> If this is always going to be hidden behind serial then maybe it makes
> sense to be inside serial driver and not use dmaengine APIs
>
> If you decide to prefer the former case, please move it to dmaengine and
> resubmit :)
>
> HTH
> --
> ~Vinod

Hi All,
As the DMA engine is dedicated only to UART,we have decided
to rewrite the driver so that no code will come under
drivers/dma.

I will resubmitt the patches after merging dma controller
code and uart driver code.
Regards
-sudheer