lkml.org 
[lkml]   [2011]   [Oct]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRE: [PATCHv4] DMAEngine: Define interleaved transfer request api
Date
From
On Tue, Oct 11, 2011 at 12:45 PM, Williams, Dan J
<dan.j.williams@intel.com> wrote:

> Subject: Re: [PATCHv4] DMAEngine: Define interleaved transfer request
> api
>
> [ Adding Alexandre ]
>
> On Fri, Oct 7, 2011 at 4:27 AM, Jassi Brar
<jaswinder.singh@linaro.org>
> wrote:
> > On 7 October 2011 11:15, Vinod Koul <vinod.koul@intel.com> wrote:
> >
> >> Thru this patch Jassi gave a very good try at merging DMA_SLAVE and
> >> memcpy, but more we debate this, I am still not convinced about
> merging
> >> memcpy and DMA_SLAVE yet.
> >>
> > Nobody is merging memcpy and DMA_SLAVE right away.
> > The api's primary purpose is to support interleave transfers.
> > Possibility to merge other prepares into this is a side-effect.
> >
> >> I would still argue that if we split this on same lines as current
> >> mechanism, we have clean way to convey all details for both cases.
> >>
> > Do you mean to have separate interleaved transfer apis for Slave
> > and Mem->Mem ? Please clarify.
> >
>
> This is a tangent, but it would be nice if this API extension also
> covered the needs of the incoming RapidIO case which wants to specify
> new device context information per operation (and not once at
> configuration time, like slave case). Would it be enough if the
> transfer template included a (struct device *context) member at the
> end? Most dma users could ignore it, but RapidIO could use it to do
> something like:
>
> struct rio_dev *rdev = container_of(context, typeof(*rdev),
device);
>
> That might not be enough, but I'm concerned that making the context a
> (void *) is too flexible. I'd rather have something like this than
> acquiring a lock in rio_dma_prep_slave_sg() and holding it over
> ->prep(). The alternative is to extend device_prep_slave_sg to take
> an extra parameter, but that impacts all other slave implementations
> with a dead parameter.
>

Having context limited to the device structure will not be enough for
RapidIO because of 66-bit target address (dma_addr_t will not work
here).
Probably that range is out of practical use at this moment but it is
defined by RIO specification and I would prefer to deal with it now
instead of postponing it for future. Passing context using (void *) will
solve this.

Alex.



\
 
 \ /
  Last update: 2011-10-14 19:53    [W:0.212 / U:1.292 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site