lkml.org 
[lkml]   [2011]   [Sep]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] dmaengine: add CSR SiRFprimaII DMAC driver
From
Date
On Thu, 2011-09-08 at 14:36 +0800, Barry Song wrote:
> 2011/9/8 Jassi Brar <jassisinghbrar@gmail.com>:
> > On Thu, Sep 8, 2011 at 8:47 AM, Jassi Brar <jassisinghbrar@gmail.com> wrote:
> >> On Thu, Sep 8, 2011 at 7:42 AM, Barry Song <21cnbao@gmail.com> wrote:
> >>
> >>>>> it is much different with primacell based DMA like pl080, pl330.
> >>>>> prima2 has a self-defined DMAC IP. basically it is a 2D mode dma with
> >>>>> two scales X and Y and direct way to start and stop DMA.
> >>>>> every channel has fixed function to serve only one perpheral. so you
> >>>>> find we have a filter id.
> >>>> okay, what do you mean by 2D mode? Is it similar to what TI folks, Linus
> >>>> W and Jassi Brar posted RFC's on?
> >>>
> >>> In SiRFprimaII 2-D DMA, the system memory space is interpreted
> >>> as a 2-D layout instead of a linear 1-D layout. More specifically, the
> >>> system memory can be considered as
> >>> multiple data lines. The length of the data line is determined by the
> >>> user-selected DMA_WIDTH register.
> >>> The user can specify a data window that the user wants to access using
> >>> four parameters:
> >>> ■ Start address
> >>> ■ X length
> >>> ■ Y length
> >>> ■ Width
> >>>
> >>> The idea of a 2-D DMA is shown in figure 2d-dma.png attached.
> >>>
> >>> If you specifies the Y length as 0 or the X length equals to the DMA
> >>> width, then this 2-D DMA reduces to
> >>> 1-D. If the user configures the X length greater than the DMA width,
> >>> then the extra data is wrapped around
> >>> to the next data line, this may corrupt the DMA transfer for
> >>> multiple-line 2-D DMA. If this is a 1-D DMA, then
> >>> there is no issue. The attached diagram 2d-dma2.png shows the
> >>> wrap-around of the extra data in case the X length
> >>> greater than DMA width.
> >>
> >> Sorry, the role of DMA_WIDTH is not clear to me yet.
> >> In which case the user _must_ set {xlen > width} ?
> >>
> > Perhaps 2d-dma.PNG is inaccurate - it shouldn't depict any deltaX.
> > Doesn't xlen and width always start together ? If no, please don't read ahead.
> >
> > According to figures, {xlen > width} is to be set _only_ when a transfer
> > is divided into _exactly_ two chunks separated by gap _exactly_
> > equal to length of the second chunk (an extremely rare case).
>
> Sorry i didn't list related full information in datasheet in my early reply.
> we don't have the case of xlen > dma_width.
What is intended usage of the 2D dma?

In first diagram you sent, x length is first block length to transfer
and (dma_width - x_len) is length to skip, right?

So what is the second diagram about? Is this juts a case when notion of
xlen > dma_width? How much you transfer and how much you skip?

--
~Vinod Koul
Intel Corp.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2011-09-09 01:37    [W:0.367 / U:0.460 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site