Messages in this thread | | | From | Barry Song <> | Date | Thu, 8 Sep 2011 14:36:19 +0800 | Subject | Re: [PATCH] dmaengine: add CSR SiRFprimaII DMAC driver |
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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.
> > Anyways, every case can be easily expressed using the generic api > I proposed. See 'struct xfer_template' in https://lkml.org/lkml/2011/8/12/128
i think it is the interleaved DMA case and there is a inter-chunk-gap(ICG) between every chunk while dma_width > xlen, then your new generic API can definitely cover this case.
> > Roughly speaking, the following should be done... > Client driver :- > ************** > For a 'Rectangular' transfer (2d-dma.PNG) :- > xfer_template.numf = Ylen; /* height of rectangle */ > xfer_template.frame_size = 1; > xfer_template.sgl[0].size = Xlen; /* width of rectangle */ > xfer_template.sgl[0].icg = start_addr_Y(n) - end_addr_Y(n-1); > > For the "A Line and some" transfer (2d-dma2.PNG) :- > xfer_template.numf = 1; > xfer_template.frame_size = 2; > xfer_template.sgl[0].size = xlen1; /* a line */ > xfer_template.sgl[1].size = xlen2; /* and some */ > xfer_template.sgl[0].icg = start_addr_Y(n) - end_addr_Y(n-1); > xfer_template.sgl[1].icg = 0; /* doesn't matter */ > > DMAC driver :- > *************** > if (xfer_template.frame_size == 1) { > /* rectangle */ > schan->xlen = xfer_template.sgl[0].size; > schan->width = schan->xlen + xfer_template.sgl[0].icg; > } else if (xfer_template.frame_size == 2 && > xfer_template.numf == 1 && > xfer_template.sgl[1].size == xfer_template.sgl[0].icg){ > /* a line and some */ > schan->xlen = xfer_template.sgl[0].size + xfer_template.sgl[1].size. > schan->width = xfer_template.sgl[0].size; > } else { > /* _Hardware_ doesn't support the transfer as such. * > return -EINVAL; > } > schan->ylen = xfer_template.numf /* -1? */; >
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