Messages in this thread | | | Subject | Re: [PATCH] dmaengine: add CSR SiRFprimaII DMAC driver | From | Vinod Koul <> | Date | Fri, 09 Sep 2011 03:16:18 +0530 |
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On Thu, 2011-09-08 at 10:55 +0530, Jassi Brar wrote: > 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). > > 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 > > 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? */; Looks like Jassi got a user for his proposed API. I am not sure whats going on with TI folks, they never showed up here @LPC.
-- ~Vinod Koul Intel Corp.
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