On Mon, 2013-01-21 at 00:49 -0800, Vinod Koul wrote: > On Mon, Jan 21, 2013 at 11:00:44AM +0200, Andy Shevchenko wrote: > > Currently the driver returns full length of the active descriptor which is > > wrong. We have to go throught the active descriptor and sum up the length of > > unsent children in the chain along with the actual data in the DMA channel > why do you mean by children here?
The list nodes chained under (active) &desc->tx_list. > > registers. > > > > The cyclic case is not handled by this patch due to len field in the > > descriptor > > structure is left untouched by the original code. > > > > Signed-off-by: Andy Shevchenko <[email protected]> > > --- > > drivers/dma/dw_dmac.c | 93 > > ++++++++++++++++++++++++++++++++++++++++++++++++- > > 1 file changed, 92 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c > > index d1b9ba2..4325c68 100644 > > --- a/drivers/dma/dw_dmac.c > > +++ b/drivers/dma/dw_dmac.c > > @@ -941,6 +941,97 @@ err_desc_get: > > return NULL; > > } > > > > +/* --------------------- Calculate residue ---------------------------- */ > > + > > +static inline size_t dwc_get_rest(struct dw_dma_chan *dwc, struct dw_desc > > *desc) > > +{ > > + enum dma_transfer_direction direction = dwc->direction; > > + > > + if (direction == DMA_MEM_TO_DEV || direction == DMA_MEM_TO_MEM) > > + return desc->len - (channel_readl(dwc, SAR) - desc->lli.sar); > > + else if (direction == DMA_DEV_TO_MEM) > > + return desc->len - (channel_readl(dwc, DAR) - desc->lli.dar); > > + > > + return 0; > hmmm, why not use BLOCK_TS value. That way you dont need to look at direction > and along with burst can easily calculate residue... Do you mean to read CTL hi/lo and do desc->len - ctlhi.block_ts * ctllo.src_tr_width? I think it could be not precise when memory-to-peripheral transfer is going on. In that case you probably will have src_tr_width like 32 bits, meanwhile peripheral may receive only byte stream. -- Andy Shevchenko <[email protected]> Intel Finland Oy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
