Jassi Brar [mailto:jassisinghbrar@xxxxxxxxx] > Sent: Tuesday, August 23, 2011 2:42 PM > To: Boojin Kim > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-samsung- > soc@xxxxxxxxxxxxxxx; Vinod Koul; Kukjin Kim; Dan Williams; Mark Brown; > Grant Likely; Russell King > Subject: Re: [PATCH v6 04/15] DMA: PL330: Add DMA_CYCLIC capability > > On Mon, Aug 22, 2011 at 5:33 PM, Boojin Kim <boojin.kim@xxxxxxxxxxx> > wrote: > >> > >> > +static struct dma_async_tx_descriptor *pl330_prep_dma_cyclic( > >> > + struct dma_chan *chan, dma_addr_t dma_addr, size_t > len, > >> > + size_t period_len, enum dma_data_direction > direction) > >> > +{ > >> > + struct dma_pl330_desc *desc; > >> > + struct dma_pl330_chan *pch = to_pchan(chan); > >> > + dma_addr_t dst; > >> > + dma_addr_t src; > >> > + > >> > + desc = pl330_get_desc(pch); > >> > + if (!desc) { > >> > + dev_err(pch->dmac->pif.dev, "%s:%d Unable to fetch > >> desc\n", > >> > + __func__, __LINE__); > >> > + return NULL; > >> > + } > >> > + > >> > + switch (direction) { > >> > + case DMA_TO_DEVICE: > >> > + desc->rqcfg.src_inc = 1; > >> > + desc->rqcfg.dst_inc = 0; > >> > + src = dma_addr; > >> > + dst = pch->fifo_addr; > >> > + break; > >> > + case DMA_FROM_DEVICE: > >> > + desc->rqcfg.src_inc = 0; > >> > + desc->rqcfg.dst_inc = 1; > >> > + src = pch->fifo_addr; > >> > + dst = dma_addr; > >> > + break; > >> > + default: > >> > + dev_err(pch->dmac->pif.dev, "%s:%d Invalid dma > >> direction\n", > >> > + __func__, __LINE__); > >> > + return NULL; > >> > + } > >> > + > >> > + desc->rqcfg.brst_size = pch->burst_sz; > >> > + desc->rqcfg.brst_len = 1; > >> > + > >> > + if (!pch->cyclic) > >> > + pch->cyclic = CYCLIC_PREP; > >> The need for check here seems suspicious. > >> Is it really needed? If not, please remove it. > > It's required because Cyclic operation is passed from CYCLIC_PREP to > > CYCLIC_TRIGGER. > I don't see why you need to differentiate between PREP and TRIGGER in > cyclic mode. I think, you should simply have 'bool cyclic' instead of > enum. On cyclic mode, Pl330_tasklet() operation is changed according to the value of 'cyclic'. In case of CYCLIC_PREP, Pl330_tasklet()operation is same with normal operation. In case of CYCLIC_TRIGGER, pl330_tasklet()reloads the done data into work_list. So, 'Cyclic' needs two status(CYCLIC_PREP and CYCLIC_TRIGGER) to distinguish the operation on pl330_tasklet(). The sequence is following. device_prep_dma_cyclic() -> set CYCLIC_PREP -> device_issue_pending() -> Pl330_tasklet() with CYCLIC_PREP -> set CYCLIC_TRIGGER -> PL330 IRQ -> Pl330_tasklet() with CYCLIC_TRIGGER. Thanks Boojin -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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