On Tue, Aug 23, 2011 at 12:38 PM, Boojin Kim <boojin.kim@xxxxxxxxxxx> wrote: > 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. By 'normal' you mean non-cyclic, right? That doesn't seem correct to do. Once the desc has been marked cyclic by device_prep_dma_cyclic(), you shouldn't treat it like a non-cyclic anymore. > 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. "device_issue_pending() ->Pl330_tasklet() with CYCLIC_PREP" is no different from "device_issue_pending() ->Pl330_tasklet() with CYCLIC_TRIGGER" because the list of 'done' xfers would be null yet. -- 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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