Dne So 15. května 2010 22:48:17 Robert Jarzmik napsal(a): > Marek Vasut <marek.vasut@xxxxxxxxx> writes: > > Dne So 15. května 2010 00:03:45 Jeff Garzik napsal(a): > >> On 05/09/2010 11:02 PM, Marek Vasut wrote: > >> > This patch adds a driver for a harddrive attached to PXA address and > >> > data bus. Unlike pata_platform, this driver allows usage of PXA DMA > >> > controller, making the transmission speed 3x higher. > > ... > zip > ... > > >> > +static void pxa_bmdma_setup(struct ata_queued_cmd *qc) > >> > +{ > >> > + struct pata_pxa_data *pd = qc->ap->private_data; > >> > + int si = 0; > >> > + struct scatterlist *sg; > >> > + > >> > + pd->dma_desc_id = 0; > >> > + > >> > + DCSR(pd->dma_channel) = 0; > >> > + DALGN&= ~(1<< pd->dma_dreq); > >> > + > >> > + for_each_sg(qc->sg, sg, qc->n_elem, si) > >> > + pxa_load_dmac(sg, qc); > >> > + > >> > + pd->dma_desc[pd->dma_desc_id - 1].ddadr = DDADR_STOP; > >> > + > >> > + /* Fire IRQ only at the end of last block */ > >> > + pd->dma_desc[pd->dma_desc_id - 1].dcmd |= DCMD_ENDIRQEN; > >> > + > >> > + DDADR(pd->dma_channel) = pd->dma_desc_addr; > >> > + DRCMR(pd->dma_dreq) = DRCMR_MAPVLD | pd->dma_channel; > >> > + qc->ap->ops->sff_exec_command(qc->ap,&qc->tf); > >> > +} > > I don't know the ATA infrastructure well here, but I wonder how cache > consistency is handled here. Normally, once the sg is ready, you have to > call dma_map_sg() to map the scatter/gather _and_ to flush any stale cache > entry the CPU(s) might have over the memory used for the transfer. > > Once the transfer is over, you have to call dma_unmap_sg() to give back the > memory (ie. ensure cache consistency once the peripheral has finished > pushing data to the memory). This should be taken care of by the libata code, shouldn't it ? > > I didn't see that is this piece of code. Did I miss something ? > > > BUG() doesn't happen here so the user won't come into any contact with it > > unless he sets the drive on fire or something. And in case user comes in > > contact with it, this is all I need to know to help him. Or maybe > > dev_err() would be good here ? > > > >> > + * Read DMA status. The bmdma_stop() will take care of properly > >> > finishing the + * DMA transfer so we always have DMA-complete > >> > interrupt here. > >> > + */ > >> > +static unsigned char pxa_bmdma_status(struct ata_port *ap) > >> > +{ > >> > + return ATA_DMA_INTR; > >> > +} > >> > >> are you able to detect bus error? > > > > Sadly, no. Nor can I detect any other condition. > > Wouldn't the DCSR_BUSERR bit of DCSR report a bus error ? I have doubts, check the PXA270 TRM for example for description of that bit. > > +/* > + * DMA interrupt handler. > + */ > +static void pxa_ata_dma_irq(int dma, void *port) > +{ > + uint32_t dcsr; > + struct ata_port *ap = port; > + struct pata_pxa_data *pd = ap->private_data; > + > + dcsr = DCSR(dma); > + DCSR(dma) = dcsr; > + if (dcsr & DCSR_STOPSTATE) > + complete(&pd->dma_done); > +} > > Cheers. > > -- > Robert -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html