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).
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 ?
+/*
+ * 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
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