On Wed, Dec 10, 2014 at 11:55:18AM +0100, Robert Baldyga wrote: > DMA_PAUSE command is used for halting DMA transfer on chosen channel. > It can be useful when we want to safely read residue before terminating > all requests on channel. Otherwise there can be situation when some data > is transferred before channel termination but after reading residue, > which obviously results with data loss. To avoid this situation we can > pause channel, read residue and then terminate all requests. > This scenario is common, for example, in serial port drivers. And where is the resume here? Also this needs rebase -- ~Vinod > > Signed-off-by: Robert Baldyga <r.baldyga@xxxxxxxxxxx> > --- > drivers/dma/pl330.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c > index 2f4d561..ead4369 100644 > --- a/drivers/dma/pl330.c > +++ b/drivers/dma/pl330.c > @@ -2137,6 +2137,25 @@ static int pl330_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd, unsigned > pm_runtime_mark_last_busy(pl330->ddma.dev); > pm_runtime_put_autosuspend(pl330->ddma.dev); > break; > + case DMA_PAUSE: > + /* > + * We don't support DMA_RESUME command because of hardware > + * limitations, so after pausing the channel we cannot restore > + * it to active state. We have to terminate channel and setup > + * DMA transfer again. This pause feature was implemented to > + * allow safely read residue before channel termination. > + */ > + pm_runtime_get_sync(pl330->ddma.dev); > + spin_lock_irqsave(&pch->lock, flags); > + > + spin_lock(&pl330->lock); > + _stop(pch->thread); > + spin_unlock(&pl330->lock); > + > + spin_unlock_irqrestore(&pch->lock, flags); > + pm_runtime_mark_last_busy(pl330->ddma.dev); > + pm_runtime_put_autosuspend(pl330->ddma.dev); > + break; > case DMA_SLAVE_CONFIG: > slave_config = (struct dma_slave_config *)arg; > > -- > 1.9.1 > -- -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
