On Mon, Jun 06, 2016 at 10:33:18AM -0700, Eric Anholt wrote: > Vinod Koul <vinod.koul@xxxxxxxxx> writes: > > > On Fri, Jun 03, 2016 at 07:29:11PM -0700, Eric Anholt wrote: > >> The tx_status hook is supposed to be safe to call from interrupt > >> context, but it wouldn't ever return completion for the last transfer, > >> meaning you couldn't poll for DMA completion with interrupts masked. > > > > and why is that? > > Maybe this was poorly worded. How about: > > The tx_status hook is supposed to be safe to call from interrupt > context. However, the current transfer currently only gets marked > complete by the IRQ handler, so if interrupts were masked then polling > for completion would never finish. Sound better :) > > >> This fixes IRQ handling for bcm2835's DSI1, which requires using the > >> DMA engine to write its registers due to a bug in the AXI bridge. > >> > >> Signed-off-by: Eric Anholt <eric@xxxxxxxxxx> > >> --- > >> drivers/dma/bcm2835-dma.c | 24 +++++++++++++++++++----- > >> 1 file changed, 19 insertions(+), 5 deletions(-) > >> > >> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c > >> index 6149b27c33ad..320461c578e3 100644 > >> --- a/drivers/dma/bcm2835-dma.c > >> +++ b/drivers/dma/bcm2835-dma.c > >> @@ -570,16 +570,16 @@ static enum dma_status bcm2835_dma_tx_status(struct dma_chan *chan, > >> struct virt_dma_desc *vd; > >> enum dma_status ret; > >> unsigned long flags; > >> + u32 residue; > >> > >> ret = dma_cookie_status(chan, cookie, txstate); > >> - if (ret == DMA_COMPLETE || !txstate) > >> + if (ret == DMA_COMPLETE) > > > > Why do you change this? txstate can be NULL, so no point calculating reside > > for those cases > > The point was to go into the "Calculate where we're at in our current > DMA (if the current DMA is the one we're asking about status for)" path, > so that we could note when the DMA is complete even when there's no > txstate passed in. Can you explain what you mean by current DMA! The claulation is always done for 'descriptor' represnted by the cookie. So it doesnt not matter...! Thanks -- ~Vinod
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