Vinod Koul <vinod.koul@xxxxxxxxx> writes: > 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...! By current I mean the current descriptor that has been submitted to the hardware, in bcm2835_chan->desc.
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