| Message ID | 1443559488-2416-4-git-send-email-hamzahfrq.sub@gmail.com (mailing list archive) |
|---|---|
| State | Under Review |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
On Tue, Sep 29, 2015 at 10:44:45PM +0200, hamzahfrq.sub@gmail.com wrote: > From: Muhammad Hamza Farooq <mfarooq@visteon.com> > > At high speeds, DMA interrupts come very fast. If there's an interrupt > pending before previous is handled, this method can help return actual which method ?? > status of the DMA transaction by reading the hardware flag
Hi Muhammad, Thank you for the patch. On Tuesday 29 September 2015 22:44:45 hamzahfrq.sub@gmail.com wrote: > From: Muhammad Hamza Farooq <mfarooq@visteon.com> > > At high speeds, DMA interrupts come very fast. If there's an interrupt > pending before previous is handled, this method can help return actual > status of the DMA transaction by reading the hardware flag > > Signed-off-by: Muhammad Hamza Farooq <mfarooq@visteon.com> > --- > drivers/dma/sh/rcar-dmac.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c > index c7cd4ed..6c806d0 100644 > --- a/drivers/dma/sh/rcar-dmac.c > +++ b/drivers/dma/sh/rcar-dmac.c > @@ -314,6 +314,14 @@ static bool rcar_dmac_chan_is_busy(struct > rcar_dmac_chan *chan) return (chcr & (RCAR_DMACHCR_DE | RCAR_DMACHCR_TE)) > == RCAR_DMACHCR_DE; } > > +/* Transfer completed but not yet handled */ > +static bool rcar_dmac_last_tx_complete(struct rcar_dmac_chan *chan) > +{ > + u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR); > + > + return (chcr & RCAR_DMACHCR_TE) == RCAR_DMACHCR_TE; > +} > + > static void rcar_dmac_chan_start_xfer(struct rcar_dmac_chan *chan) > { > struct rcar_dmac_desc *desc = chan->desc.running; > @@ -1238,6 +1246,10 @@ static enum dma_status rcar_dmac_tx_status(struct > dma_chan *chan, unsigned long flags; > unsigned int residue; > > + /* Interrupt not yet serviced */ > + if (rcar_dmac_last_tx_complete(rchan)) > + return DMA_COMPLETE; > + I don't think this will work. In particular rcar_dmac_tx_status() can be called with a cookie corresponding to a transfer not yet scheduled. A pending transfer complete interrupt doesn't mean that that cookie is complete. Furthermore I'm not sure this will really improve performances. The dma_cookie_status() call below just compares cookie values, I don't expect it to be much slower than a register read. > status = dma_cookie_status(chan, cookie, txstate); > if (status == DMA_COMPLETE || !txstate) > return status;
diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c index c7cd4ed..6c806d0 100644 --- a/drivers/dma/sh/rcar-dmac.c +++ b/drivers/dma/sh/rcar-dmac.c @@ -314,6 +314,14 @@ static bool rcar_dmac_chan_is_busy(struct rcar_dmac_chan *chan) return (chcr & (RCAR_DMACHCR_DE | RCAR_DMACHCR_TE)) == RCAR_DMACHCR_DE; } +/* Transfer completed but not yet handled */ +static bool rcar_dmac_last_tx_complete(struct rcar_dmac_chan *chan) +{ + u32 chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR); + + return (chcr & RCAR_DMACHCR_TE) == RCAR_DMACHCR_TE; +} + static void rcar_dmac_chan_start_xfer(struct rcar_dmac_chan *chan) { struct rcar_dmac_desc *desc = chan->desc.running; @@ -1238,6 +1246,10 @@ static enum dma_status rcar_dmac_tx_status(struct dma_chan *chan, unsigned long flags; unsigned int residue; + /* Interrupt not yet serviced */ + if (rcar_dmac_last_tx_complete(rchan)) + return DMA_COMPLETE; + status = dma_cookie_status(chan, cookie, txstate); if (status == DMA_COMPLETE || !txstate) return status;