[PATCH 3.13.y-ckt 092/138] dmaengine: dw: disable BLOCK IRQs for non-cyclic xfer

From: Kamal Mostafa
Date: Wed Mar 09 2016 - 18:34:36 EST


3.13.11-ckt36 -stable review patch. If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>

commit ee1cdcdae59563535485a5f56ee72c894ab7d7ad upstream.

The commit 2895b2cad6e7 ("dmaengine: dw: fix cyclic transfer callbacks")
re-enabled BLOCK interrupts with regard to make cyclic transfers work. However,
this change becomes a regression for non-cyclic transfers as interrupt counters
under stress test had been grown enormously (approximately per 4-5 bytes in the
UART loop back test).

Taking into consideration above enable BLOCK interrupts if and only if channel
is programmed to perform cyclic transfer.

Fixes: 2895b2cad6e7 ("dmaengine: dw: fix cyclic transfer callbacks")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Acked-by: Mans Rullgard <mans@xxxxxxxxx>
Tested-by: Mans Rullgard <mans@xxxxxxxxx>
Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Signed-off-by: Vinod Koul <vinod.koul@xxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
drivers/dma/dw/core.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 029a086..618653f 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -169,7 +169,6 @@ static void dwc_initialize(struct dw_dma_chan *dwc)

/* Enable interrupts */
channel_set_bit(dw, MASK.XFER, dwc->mask);
- channel_set_bit(dw, MASK.BLOCK, dwc->mask);
channel_set_bit(dw, MASK.ERROR, dwc->mask);

dwc->initialized = true;
@@ -593,6 +592,9 @@ static void dwc_handle_cyclic(struct dw_dma *dw, struct dw_dma_chan *dwc,

spin_unlock_irqrestore(&dwc->lock, flags);
}
+
+ /* Re-enable interrupts */
+ channel_set_bit(dw, MASK.BLOCK, dwc->mask);
}

/* ------------------------------------------------------------------------- */
@@ -623,11 +625,8 @@ static void dw_dma_tasklet(unsigned long data)
dwc_scan_descriptors(dw, dwc);
}

- /*
- * Re-enable interrupts.
- */
+ /* Re-enable interrupts */
channel_set_bit(dw, MASK.XFER, dw->all_chan_mask);
- channel_set_bit(dw, MASK.BLOCK, dw->all_chan_mask);
channel_set_bit(dw, MASK.ERROR, dw->all_chan_mask);
}

@@ -1219,6 +1218,7 @@ static void dwc_free_chan_resources(struct dma_chan *chan)
int dw_dma_cyclic_start(struct dma_chan *chan)
{
struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
+ struct dw_dma *dw = to_dw_dma(chan->device);
unsigned long flags;

if (!test_bit(DW_DMA_IS_CYCLIC, &dwc->flags)) {
@@ -1227,7 +1227,12 @@ int dw_dma_cyclic_start(struct dma_chan *chan)
}

spin_lock_irqsave(&dwc->lock, flags);
+
+ /* Enable interrupts to perform cyclic transfer */
+ channel_set_bit(dw, MASK.BLOCK, dwc->mask);
+
dwc_dostart(dwc, dwc->cdesc->desc[0]);
+
spin_unlock_irqrestore(&dwc->lock, flags);

return 0;
--
2.7.0