diff options
| author | Lukas Wunner <lukas@wunner.de> | 2019-09-11 12:15:30 +0200 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2019-09-11 15:52:53 +0100 |
| commit | 4f2228cce2816e46dcac0be50a259a0311a90252 (patch) | |
| tree | a0cedf42f78838413fc044cf153a5ad7a91c6cdb /drivers/dma | |
| parent | 1513ceee70f2bd523e025efe0c715328e1a43ffd (diff) | |
| download | linux-4f2228cce2816e46dcac0be50a259a0311a90252.tar.bz2 | |
dmaengine: bcm2835: Allow cyclic transactions without interrupt
The BCM2835 DMA driver currently requests an interrupt from the
controller regardless whether or not the client has passed in the
DMA_PREP_INTERRUPT flag. This causes unnecessary overhead for cyclic
transactions which do not need an interrupt after each period.
We're about to add such a use case, namely cyclic clearing of the SPI
controller's RX FIFO, so amend the DMA driver to request an interrupt
only if DMA_PREP_INTERRUPT was passed in. Ignore the period_len for
such transactions and set it to the buffer length to make the driver's
calculations work.
Tested-by: Nuno Sá <nuno.sa@analog.com>
Tested-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Vinod Koul <vkoul@kernel.org>
Acked-by: Stefan Wahren <wahrenst@gmx.net>
Acked-by: Martin Sperl <kernel@martin.sperl.org>
Cc: Florian Kauer <florian.kauer@koalo.de>
Link: https://lore.kernel.org/r/73cf37be56eb4cbe6f696057c719f3a38cbaf26e.1568187525.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/dma')
| -rw-r--r-- | drivers/dma/bcm2835-dma.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c index 8101ff2f05c1..b40fb555b98b 100644 --- a/drivers/dma/bcm2835-dma.c +++ b/drivers/dma/bcm2835-dma.c @@ -691,7 +691,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic( struct bcm2835_desc *d; dma_addr_t src, dst; u32 info = BCM2835_DMA_WAIT_RESP; - u32 extra = BCM2835_DMA_INT_EN; + u32 extra = 0; size_t max_len = bcm2835_dma_max_frame_length(c); size_t frames; @@ -707,6 +707,11 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic( return NULL; } + if (flags & DMA_PREP_INTERRUPT) + extra |= BCM2835_DMA_INT_EN; + else + period_len = buf_len; + /* * warn if buf_len is not a multiple of period_len - this may leed * to unexpected latencies for interrupts and thus audiable clicks @@ -778,7 +783,10 @@ static int bcm2835_dma_terminate_all(struct dma_chan *chan) /* stop DMA activity */ if (c->desc) { - vchan_terminate_vdesc(&c->desc->vd); + if (c->desc->vd.tx.flags & DMA_PREP_INTERRUPT) + vchan_terminate_vdesc(&c->desc->vd); + else + vchan_vdesc_fini(&c->desc->vd); c->desc = NULL; bcm2835_dma_abort(c); } |