| Message ID | 037b83d2ae8aa92448b9d647436012c06f4c0561.1564825752.git.lukas@wunner.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | Raspberry Pi SPI speedups | expand |
On 03-08-19, 12:10, Lukas Wunner wrote: > 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. Acked-by: Vinod Koul <vkoul@kernel.org> > > Tested-by: Nuno Sá <nuno.sa@analog.com> > Signed-off-by: Lukas Wunner <lukas@wunner.de> > Cc: Martin Sperl <kernel@martin.sperl.org> > Cc: Florian Kauer <florian.kauer@koalo.de> > --- > drivers/dma/bcm2835-dma.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c > index 523c507ad69e..a65514fcb7f2 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); > } > -- > 2.20.1
diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c index 523c507ad69e..a65514fcb7f2 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); }