summaryrefslogtreecommitdiff
path: root/drivers/spi/spi-bcm2835.c
diff options
context:
space:
mode:
authorMartin Sperl <kernel@martin.sperl.org>2019-04-23 23:15:10 +0300
committerMark Brown <broonie@kernel.org>2019-05-08 11:58:54 +0300
commitc41d62b06cb92289ab5db9d37a0f27fe6271fa34 (patch)
treea8fed8e77108b175647dc2c740746f5c4f0bf4da /drivers/spi/spi-bcm2835.c
parent7f1922eb3adba8c372fdf0d04fe9e6268f98291a (diff)
downloadlinux-c41d62b06cb92289ab5db9d37a0f27fe6271fa34.tar.xz
spi: bcm2835: added comment about different bus behaviour of DMA mode
The DMA mode behaves slightly different than polling or interrupt driven mode, so just document the fact Signed-off-by: Martin Sperl <kernel@martin.sperl.org> Changelog: V1 -> V2: applied feedback by Stefan Wahren new in V2 Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi/spi-bcm2835.c')
-rw-r--r--drivers/spi/spi-bcm2835.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index b7bb07c9507d..0d8c97502f14 100644
--- a/drivers/spi/spi-bcm2835.c
+++ b/drivers/spi/spi-bcm2835.c
@@ -800,7 +800,10 @@ static int bcm2835_spi_transfer_one(struct spi_master *master,
if (tfr->len < spi_used_hz / HZ_PER_BYTE)
return bcm2835_spi_transfer_one_poll(master, spi, tfr, cs);
- /* run in dma mode if conditions are right */
+ /* run in dma mode if conditions are right
+ * Note that unlike poll or interrupt mode DMA mode does not have
+ * this 1 idle clock cycle pattern but runs the spi clock without gaps
+ */
if (master->can_dma && bcm2835_spi_can_dma(master, spi, tfr))
return bcm2835_spi_transfer_one_dma(master, spi, tfr, cs);