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>
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
index b7bb07c..0d8c975 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);