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| author | Frode Isaksen <fisaksen@baylibre.com> | 2017-03-17 16:41:10 +0100 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2017-03-17 22:00:51 +0000 |
| commit | 1234e8398fe03267bf2e353e36825dbd0abc2fc6 (patch) | |
| tree | 6ecedf5fbb11175762f7506032ed33dce32e40da /drivers/spi/spi-davinci.c | |
| parent | 4dd9becbce4f10009322c3e2297f9db3ace94a10 (diff) | |
| download | linux-1234e8398fe03267bf2e353e36825dbd0abc2fc6.tar.gz linux-1234e8398fe03267bf2e353e36825dbd0abc2fc6.tar.bz2 linux-1234e8398fe03267bf2e353e36825dbd0abc2fc6.zip | |
spi: davinci: add comment about dummy tx buffer usage
Add explanation about using the the rx buffer as the
dummy tx buffer.
Signed-off-by: Frode Isaksen <fisaksen@baylibre.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi/spi-davinci.c')
| -rw-r--r-- | drivers/spi/spi-davinci.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c index f37bbdd18d61..595acdcfc7d0 100644 --- a/drivers/spi/spi-davinci.c +++ b/drivers/spi/spi-davinci.c @@ -660,7 +660,11 @@ static int davinci_spi_bufs(struct spi_device *spi, struct spi_transfer *t) goto err_desc; if (!t->tx_buf) { - /* use rx buffer as dummy tx buffer */ + /* To avoid errors when doing rx-only transfers with + * many SG entries (> 20), use the rx buffer as the + * dummy tx buffer so that dma reloads are done at the + * same time for rx and tx. + */ t->tx_sg.sgl = t->rx_sg.sgl; t->tx_sg.nents = t->rx_sg.nents; } |