diff options
| -rw-r--r-- | Documentation/blackfin/00-INDEX | 5 | ||||
| -rw-r--r-- | Documentation/blackfin/bfin-spi-notes.txt | 14 |
2 files changed, 18 insertions, 1 deletions
diff --git a/Documentation/blackfin/00-INDEX b/Documentation/blackfin/00-INDEX index 10391d3e9b56..2df0365f2dff 100644 --- a/Documentation/blackfin/00-INDEX +++ b/Documentation/blackfin/00-INDEX @@ -1,5 +1,8 @@ 00-INDEX - This file -bfin-gpio-note.txt +bfin-gpio-notes.txt - Notes in developing/using bfin-gpio driver. + +bfin-spi-notes.txt + - Notes for using bfin spi bus driver. diff --git a/Documentation/blackfin/bfin-spi-notes.txt b/Documentation/blackfin/bfin-spi-notes.txt new file mode 100644 index 000000000000..556fa877f2e8 --- /dev/null +++ b/Documentation/blackfin/bfin-spi-notes.txt @@ -0,0 +1,14 @@ +SPI Chip Select behavior: + +With the Blackfin on-chip SPI peripheral, there is some logic tied to the CPHA +bit whether the Slave Select Line is controlled by hardware (CPHA=0) or +controlled by software (CPHA=1). However, the Linux SPI bus driver assumes that +the Slave Select is always under software control and being asserted during +the entire SPI transfer. - And not just bits_per_word duration. + +In most cases you can utilize SPI MODE_3 instead of MODE_0 to work-around this +behavior. If your SPI slave device in question requires SPI MODE_0 or MODE_2 +timing, you can utilize the GPIO controlled SPI Slave Select option instead. + +You can even use the same pin whose peripheral role is a SSEL, +but use it as a GPIO instead. |