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.