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authorLen Brown <len.brown@intel.com>2010-08-15 01:06:31 -0400
committerLen Brown <len.brown@intel.com>2010-08-15 01:06:31 -0400
commit95ee46aa8698f2000647dfb362400fadbb5807cf (patch)
treee5a05c7297f997e191c73091934e42e3195c0e40 /Documentation/blackfin/bfin-spi-notes.txt
parentcfa806f059801dbe7e435745eb2e187c8bfe1e7f (diff)
parent92fa5bd9a946b6e7aab6764e7312e4e3d9bed295 (diff)
downloadlinux-95ee46aa8698f2000647dfb362400fadbb5807cf.tar.bz2
Merge branch 'linus' into release
Conflicts: drivers/acpi/debug.c Signed-off-by: Len Brown <len.brown@intel.com>
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+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.