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authorMichal Marek <mmarek@suse.cz>2010-10-12 15:09:06 +0200
committerMichal Marek <mmarek@suse.cz>2010-10-12 15:09:06 +0200
commit239060b93bb30a4ad55f1ecaa512464a035cc5ba (patch)
tree77f79810e57d4fc24356eca0cd6db463e8994128 /Documentation/blackfin/bfin-spi-notes.txt
parent1408b15b98635a13bad2e2a50b3c2ae2ccdf625b (diff)
parente9203c988234aa512bd45ca32b52e21c7bbfc414 (diff)
downloadop-kernel-dev-239060b93bb30a4ad55f1ecaa512464a035cc5ba.zip
op-kernel-dev-239060b93bb30a4ad55f1ecaa512464a035cc5ba.tar.gz
Merge branch 'kbuild/rc-fixes' into kbuild/kconfig
We need to revert the temporary hack in 71ebc01, hence the merge.
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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.
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