spi_mpc83xx.c underclocking hotfix
The MPC83xx SPI controller clock divider can divide the system clock by not more then 1024. The spi_mpc83xx driver does not check this and silently writes garbage to the SPI controller registers when asked to run at lower frequencies. I've tried to run the SPI on a 266MHz MPC8349E with 100kHz for debugging a bus problem and suddenly was confronted with a 2nd problem to debug.. ;-) The patch adds an additional check which avoids writing garbage to the SPI controller registers and warn the user about it. This might help others to avoid simmilar problems. Cc: Kumar Gala <galak@gate.crashing.org> Cc: David Brownell <david-b@pacbell.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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