Blackfin SPI Driver: Fix erroneous SPI Clock divisor calculation

Fix erroneous SPI Clock divisor calculation.  Make sure SPI_BAUD is always
>= 2.  Writing a value of 0 or 1 to the SPI_BAUD register disables the
serial clock.
Signed-off-by: NMichael Hennerich <michael.hennerich@analog.com>
Signed-off-by: NBryan Wu <cooloney@kernel.org>
Acked-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/blackfin/include/asm/bfin5xx_spi.h

@@ -11,6 +11,8 @@
 #ifndef _SPI_CHANNEL_H_
 #define _SPI_CHANNEL_H_
 
+#define MIN_SPI_BAUD_VAL	2
+
 #define SPI_READ              0
 #define SPI_WRITE             1
 

drivers/spi/spi_bfin5xx.c

@@ -158,6 +158,9 @@ static u16 hz_to_spi_baud(u32 speed_hz)
 	if ((sclk % (2 * speed_hz)) > 0)
 		spi_baud++;
 
+	if (spi_baud < MIN_SPI_BAUD_VAL)
+		spi_baud = MIN_SPI_BAUD_VAL;
+
 	return spi_baud;
 }