Blackfin: make baud calculation more accurate

We should use the algorithm in the Linux kernel so that the UART divisor
calculation is more accurate.  It also fixes problems on some picky UARTs
that have sampling anomalies.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

cpu/blackfin/serial.h

@@ -175,11 +175,11 @@ static inline uint32_t serial_early_get_baud(void)
 __attribute__((always_inline))
 static inline void serial_early_set_baud(uint32_t baud)
 {
-	/* Translate from baud into divisor in terms of SCLK.
-	 * The +1 is to make sure we over sample just a little
-	 * rather than under sample the incoming signals.
+	/* Translate from baud into divisor in terms of SCLK.  The
+	 * weird multiplication is to make sure we over sample just
+	 * a little rather than under sample the incoming signals.
 	 */
-	uint16_t divisor = (get_sclk() / (baud * 16)) + 1;
+	uint16_t divisor = (get_sclk() + (baud * 8)) / (baud * 16) - ANOMALY_05000230;
 
 	/* Set DLAB in LCR to Access DLL and DLH */
 	ACCESS_LATCH();