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>
diff --git a/cpu/blackfin/serial.h b/cpu/blackfin/serial.h
index 1f0f4b4..ec40c26 100644
--- a/cpu/blackfin/serial.h
+++ b/cpu/blackfin/serial.h
@@ -175,11 +175,11 @@
__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();