[U-Boot] [PATCH] i2c: mvtwsi: Fix problem with baud rate calculation

[Stefan Roese]

The current implementation for baudrate calculation is incorrect.
This part from the formula:

"2 ^ (n + 1)" is not equivalent to (1 << n) but to (2 << n)!

This patch fixes this and moves this calculation to a function instead of using a macro.
This new function is taken from the Linux kernel.

This was detected and tested on the Marvell Armada A38x DB-88F6820-GP eval board.

Signed-off-by: Stefan Roese <sr at denx.de>
Cc: Prafulla Wadaskar <prafulla at marvell.com>
Cc: Luka Perkov <luka.perkov at sartura.hr>
Cc: Hans de Goede <hdegoede at redhat.com>
Cc: Ian Campbell <ijc at hellion.org.uk>
Cc: Heiko Schocher <hs at denx.de>
---
 drivers/i2c/mvtwsi.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/mvtwsi.c b/drivers/i2c/mvtwsi.c
index 9b2ca1e..320235c 100644
--- a/drivers/i2c/mvtwsi.c
+++ b/drivers/i2c/mvtwsi.c
@@ -228,13 +228,10 @@ static int twsi_stop(int status)
 	return status;
 }
 
-/*
- * Ugly formula to convert m and n values to a frequency comes from
- * TWSI specifications
- */
-
-#define TWSI_FREQUENCY(m, n) \
-	(CONFIG_SYS_TCLK / (10 * (m + 1) * (1 << n)))
+static unsigned int twsi_calc_freq(const int n, const int m)
+{
+	return CONFIG_SYS_TCLK / (10 * (m + 1) * (2 << n));
+}
 
 /*
  * Reset controller.
@@ -266,7 +263,7 @@ static unsigned int twsi_i2c_set_bus_speed(struct i2c_adapter *adap,
 	/* compute m, n setting for highest speed not above requested speed */
 	for (n = 0; n < 8; n++) {
 		for (m = 0; m < 16; m++) {
-			tmp_speed = TWSI_FREQUENCY(m, n);
+			tmp_speed = twsi_calc_freq(n, m);
 			if ((tmp_speed <= requested_speed)
 			 && (tmp_speed > highest_speed)) {
 				highest_speed = tmp_speed;
-- 
2.3.3