i2c: mvtwsi: Fix problem with baud rate calculation

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@denx.de>
Cc: Prafulla Wadaskar <prafulla@marvell.com>
Cc: Luka Perkov <luka.perkov@sartura.hr>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Ian Campbell <ijc@hellion.org.uk>
Cc: Heiko Schocher <hs@denx.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>

diff --git a/drivers/i2c/mvtwsi.c b/drivers/i2c/mvtwsi.c
index 9b2ca1e81ba33a7f94e539a020336015b30592fa..6f6edd5e519547a8f201facab1da48d2a9fa07d6 100644 (file)
--- a/drivers/i2c/mvtwsi.c
+++ b/drivers/i2c/mvtwsi.c
@@ -228,13 +228,14 @@ 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)
+{
+#ifdef CONFIG_SUNXI
+       return CONFIG_SYS_TCLK / (10 * (m + 1) * (1 << n));
+#else
+       return CONFIG_SYS_TCLK / (10 * (m + 1) * (2 << n));
+#endif
+}
 
 /*
  * Reset controller.
@@ -266,7 +267,7 @@ 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;