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 --- 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;