From f582a1583b2c7ae91737f3b1a0b850e7f4ef68bb Mon Sep 17 00:00:00 2001 From: Stefan Roese Date: Wed, 18 Mar 2015 09:30:54 +0100 Subject: [PATCH] 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 Cc: Prafulla Wadaskar Cc: Luka Perkov Cc: Hans de Goede Cc: Ian Campbell Cc: Heiko Schocher Acked-by: Hans de Goede --- drivers/i2c/mvtwsi.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/drivers/i2c/mvtwsi.c b/drivers/i2c/mvtwsi.c index 9b2ca1e81b..6f6edd5e51 100644 --- 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; -- 2.25.1