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i2c: mvtwsi: Fix problem with baud rate calculation

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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>
This commit is contained in:
Stefan Roese 2015-03-18 09:30:54 +01:00 committed by Heiko Schocher
parent e6fbc3e4f1
commit f582a1583b
1 changed files with 9 additions and 8 deletions
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17
drivers/i2c/mvtwsi.c
View file

@ -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;