From f582a1583b2c7ae91737f3b1a0b850e7f4ef68bb Mon Sep 17 00:00:00 2001
From: Stefan Roese <sr@denx.de>
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 <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>
---
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;
--
2.39.5