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authorAaro Koskinen <aaro.koskinen@nokia.com>2009-05-27 17:54:45 +0300
committerBen Dooks <ben-linux@fluff.org>2009-06-13 10:39:25 +0100
commitbaf46b4e378d7950dff7ba30cfd50ff585987cb4 (patch)
tree571bd77cb953d1fc6a206c250b3cf8dd4718546f /drivers/i2c
parente0cd2dd5dd2b7c6512e46ce0b4f119cd7b0c74a4 (diff)
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i2c: OMAP2/3: Fix scll/sclh calculations
Fix scll/sclh calculations for HS and fast modes. Currently the driver uses equal (roughly) low/high times which will result in too short low time. OMAP3430 TRM gives the following equations: F/S: tLow = (scll + 7) * internal_clk tHigh = (sclh + 5) * internal_clk HS: tLow = (scll + 7) * fclk tHigh = (sclh + 5) * fclk Furthermore, the I2C specification sets the following minimum values for HS tLow/tHigh for capacitive bus loads 100 pF (maximum speed 3400) and 400 pF (maximum speed 1700): speed tLow tHigh 3400 160 ns 60 ns 1700 320 ns 120 ns and for F/S: speed tLow tHigh 400 1300 ns 600 ns 100 4700 ns 4000 ns By using duty cycles 33/66 (HS, F) and 50/50 (S) we stay above these minimum values. Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com> Acked-by: Tony Lindgren <tony@atomide.com> Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/busses/i2c-omap.c25
1 files changed, 18 insertions, 7 deletions
diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index ece0125..a879e4b 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -343,17 +343,28 @@ static int omap_i2c_init(struct omap_i2c_dev *dev)
/* If configured for High Speed */
if (dev->speed > 400) {
+ unsigned long scl;
+
/* For first phase of HS mode */
- fsscll = internal_clk / (400 * 2) - 6;
- fssclh = internal_clk / (400 * 2) - 6;
+ scl = internal_clk / 400;
+ fsscll = scl - (scl / 3) - 7;
+ fssclh = (scl / 3) - 5;
/* For second phase of HS mode */
- hsscll = fclk_rate / (dev->speed * 2) - 6;
- hssclh = fclk_rate / (dev->speed * 2) - 6;
+ scl = fclk_rate / dev->speed;
+ hsscll = scl - (scl / 3) - 7;
+ hssclh = (scl / 3) - 5;
+ } else if (dev->speed > 100) {
+ unsigned long scl;
+
+ /* Fast mode */
+ scl = internal_clk / dev->speed;
+ fsscll = scl - (scl / 3) - 7;
+ fssclh = (scl / 3) - 5;
} else {
- /* To handle F/S modes */
- fsscll = internal_clk / (dev->speed * 2) - 6;
- fssclh = internal_clk / (dev->speed * 2) - 6;
+ /* Standard mode */
+ fsscll = internal_clk / (dev->speed * 2) - 7;
+ fssclh = internal_clk / (dev->speed * 2) - 5;
}
scll = (hsscll << OMAP_I2C_SCLL_HSSCLL) | fsscll;
sclh = (hssclh << OMAP_I2C_SCLH_HSSCLH) | fssclh;