i2c: OMAP3: Better noise suppression for fast/standard modes

Use longer noise filter period for fast and standard mode. Based on an
earlier patch by Eero Nurkkala.

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>

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index a879e4bf5122e80f2c5424f37101cde3ec2c6843..c73475dd0fba00c2dd5953b3b37ebf5837ad7f37 100644 (file)
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -333,8 +333,18 @@ static int omap_i2c_init(struct omap_i2c_dev *dev)
 
        if (cpu_is_omap2430() || cpu_is_omap34xx()) {
 
-               /* HSI2C controller internal clk rate should be 19.2 Mhz */
-               internal_clk = 19200;
+               /*
+                * HSI2C controller internal clk rate should be 19.2 Mhz for
+                * HS and for all modes on 2430. On 34xx we can use lower rate
+                * to get longer filter period for better noise suppression.
+                * The filter is iclk (fclk for HS) period.
+                */
+               if (dev->speed > 400 || cpu_is_omap_2430())
+                       internal_clk = 19200;
+               else if (dev->speed > 100)
+                       internal_clk = 9600;
+               else
+                       internal_clk = 4000;
                fclk_rate = clk_get_rate(dev->fclk) / 1000;
 
                /* Compute prescaler divisor */