From 84bf2c868f3ca996e5bbd3beb2ef502f457140f3 Mon Sep 17 00:00:00 2001 From: Aaro Koskinen Date: Wed, 27 May 2009 17:54:46 +0300 Subject: [PATCH] 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 Acked-by: Tony Lindgren Signed-off-by: Ben Dooks --- drivers/i2c/busses/i2c-omap.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c index a879e4b..c73475d 100644 --- 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 */ -- 2.7.4