From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaro Koskinen Subject: [PATCH 2/2] I2C: OMAP3: Better noise suppression for fast/standard modes Date: Wed, 27 May 2009 17:54:46 +0300 Message-ID: <1243436086-3623-2-git-send-email-aaro.koskinen@nokia.com> References: <> <1243436086-3623-1-git-send-email-aaro.koskinen@nokia.com> Return-path: In-Reply-To: <1243436086-3623-1-git-send-email-aaro.koskinen-xNZwKgViW5gAvxtiuMwx3w@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-i2c@vger.kernel.org Use longer noise filter period for fast and standard mode. Based on an earlier patch by Eero Nurkkala. Signed-off-by: Aaro Koskinen --- drivers/i2c/busses/i2c-omap.c | 14 ++++++++++++-- 1 files changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c index 5d9880c..8c76cea 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 */ -- 1.5.4.3