From 73417c50a08d93d5c209df8a49c8d0a0e0d0dc8b Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Wed, 6 Sep 2006 19:04:28 -0300 Subject: Improved i2c performance on software bitbang algoritm From: Mauro Carvalho Chehab Software I2C were using a very conservative value of udelay=16, meaning about 20Kbps. According with Philips I2C datasheet, the i2c should answer well for times at the order of 4.7 us. So, using udelay=5 should work for all devices. After this patch, the speed should be close to 66,67 Kbps, with the current kernel software bitbang, with 30/60 duty cycle. Anyway, added a new parameter (i2c_udelay) that would allow using conservative values, if eventually a hardware doesn't support the datasheet values. Thanks to Jean Delvare for pointing this improvement. Signed-off-by: Mauro Carvalho Chehab --- linux/Documentation/video4linux/bttv/Insmod-options | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'linux/Documentation/video4linux/bttv') diff --git a/linux/Documentation/video4linux/bttv/Insmod-options b/linux/Documentation/video4linux/bttv/Insmod-options index fc94ff235..bb7c2cac7 100644 --- a/linux/Documentation/video4linux/bttv/Insmod-options +++ b/linux/Documentation/video4linux/bttv/Insmod-options @@ -54,6 +54,12 @@ bttv.o dropouts. chroma_agc=0/1 AGC of chroma signal, off by default. adc_crush=0/1 Luminance ADC crush, on by default. + i2c_udelay= Allow reduce I2C speed. Default is 5 usecs + (meaning 66,67 Kbps). The default is the + maximum supported speed by kernel bitbang + algoritm. You may use lower numbers, if I2C + messages are lost (16 is known to work on + all supported cards). bttv_gpio=0/1 gpiomask= -- cgit v1.2.3