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| author | Mauro Carvalho Chehab <mchehab@infradead.org> | 2006-09-06 19:04:28 -0300 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@infradead.org> | 2006-09-06 19:04:28 -0300 |
| commit | 73417c50a08d93d5c209df8a49c8d0a0e0d0dc8b (patch) | |
| tree | 74414bebe3d0e21fb3e0d00b183d74cf876c5e0c /linux/Documentation | |
| parent | 9f9d0d9c21ed8c31ec1672eeb262502af5b1e326 (diff) | |
| download | mediapointer-dvb-s2-73417c50a08d93d5c209df8a49c8d0a0e0d0dc8b.tar.gz mediapointer-dvb-s2-73417c50a08d93d5c209df8a49c8d0a0e0d0dc8b.tar.bz2 | |
Improved i2c performance on software bitbang algoritm
From: Mauro Carvalho Chehab <mchehab@infradead.org>
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 <khali@linux-fr.org> for pointing this improvement.
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Diffstat (limited to 'linux/Documentation')
| -rw-r--r-- | linux/Documentation/video4linux/bttv/Insmod-options | 6 |
1 files changed, 6 insertions, 0 deletions
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= |