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| author | Mauro Carvalho Chehab <mchehab@infradead.org> | 2006-09-07 02:04:28 +0400 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@infradead.org> | 2006-09-26 19:30:35 +0400 |
| commit | 141276b57e1f83a86b8e77554b36511be0a7049c (patch) | |
| tree | fe0e93f7eeaca9ba6b06bd74bf6758b8a1986b94 /Documentation/video4linux/bttv | |
| parent | 48c06d5e2d63c1d6282c0f7fe67741a39d6c1852 (diff) | |
| download | linux-141276b57e1f83a86b8e77554b36511be0a7049c.tar.xz | |
V4L/DVB (4609): Improved i2c performance on software bitbang algoritm
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 'Documentation/video4linux/bttv')
| -rw-r--r-- | Documentation/video4linux/bttv/Insmod-options | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/video4linux/bttv/Insmod-options b/Documentation/video4linux/bttv/Insmod-options index fc94ff235ffa..bb7c2cac7917 100644 --- a/Documentation/video4linux/bttv/Insmod-options +++ b/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= |