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V4L/DVB (4609): Improved i2c performance on software bitbang algoritm

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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>
This commit is contained in:
Mauro Carvalho Chehab
2006-09-06 19:04:28 -03:00
parent 48c06d5e2d
commit 141276b57e
3 changed files with 32 additions and 0 deletions
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6
Documentation/video4linux/bttv/Insmod-options
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@@ -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=