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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> | 2006-09-26 12:30:35 -0300 |
| commit | 141276b57e1f83a86b8e77554b36511be0a7049c (patch) | |
| tree | fe0e93f7eeaca9ba6b06bd74bf6758b8a1986b94 /drivers/media/video/bt8xx/bttv-i2c.c | |
| parent | V4L/DVB (4608a): V4L1 API conversion not finished yet (diff) | |
| download | linux-dev-141276b57e1f83a86b8e77554b36511be0a7049c.tar.xz linux-dev-141276b57e1f83a86b8e77554b36511be0a7049c.zip | |
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 'drivers/media/video/bt8xx/bttv-i2c.c')
| -rw-r--r-- | drivers/media/video/bt8xx/bttv-i2c.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/media/video/bt8xx/bttv-i2c.c b/drivers/media/video/bt8xx/bttv-i2c.c index 4b562b386fcf..03ee170181f2 100644 --- a/drivers/media/video/bt8xx/bttv-i2c.c +++ b/drivers/media/video/bt8xx/bttv-i2c.c @@ -8,6 +8,9 @@ & Marcus Metzler (mocm@thp.uni-koeln.de) (c) 1999-2003 Gerd Knorr <kraxel@bytesex.org> + (c) 2005 Mauro Carvalho Chehab <mchehab@infradead.org> + - Multituner support and i2c address binding + This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or @@ -45,10 +48,18 @@ static int i2c_debug; static int i2c_hw; static int i2c_scan; module_param(i2c_debug, int, 0644); +MODULE_PARM_DESC(i2c_hw,"configure i2c debug level"); module_param(i2c_hw, int, 0444); +MODULE_PARM_DESC(i2c_hw,"force use of hardware i2c support, " + "instead of software bitbang"); module_param(i2c_scan, int, 0444); MODULE_PARM_DESC(i2c_scan,"scan i2c bus at insmod time"); +static unsigned int i2c_udelay = 5; +module_param(i2c_udelay, int, 0444); +MODULE_PARM_DESC(i2c_udelay,"soft i2c delay at insmod time, in usecs " + "(should be 5 or higher). Lower value means higher bus speed."); + /* ----------------------------------------------------------------------- */ /* I2C functions - bitbanging adapter (software i2c) */ @@ -426,6 +437,11 @@ int __devinit init_bttv_i2c(struct bttv *btv) sizeof(bttv_i2c_adap_hw_template)); } else { /* bt848 */ + /* Prevents usage of invalid delay values */ + if (i2c_udelay<5) + i2c_udelay=5; + bttv_i2c_algo_bit_template.udelay=i2c_udelay; + memcpy(&btv->c.i2c_adap, &bttv_i2c_adap_sw_template, sizeof(bttv_i2c_adap_sw_template)); memcpy(&btv->i2c_algo, &bttv_i2c_algo_bit_template, |