From 141276b57e1f83a86b8e77554b36511be0a7049c Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Wed, 6 Sep 2006 19:04:28 -0300 Subject: 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 for pointing this improvement. Signed-off-by: Mauro Carvalho Chehab --- drivers/media/video/bt8xx/bttv-i2c.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'drivers/media/video/bt8xx/bttv-i2c.c') diff --git a/drivers/media/video/bt8xx/bttv-i2c.c b/drivers/media/video/bt8xx/bttv-i2c.c index 4b562b386fc..03ee170181f 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 + (c) 2005 Mauro Carvalho Chehab + - 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, -- cgit v1.2.3