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/cx88/cx88-i2c.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'drivers/media/video/cx88/cx88-i2c.c') diff --git a/drivers/media/video/cx88/cx88-i2c.c b/drivers/media/video/cx88/cx88-i2c.c index 2aec4c18268..a74ed632dda 100644 --- a/drivers/media/video/cx88/cx88-i2c.c +++ b/drivers/media/video/cx88/cx88-i2c.c @@ -43,6 +43,11 @@ static unsigned int i2c_scan = 0; 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, 0644); +MODULE_PARM_DESC(i2c_udelay,"i2c delay at insmod time, in usecs " + "(should be 5 or higher). Lower value means higher bus speed."); + #define dprintk(level,fmt, arg...) if (i2c_debug >= level) \ printk(KERN_DEBUG "%s: " fmt, core->name , ## arg) @@ -202,6 +207,11 @@ static void do_i2c_scan(char *name, struct i2c_client *c) /* init + register i2c algo-bit adapter */ int cx88_i2c_init(struct cx88_core *core, struct pci_dev *pci) { + /* Prevents usage of invalid delay values */ + if (i2c_udelay<5) + i2c_udelay=5; + cx8800_i2c_algo_template.udelay=i2c_udelay; + memcpy(&core->i2c_adap, &cx8800_i2c_adap_template, sizeof(core->i2c_adap)); memcpy(&core->i2c_algo, &cx8800_i2c_algo_template, -- cgit v1.2.3