diff options
| 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/cx88/cx88-i2c.c | |
| parent | 48c06d5e2d63c1d6282c0f7fe67741a39d6c1852 (diff) | |
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/cx88/cx88-i2c.c')
| -rw-r--r-- | drivers/media/video/cx88/cx88-i2c.c | 10 |
1 files changed, 10 insertions, 0 deletions
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, |