Jean, Thank you for your response. I am using an AMD CS5535 chip, which is a "companion" chip to the AMD Geode GX processor. It is register-identical to the scx200, so I just copied that driver and modified it work with the CS5535. The detection is totally different - the scx200 is a PCI device, while the CS5535 uses MSRs. I'll probably send out a patch for that (cs5535 driver) in a few days, once I have a chance to clean it up. I swapped the poll & wait and reduced the POLL_TIMEOUT as you suggested. With no other changes, the load time went down to 4.6 seconds. I've timed the poll loop - typically it takes about 100us to send a byte, so I changed the msleep(10) to wait_event_interruptible_timeout() with a timeout of 1. The hope there is that if I can figure out how to enable interrupts, the ISR can just wake_up() the sleeping thread. But I haven't had any luck so far. Anyway, I added all the ignore and force parameters, ie: modprobe lm83 force=0,0x4c ignore=0,0x18,0,0x19,0,0x1a,0,0x29,0,0x2a,0,0x2b,0,0x4d,0,0x4e And the total module load time (of everything) is down to 3.4 seconds. =) I'm happy with that. Detailed modprobe times for i2c modules: lm83=0.38s ds2482=0.57s max6875=0.55s pca9539=0.62s Is that closer to what is expected? Oh, I'm using the lm83 driver with a lm82 chip - and it works great. Thanks, Ben -----Original Message----- From: Jean Delvare [mailto:khali at linux-fr.org] Sent: Thursday, June 09, 2005 11:51 AM To: Gardner, Ben Cc: lm-sensors at lm-sensors.org Subject: Re: How can I skip i2c detection? Hi Ben, > I have a custom motherboard with four i2c devices on it. > - lm83 @ 0x4c Let me know if you have problems with this one. There aren't many LM83s out there, so it might not have been fully tested. > - max6875 @ 0x50 > - pca9539 @ 0x74 > - ds2484 @ 0x18 > > Right now it takes 15.5 seconds to load those four modules. > I see the "i2c-adapter i2c-0: timeout is state write" kernel message > ten times. > When I build those modules with only the correct addresses, the load > time is 5.5 seconds. scx200_acb bus driver? Even 5.5 seconds is more than I would accept. I suspect that you still have a 4 timeouts on the second i2c adapter (one per address you kept). > So, it takes 10 seconds to probe addresses that don't exist. > > I'd like to speed up the module loading without modifying the source. > > Is there a way to tell an i2c module to load only for a specific > address? > I looked at the i2c_detect() function and did not see a way, but > perhaps I just missed it. You can't remove the default address list altogether. However, there is a way to ignore addresses. Try for example: modprobe lm83 ignore=0,0x18,0,0x19,0,0x1a,0,0x29,0,0x2a,0,0x2b,0,0x4d,0,0x4e Not exactly convenient to type (/etc/modprobe.conf will help), but it should work. And you should do the same with all addresses on bus 1, else you'll have timeout on this one too. The other way would be to lower the timeout in the scx200_acb. It is currently set to 1 second: #define POLL_TIMEOUT (HZ) Changing this to say HZ/10 would be more reasonable. Also, in scx200_acb_poll(), polling is done first, then msleep(10), then retry if needed. I would do some stats on the number of cycles actually required to retrieve a value. If it happens to be one cycle most of the time (which I suspect), performance could probably be improved by lowering the msleep value and possibly swapping the test and the msleep. SMBus drivers which use polling (i2c-i801, i2c-viapro) do msleep(1) first, and poll the value after that. -- Jean Delvare
