Hi Jean: * Jean Delvare <khali at linux-fr.org> [2007-08-12 14:15:27 +0200]: > Hi Mark, all, > > On Thu, 26 Jul 2007 07:39:58 -0400, Mark M. Hoffman wrote: > > Max rate for standard I2C/SMBus is 100KHz. However, the hardware which is > > most common on PCs usually runs at something like 10KHz. > > Speed which our drivers don't even reach because they don't use > interrupts. > > > > > Ok, I thought it might be along those lines. Is there any other > > > > performance impact to the system while it's waiting for the I2C bus? > > > > > > Good question, I don't know. That's more a question for the I2C > > > mailing list. Jean? > > > > It depends on the specific I2C bus driver. All of the most common ones use > > polling, so unfortunately you will see CPU % go to 100 during that 1.5 sec. > > I don't think so. The I2C bus drivers sleep between polls, so most of > the time is spent sleeping. If we were "actively" polling (without > sleeping) it would be much faster, but would indeed suck the CPU time > so we don't do that. > > Whoever is really concerned about slow I2C bus speed could spend some > time converting his/her I2C bus driver to use interrupts instead of > polling. I wanted to convert the i2c-i801 driver that way but could > never find the time for it. You're right: for some reason I thought they were using mdelay, not msleep. Regards, -- Mark M. Hoffman mhoffman at lightlink.com
