On Fri, Dec 02, 2016 at 10:36:59PM -0800, Todd Brandt wrote: > The USB resume code in the kernel currently uses a set of hard coded > delay values that are defined in the USB 2.0 spec. Specifically these > three have the most effect on resume time: > > - tdrsmdn: resume signal time (20ms - infinity) usb 2.0 spec 7.1.7.7 > - trsmrcy: resume recovery time (10ms) usb 2.0 spec 7.1.7.7 > - trstrcy: reset recovery time (0ms - infinity) usb 2.0 spec 7.1.7.5 > > These values have been padded considerably in order to accomodate > non-compliant devices. > > - tdrsmdn: resume signal time = 40ms > - trsmrcy: resume recovery time = 10ms > - trstrcy: reset recovery time = 50ms > > I propose that we remove the padding and use the spec minumums instead. > > The following patches do this by creating a struct which contains > these three values, and allowing a module parameter to select between > the current defaults and the spec minimums. The patch could be > simplified to just use 3 defines, but I'm wary of making changes to > core USB code without providing a backup and alot of community testing. I think these values have grown over the years due to bad devices being reported. Look at the kernel logs for details. So we can not reduce them by default. That being said, this is a nice change, but I really hate module parameters. > The first part is the core functionality. The second part provides a > debug interface through sysfs to tweak the values directly at runtime. > > I've created a blog entry on 01.org with some analyze_suspend test > cases illustrating the benefits: > > - https://01.org/suspendresume/blogs/tebrandt/2016/usb-resume-optimization-using-spec-minimum-delays Put this link in your first patch changelog please? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
