On Sun, 23 May 2010, Grant wrote: > >> Is there any way to set the latency timer for a USB device? > > > > In general, USB devices don't have latency timers. What are you > > referring to? > > > > Alan Stern > > In light of that, I must be looking for a way to set the latency timer > for a USB bus. Some dmesg output: > > ehci_hcd 0000:00:02.1: setting latency timer to 64 > ehci_hcd 0000:00:04.1: setting latency timer to 64 > ohci_hcd 0000:00:02.0: setting latency timer to 64 > ohci_hcd 0000:00:04.0: setting latency timer to 64 > > I'd like to experiment with some different values for fun. ehci-hcd has a module parameter named log2_irq_thresh. Is that what you're interested in? It is the Interrupt Threshold Control value in the EHCI USBCMD register. It doesn't corresponds to those dmesg lines, however -- they come from pcibios_set_master() in arch/x86/pci/i386.c, which is concerned with bus mastering rather than interrupts. And they refer to a PCI control, not a USB control. Alan Stern -- 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
