I'm trying to tune a tickless 2.6.31 kernel for an ARM box
(arch/arm/mach-iop32x/n2100.c). Looking at /proc/timer_stats
I see that
usb_hcd_poll_rh_status (rh_timer_func)
is now the #1 cause of timeouts, which prevents the tickless
kernel from extending the periods between timer interrupts.
The machine has VIA EHCI and UHCI controllers. The polling timer
appears if UHCI_HCD is enabled; enabling only EHCI_HCD does not
case the timer to appear.
Is a polling timer really necessary? If it is, why? UHCI bug or
kernel limitation/shortcut?
For reference, here's lspci -n for the UHCI controller in question:
00:04.1 0c03: 1106:3038 (rev 61) (prog-if 00 [UHCI])
Subsystem: 1106:3038
Flags: bus master, medium devsel, latency 22, IRQ 27
I/O ports at 90000820 [size=32]
Capabilities: [80] Power Management version 2
Kernel driver in use: uhci_hcd
/Mikael
--
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
