Hi Sebastian, Thomas, Preemp-rt on at91 has multiple issues: 1/ After apply the preempt-rt patch, the kernel doesn't build anymore, arm-at91-pit-remove-irq-handler-when-clock-is-unused.patch is not correct anymore. Can you squash the following patch to solve this build issue? 2/ This approach actually has more issues, in particular, request_irq() must not be calls from interrupt disabled context. That only works because might_sleep() is not active during early boot. For more information, see the following discussion: http://lists.infradead.org/pipermail/linux-arm-kernel/2015-July/357607.html However, we can't remove those patches now because else we would suffer from another issue: The timer interrupt is shared with other devices, in particular the debug tty, the rtc dans the pmc. When using preempt-rt, those interrupts become threaded interrupts. But, the pit interrupt is requested with IRQF_TIMER and so has IRQF_NO_THREAD. If the pit interrupt is not freed at early boot, all the other devices will fail requesting their interrupt, for example: genirq: Flags mismatch irq 16. 00042080 (ttyS0) vs. 00015280 (at91_tick) atmel_usart ffffee00.serial: atmel_startup - Can't get irq I'd say that the proper solution would still be to implement the virtual irqchip because this would still hit people not wanting to use the TCB as their clock source. 3/ Finally, the kernel will crash when initializing the PMC driver. This is solved by this series that will hopefully land in the mainline: http://lists.infradead.org/pipermail/linux-arm-kernel/2015-December/390954.html Alexandre Belloni (1): fix arm-at91-pit-remove-irq-handler-when-clock-is-unused.patch drivers/clocksource/timer-atmel-pit.c | 68 +++++++++++++++++------------------ drivers/clocksource/timer-atmel-st.c | 8 ++--- 2 files changed, 38 insertions(+), 38 deletions(-) -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
