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SubjectRe: [Xen-devel] [PATCHv1] x86: rtc_cmos platform device requires legacy irqs
Date
David Vrabel <david.vrabel@citrix.com> writes:

> Adding the rtc platform device when there are no legacy irqs (no
> legacy PIC)

No PIC != No legacy IRQs, Hyper-V Gen2 represents such a platform (and
it has RTC on irq8). I've tested this patch against it and it appears to
work because the device is present in ACPI and we initialize it in
drivers/acpi/acpi_cmos_rtc.c, add_rtc_cmos() bails out in the very
beginning as we see PNP0b00 device.

> causes a conflict with other devices that end up using the
> same irq number.
>
> In a single VCPU Xen PV guest we should have:
>
> /proc/interrupts:
> CPU0
> 0: 4934 xen-percpu-virq timer0
> 1: 0 xen-percpu-ipi spinlock0
> 2: 0 xen-percpu-ipi resched0
> 3: 0 xen-percpu-ipi callfunc0
> 4: 0 xen-percpu-virq debug0
> 5: 0 xen-percpu-ipi callfuncsingle0
> 6: 0 xen-percpu-ipi irqwork0
> 7: 321 xen-dyn-event xenbus
> 8: 90 xen-dyn-event hvc_console
> ...
>
> But hvc_console cannot get its interrupt because it is already in use
> by rtc0 and the console does not work.
>
> genirq: Flags mismatch irq 8. 00000000 (hvc_console) vs. 00000000 (rtc0)
>
> The rtc_cmos device requires a particular legacy irq so don't add it
> if there are no legacy irqs.
>
> Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Tested-by: Sander Eikelenboom <linux@eikelenboom.it>
> ---
> arch/x86/kernel/rtc.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
> index cd96852..07c70f1 100644
> --- a/arch/x86/kernel/rtc.c
> +++ b/arch/x86/kernel/rtc.c
> @@ -14,6 +14,7 @@
> #include <asm/time.h>
> #include <asm/intel-mid.h>
> #include <asm/rtc.h>
> +#include <asm/i8259.h>
>
> #ifdef CONFIG_X86_32
> /*
> @@ -200,6 +201,10 @@ static __init int add_rtc_cmos(void)
> }
> #endif
>
> + /* RTC uses legacy IRQs. */
> + if (!nr_legacy_irqs())
> + return -ENODEV;
> +
> platform_device_register(&rtc_device);
> dev_info(&rtc_device.dev,
> "registered platform RTC device (no PNP device found)\n");

--
Vitaly


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