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Message-Id: <65b9e5f265b02af3b316e59e55450385@gmail.com>
Date: Thu, 7 Nov 2013 20:59:40 +1300
From: Michael Schmitz <schmitzmic@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-m68k@...r.kernel.org, linux-kernel@...r.kernel.org,
Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH 09/17] [m68k] IRQ: add handle_polled_irq() for timer based soft interrupts
Thomas,
>>>> This is a temporary hack to allow timer based polling of the
>>>> Atari ROM port network and USB cards only. Suggestions on how to
>>>> properly handle this in the normal interrupt framework are most
>>>> welcome.
>
> So you're polling devices which have no hardware interrupt from the
> timer interrupt. Of course if there is no interrupt pending on one of
> these devices, this will trigger the spurious detector. By setting the
> POLL_INPROGRESS flag, you're preventing that.
That's the general idea, yes. I am aware I abuse the flag somewhat.
This was
the least invasive fix I came up with (i.e. no risk to cause
regressions elsewhere).
Adding a new IRQ flag would have been my preference, but that seemed a
bit
bold at the time.
> Reading the demultiplex handler it seems you have no way to figure out
> which of the sub interrupts actually triggered the mfptimer_handler,
> right?
Correct.
> I'm not too happy about the POLL flag "abuse". I'd rather have such
Precisely why I asked for this to be reviewed, thanks,
> interrupts explicitely marked as polled by some other interrupt. That
> also excludes such interrupts from the spurious mechanism completely.
>
> Does the following patch solve the problem? You need to call
>
> irq_set_status_flags(irq, IRQ_IS_POLLED);
>
> when setting up the interrupt controller for those polled interrupt
> lines.
This should do the trick, from what I can see. I have tried to test it,
but recent changes
to the m68k vmlinux.lds have thrown a monkey wrench in the works, it
seems (kernels
just won't boot at all). I'll sort that out with Geert and report back.
Much obliged,
Michael
>
> Thanks,
>
> tglx
> -----------------
> diff --git a/include/linux/irq.h b/include/linux/irq.h
> index 56bb0dc..7dc1003 100644
> --- a/include/linux/irq.h
> +++ b/include/linux/irq.h
> @@ -70,6 +70,9 @@ typedef void (*irq_preflow_handler_t)(struct
> irq_data *data);
> * IRQ_MOVE_PCNTXT - Interrupt can be migrated from process context
> * IRQ_NESTED_TRHEAD - Interrupt nests into another thread
> * IRQ_PER_CPU_DEVID - Dev_id is a per-cpu variable
> + * IRQ_IS_POLLED - Always polled by another interrupt. Exclude
> + * it from the spurious interrupt detection
> + * mechanism and from core side polling.
> */
> enum {
> IRQ_TYPE_NONE = 0x00000000,
> @@ -94,12 +97,14 @@ enum {
> IRQ_NESTED_THREAD = (1 << 15),
> IRQ_NOTHREAD = (1 << 16),
> IRQ_PER_CPU_DEVID = (1 << 17),
> + IRQ_IS_POLLED = (1 << 18),
> };
>
> #define IRQF_MODIFY_MASK \
> (IRQ_TYPE_SENSE_MASK | IRQ_NOPROBE | IRQ_NOREQUEST | \
> IRQ_NOAUTOEN | IRQ_MOVE_PCNTXT | IRQ_LEVEL | IRQ_NO_BALANCING | \
> - IRQ_PER_CPU | IRQ_NESTED_THREAD | IRQ_NOTHREAD | IRQ_PER_CPU_DEVID)
> + IRQ_PER_CPU | IRQ_NESTED_THREAD | IRQ_NOTHREAD | IRQ_PER_CPU_DEVID
> | \
> + IRQ_IS_POLLED)
>
> #define IRQ_NO_BALANCING_MASK (IRQ_PER_CPU | IRQ_NO_BALANCING)
>
> diff --git a/kernel/irq/settings.h b/kernel/irq/settings.h
> index 1162f10..3320b84 100644
> --- a/kernel/irq/settings.h
> +++ b/kernel/irq/settings.h
> @@ -14,6 +14,7 @@ enum {
> _IRQ_NO_BALANCING = IRQ_NO_BALANCING,
> _IRQ_NESTED_THREAD = IRQ_NESTED_THREAD,
> _IRQ_PER_CPU_DEVID = IRQ_PER_CPU_DEVID,
> + _IRQ_IS_POLLED = IRQ_IS_POLLED,
> _IRQF_MODIFY_MASK = IRQF_MODIFY_MASK,
> };
>
> @@ -26,6 +27,7 @@ enum {
> #define IRQ_NOAUTOEN GOT_YOU_MORON
> #define IRQ_NESTED_THREAD GOT_YOU_MORON
> #define IRQ_PER_CPU_DEVID GOT_YOU_MORON
> +#define IRQ_IS_POLLED GOT_YOU_MORON
> #undef IRQF_MODIFY_MASK
> #define IRQF_MODIFY_MASK GOT_YOU_MORON
>
> @@ -147,3 +149,8 @@ static inline bool
> irq_settings_is_nested_thread(struct irq_desc *desc)
> {
> return desc->status_use_accessors & _IRQ_NESTED_THREAD;
> }
> +
> +static inline bool irq_settings_is_polled(struct irq_desc *desc)
> +{
> + return desc->status_use_accessors & _IRQ_IS_POLLED;
> +}
> diff --git a/kernel/irq/spurious.c b/kernel/irq/spurious.c
> index 7b5f012..a1d8cc6 100644
> --- a/kernel/irq/spurious.c
> +++ b/kernel/irq/spurious.c
> @@ -67,8 +67,13 @@ static int try_one_irq(int irq, struct irq_desc
> *desc, bool force)
>
> raw_spin_lock(&desc->lock);
>
> - /* PER_CPU and nested thread interrupts are never polled */
> - if (irq_settings_is_per_cpu(desc) ||
> irq_settings_is_nested_thread(desc))
> + /*
> + * PER_CPU, nested thread interrupts and interrupts explicitely
> + * marked polled are excluded from polling.
> + */
> + if (irq_settings_is_per_cpu(desc) ||
> + irq_settings_is_nested_thread(desc) ||
> + irq_settings_is_polled(desc))
> goto out;
>
> /*
> @@ -268,7 +273,8 @@ try_misrouted_irq(unsigned int irq, struct
> irq_desc *desc,
> void note_interrupt(unsigned int irq, struct irq_desc *desc,
> irqreturn_t action_ret)
> {
> - if (desc->istate & IRQS_POLL_INPROGRESS)
> + if (desc->istate & IRQS_POLL_INPROGRESS ||
> + irq_settings_is_polled(desc))
> return;
>
> /* we get here again via the threaded handler */
>
>
>
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