Re: [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
Hi Will, On 29/03/2021 21.04, Will Deacon wrote: One CPU still needs to be able to mutate the flags of another CPU to fire an IPI; AIUI the per-cpu ops are *not* atomic for concurrent access by multiple CPUs, and in fact there is no API for that, only for "this CPU". Huh, I really thought we had an API for that, but you're right. Oh well! But I'd still suggest a per-cpu atomic_t in that case, rather than the array. Yeah, after digging into the per-cpu stuff earlier and understanding how it works, I agree that a per-cpu atomic makes sense here. Switched it to that (which simplified out a bunch of smp_processor_id() calls too). Thanks! I think a more idiomatic (and portable) way to do this would be to use the relaxed accessors, but with smp_mb__after_atomic() between them. Do you have a good reason for _not_ doing it like that? Not particularly, other than symmetry with the case below. I think it would be better not to rely on arm64-specific ordering unless there's a good reason to. Sounds reasonable, I'll switch to the barrier version. We do need the return data here, and the release semantics (or another barrier before it). But the read below can be made relaxed and a barrier used instead, and then the same patern above except with a plain atomic_or(). Yes, I think using atomic_fetch_or() followed by atomic_read() would be best (obviously with the relevant comments!) atomic_fetch_or_release is sufficient here (atomic_fetch_or is stronger; atomic_fetch_or_relaxed would not be strong enough as this needs to be ordered after any writes prior to sending the IPI; in this case release semantics also make logical sense). It is ordered, right? As the comment says, it "needs to be ordered after the aic_ic_write() above". atomic_fetch_andnot() is *supposed* to be fully ordered and that should include against the writel_relaxed() on AIC_IPI_FLAG. On ARM it turns out it's not quite fully ordered, but the acquire semantics of the read half are sufficient for this case, as they guarantee the flags are always read after the FIQ has been ACKed. Sorry, I missed that the answer to my question was already written in the comment. However, I'm still a bit unsure about whether the memory barriers give you what you need here. The barrier in atomic_fetch_andnot() will order the previous aic_ic_write(AIC_IPI_ACK) for the purposes of other CPUs reading those locations, but it doesn't say anything about when the interrupt controller actually changes state after the Ack. Given that the AIC is mapped Device-nGnRnE, the Arm ARM offers: | Additionally, for Device-nGnRnE memory, a read or write of a Location | in a Memory-mapped peripheral that exhibits side-effects is complete | only when the read or write both: | | * Can begin to affect the state of the Memory-mapped peripheral. | * Can trigger all associated side-effects, whether they affect other | peripheral devices, PEs, or memory. so without AIC documentation I can't tell whether completion of the Ack write just begins the process of an Ack (in which case we might need something like a read-back), or whether the write response back from the AIC only occurs once the Ack has taken effect. Any ideas? Ahh, you're talking about latency within AIC itself... I obviously don't have an authoritative answer to this, though the hardware designer in me wants to say this really ought to be single-cycle type stuff that isn't internally pipelined in a way that would create races. I tried to set up an SMP test case for the atomic-to-AIC sequence in m1n1, but unfortunately I couldn't hit the race window in deliberately racy code (i.e. ack after clearing flags) without widening it even further with at least one dummy load in between, and of course I didn't experience any races with the proper code either. What I can say is that a simple set IPI; ack IPI (in adjacent str instructions) sequence always yields a cleared IPI, and the converse always yields a set IPI. So if there is latency to the operations it seems it would at least be the same for sets and acks and would imply readbacks block, which should still yield equivalently correct results. But of course this is a single-CPU test, so it is not fully representative of what could happen in an SMP scenario. At this point all I can say is I'm inclined to shrug and say we have no evidence of this being something that can happen, and it shouldn't in sane hardware, and hope for the best :-) Thanks, -- Hector Martin (mar...@marcan.st) Public Key: https://mrcn.st/pub
Re: [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
Hi Hector,
On Fri, Mar 26, 2021 at 05:58:15PM +0900, Hector Martin wrote:
> On 25/03/2021 04.57, Will Deacon wrote:
> > > + event = readl(ic->base + AIC_EVENT);
> > > + type = FIELD_GET(AIC_EVENT_TYPE, event);
> > > + irq = FIELD_GET(AIC_EVENT_NUM, event);
> > > +
> > > + if (type == AIC_EVENT_TYPE_HW)
> > > + handle_domain_irq(aic_irqc->hw_domain, irq, regs);
> > > + else if (type == AIC_EVENT_TYPE_IPI && irq == 1)
> > > + aic_handle_ipi(regs);
> > > + else if (event != 0)
> > > + pr_err("Unknown IRQ event %d, %d\n", type, irq);
> > > + } while (event);
> > > +
> > > + /*
> > > + * vGIC maintenance interrupts end up here too, so we need to check
> > > + * for them separately. Just report and disable vGIC for now, until
> > > + * we implement this properly.
> > > + */
> > > + if ((read_sysreg_s(SYS_ICH_HCR_EL2) & ICH_HCR_EN) &&
> > > + read_sysreg_s(SYS_ICH_MISR_EL2) != 0) {
> > > + pr_err("vGIC IRQ fired, disabling.\n");
> > > + sysreg_clear_set_s(SYS_ICH_HCR_EL2, ICH_HCR_EN, 0);
> > > + }
> >
> > What prevents all these system register accesses being speculated up before
> > the handler?
>
> Nothing, but that's not a problem, is it? If the condition is met, it means
> the vGIC IRQ *is* firing and needs clearing. We don't particularly care if
> this happens before, after, or during the rest of the IRQ handling.
>
> I changed the message to this, because we actually should never hit this
> path with correctly-working KVM code (it takes care of it before this
> handler runs):
>
> pr_err_ratelimited("vGIC IRQ fired and not handled by KVM, disabling.\n");
Looks good.
> > > +static struct irq_chip aic_chip = {
> > > + .name = "AIC",
> > > + .irq_mask = aic_irq_mask,
> > > + .irq_unmask = aic_irq_unmask,
> >
> > I know these are driven by the higher-level irq chip code, but I'm a bit
> > confused as to what provides ordering if, e.g. something ends up calling:
> >
> > aic_chip.irq_mask(d);
> > ...
> > aic_chip.irq_unmask(d);
> >
> > I can't see any ISBs in here and they're writing to two different registers,
> > so can we end up with the IRQ masked after this sequence?
>
> Wait, aren't MMIO writes to the same peripheral using device-nGnRnE memory
> modes always ordered with respect to each other? I thought the _relaxed
> versions were only trouble when mixed with memory/DMA buffers, and MMIO for
> any given peripheral always takes effect in program order.
Sorry, this was my mistake -- I seem to have mixed up the MMIO parts with
the system register parts. In this case, aic_irq_[un]mask() are MMIO writes,
so things work out. It's the FIQ mask/unmask code that needs the ISBs.
> > > +static void aic_ipi_mask(struct irq_data *d)
> > > +{
> > > + u32 irq_bit = BIT(irqd_to_hwirq(d));
> > > + int this_cpu = smp_processor_id();
> > > +
> > > + /* No specific ordering requirements needed here. */
> > > + atomic_andnot(irq_bit, _vipi_enable[this_cpu]);
> > > +}
> >
> > Why not use a per-cpu variable here instead of an array of atomics? The pcpu
> > API has things for atomic updates (e.g. or, and, xchg).
>
> One CPU still needs to be able to mutate the flags of another CPU to fire an
> IPI; AIUI the per-cpu ops are *not* atomic for concurrent access by multiple
> CPUs, and in fact there is no API for that, only for "this CPU".
Huh, I really thought we had an API for that, but you're right. Oh well! But
I'd still suggest a per-cpu atomic_t in that case, rather than the array.
> > > +static void aic_ipi_unmask(struct irq_data *d)
> > > +{
> > > + struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
> > > + u32 irq_bit = BIT(irqd_to_hwirq(d));
> > > + int this_cpu = smp_processor_id();
> > > +
> > > + /*
> > > + * This must complete before the atomic_read_acquire() below to avoid
> > > + * racing aic_ipi_send_mask(). Use a dummy fetch op with release
> > > + * semantics for this. This is arch-specific: ARMv8 B2.3.3 specifies
> > > + * that writes with Release semantics are Barrier-ordered-before reads
> > > + * with Acquire semantics, even though the Linux arch-independent
> > > + * definition of these atomic ops does not.
> > > + */
> >
> > I think a more idiomatic (and portable) way to do this would be to use
> > the relaxed accessors, but with smp_mb__after_atomic() between them. Do you
> > have a good reason for _not_ doing it like that?
>
> Not particularly, other than symmetry with the case below.
I think it would be better not to rely on arm64-specific ordering unless
there's a good reason to.
> > > + /*
> > > + * This sequence is the mirror of the one in aic_ipi_unmask();
> > > + * see the comment there. Additionally, release semantics
> > > + * ensure that the vIPI flag set is ordered after any shared
> > > + * memory accesses that precede it. This therefore also pairs
> > > + * with the
Re: [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
On 06/03/2021 00.05, Andy Shevchenko wrote:
+#define pr_fmt(fmt) "%s: " fmt, __func__
This is not needed, really, if you have unique / distinguishable
messages in the first place.
Rather people include module names, which may be useful.
Makes sense, I'll switch to KBUILD_MODNAME.
+#define MASK_BIT(x)BIT((x) & 0x1f)
GENMASK(4,0)
It's not really a register bitmask, but rather extracting the low bits
of an index... but sure, GENMASK also expresses that. Changed.
+static atomic_t aic_vipi_flag[AIC_MAX_CPUS];
+static atomic_t aic_vipi_enable[AIC_MAX_CPUS];
Isn't it easier to handle these when they are full width, i.e. 32
items per the array?
I don't think so, it doesn't really buy us anything. It's just a maximum
beyond which the driver doesn't work in its current state anyway (if the
number were much larger it'd make sense to dynamically allocate these,
but not at this point).
+static int aic_irq_set_affinity(struct irq_data *d,
+ const struct cpumask *mask_val, bool force)
+{
+ irq_hw_number_t hwirq = irqd_to_hwirq(d);
+ struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
+ int cpu;
+
+ if (hwirq > ic->nr_hw)
>= ?
Good catch, but this is actually obsolete. Higher IRQs go into the FIQ
irqchip, so this should never happen (it's a leftover from when they
were a single one). I'll remove it.
Ack on the other comments, thanks!
--
Hector Martin (mar...@marcan.st)
Public Key: https://mrcn.st/pub
Re: [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
Hi Will,
No worries, I was busy until a couple days ago anyway.
On 25/03/2021 04.57, Will Deacon wrote:
+#define pr_fmt(fmt) "%s: " fmt, __func__
General nit: but I suspect many of the prints in here probably want to be
using the *_ratelimited variants.
You're right, everything complaining about spurious/unsupported stuff is
probably safer rate-limited. I also made them all pr_err_ratelimited,
since nothing should be trying to use that hardware before we get around
to supporting it in this driver.
+static void __exception_irq_entry aic_handle_irq(struct pt_regs *regs)
+{
+ struct aic_irq_chip *ic = aic_irqc;
+ u32 event, type, irq;
+
+ do {
+ /*
+* We cannot use a relaxed read here, as DMA needs to be
+* ordered with respect to the IRQ firing.
+*/
I think this could be a bit clearer: the readl() doesn't order any DMA
accesses, but instead means that subsequent reads by the CPU are ordered
(which may be from a buffer which was DMA'd to) are ordered after the
read of the MMIO register.
Good point, reworded it for v4:
/*
* We cannot use a relaxed read here, as reads from DMA buffers
* need to be ordered after the IRQ fires.
*/
+ event = readl(ic->base + AIC_EVENT);
+ type = FIELD_GET(AIC_EVENT_TYPE, event);
+ irq = FIELD_GET(AIC_EVENT_NUM, event);
+
+ if (type == AIC_EVENT_TYPE_HW)
+ handle_domain_irq(aic_irqc->hw_domain, irq, regs);
+ else if (type == AIC_EVENT_TYPE_IPI && irq == 1)
+ aic_handle_ipi(regs);
+ else if (event != 0)
+ pr_err("Unknown IRQ event %d, %d\n", type, irq);
+ } while (event);
+
+ /*
+* vGIC maintenance interrupts end up here too, so we need to check
+* for them separately. Just report and disable vGIC for now, until
+* we implement this properly.
+*/
+ if ((read_sysreg_s(SYS_ICH_HCR_EL2) & ICH_HCR_EN) &&
+ read_sysreg_s(SYS_ICH_MISR_EL2) != 0) {
+ pr_err("vGIC IRQ fired, disabling.\n");
+ sysreg_clear_set_s(SYS_ICH_HCR_EL2, ICH_HCR_EN, 0);
+ }
What prevents all these system register accesses being speculated up before
the handler?
Nothing, but that's not a problem, is it? If the condition is met, it
means the vGIC IRQ *is* firing and needs clearing. We don't particularly
care if this happens before, after, or during the rest of the IRQ handling.
I changed the message to this, because we actually should never hit this
path with correctly-working KVM code (it takes care of it before this
handler runs):
pr_err_ratelimited("vGIC IRQ fired and not handled by KVM, disabling.\n");
+static struct irq_chip aic_chip = {
+ .name = "AIC",
+ .irq_mask = aic_irq_mask,
+ .irq_unmask = aic_irq_unmask,
I know these are driven by the higher-level irq chip code, but I'm a bit
confused as to what provides ordering if, e.g. something ends up calling:
aic_chip.irq_mask(d);
...
aic_chip.irq_unmask(d);
I can't see any ISBs in here and they're writing to two different registers,
so can we end up with the IRQ masked after this sequence?
Wait, aren't MMIO writes to the same peripheral using device-nGnRnE
memory modes always ordered with respect to each other? I thought the
_relaxed versions were only trouble when mixed with memory/DMA buffers,
and MMIO for any given peripheral always takes effect in program order.
+static void aic_ipi_mask(struct irq_data *d)
+{
+ u32 irq_bit = BIT(irqd_to_hwirq(d));
+ int this_cpu = smp_processor_id();
+
+ /* No specific ordering requirements needed here. */
+ atomic_andnot(irq_bit, _vipi_enable[this_cpu]);
+}
Why not use a per-cpu variable here instead of an array of atomics? The pcpu
API has things for atomic updates (e.g. or, and, xchg).
One CPU still needs to be able to mutate the flags of another CPU to
fire an IPI; AIUI the per-cpu ops are *not* atomic for concurrent access
by multiple CPUs, and in fact there is no API for that, only for "this CPU".
+static void aic_ipi_unmask(struct irq_data *d)
+{
+ struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
+ u32 irq_bit = BIT(irqd_to_hwirq(d));
+ int this_cpu = smp_processor_id();
+
+ /*
+* This must complete before the atomic_read_acquire() below to avoid
+* racing aic_ipi_send_mask(). Use a dummy fetch op with release
+* semantics for this. This is arch-specific: ARMv8 B2.3.3 specifies
+* that writes with Release semantics are Barrier-ordered-before reads
+* with Acquire semantics, even though the Linux arch-independent
+* definition of these atomic ops does not.
+*/
I think a more idiomatic (and portable) way to do this would be to use
the relaxed accessors, but with smp_mb__after_atomic()
Re: [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
On 08/03/2021 22.31, Marc Zyngier wrote:
+ if ((read_sysreg_s(SYS_ICH_HCR_EL2) & ICH_HCR_EN) &&
+ read_sysreg_s(SYS_ICH_MISR_EL2) != 0) {
+ pr_err("vGIC IRQ fired, disabling.\n");
Please add a _ratelimited here. Whilst debugging KVM on this machine,
I ended up with this firing at such a rate that it was impossible to
do anything useful. Ratelimiting it allowed me to pinpoint the
problem.
Ouch. Done for v4.
+static void aic_fiq_eoi(struct irq_data *d)
+{
+ /* We mask to ack (where we can), so we need to unmask at EOI. */
+ if (!irqd_irq_disabled(d) && !irqd_irq_masked(d))
Ah, be careful here: irqd_irq_masked() doesn't do what you think it
does for per-CPU interrupts. It's been on my list to fix for the rVIC
implementation, but I never got around to doing it, and all decent ICs
hide this from SW by having a HW-managed mask, similar to what is on
the IRQ side.
I can see two possibilities:
- you can track the masked state directly and use that instead of
these predicates
- you can just drop the masking altogether as this is only useful to a
hosted hypervisor (KVM), which will have to do its own masking
behind the scenes anyway
Since you're using the masking in KVM after all, I'm tracking the mask
state in a percpu variable now. Also folded in your two minor bugfixes
from the KVM series. Cheers!
--
Hector Martin (mar...@marcan.st)
Public Key: https://mrcn.st/pub
Re: [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
Hi Hector,
Sorry it took me so long to get to this. Some comments below.
On Fri, Mar 05, 2021 at 06:38:51AM +0900, Hector Martin wrote:
> This is the root interrupt controller used on Apple ARM SoCs such as the
> M1. This irqchip driver performs multiple functions:
>
> * Handles both IRQs and FIQs
>
> * Drives the AIC peripheral itself (which handles IRQs)
>
> * Dispatches FIQs to downstream hard-wired clients (currently the ARM
> timer).
>
> * Implements a virtual IPI multiplexer to funnel multiple Linux IPIs
> into a single hardware IPI
>
> Signed-off-by: Hector Martin
> ---
> MAINTAINERS | 2 +
> drivers/irqchip/Kconfig | 8 +
> drivers/irqchip/Makefile| 1 +
> drivers/irqchip/irq-apple-aic.c | 710
> include/linux/cpuhotplug.h | 1 +
> 5 files changed, 722 insertions(+)
> create mode 100644 drivers/irqchip/irq-apple-aic.c
[...]
> + * Implementation notes:
> + *
> + * - This driver creates two IRQ domains, one for HW IRQs and internal FIQs,
> + * and one for IPIs.
> + * - Since Linux needs more than 2 IPIs, we implement a software IRQ
> controller
> + * and funnel all IPIs into one per-CPU IPI (the second "self" IPI is
> unused).
> + * - FIQ hwirq numbers are assigned after true hwirqs, and are per-cpu.
> + * - DT bindings use 3-cell form (like GIC):
> + * - <0 nr flags> - hwirq #nr
> + * - <1 nr flags> - FIQ #nr
> + * - nr=0 Physical HV timer
> + * - nr=1 Virtual HV timer
> + * - nr=2 Physical guest timer
> + * - nr=3 Virtual guest timer
> + *
> + */
> +
> +#define pr_fmt(fmt) "%s: " fmt, __func__
General nit: but I suspect many of the prints in here probably want to be
using the *_ratelimited variants.
> +static void __exception_irq_entry aic_handle_irq(struct pt_regs *regs)
> +{
> + struct aic_irq_chip *ic = aic_irqc;
> + u32 event, type, irq;
> +
> + do {
> + /*
> + * We cannot use a relaxed read here, as DMA needs to be
> + * ordered with respect to the IRQ firing.
> + */
I think this could be a bit clearer: the readl() doesn't order any DMA
accesses, but instead means that subsequent reads by the CPU are ordered
(which may be from a buffer which was DMA'd to) are ordered after the
read of the MMIO register.
> + event = readl(ic->base + AIC_EVENT);
> + type = FIELD_GET(AIC_EVENT_TYPE, event);
> + irq = FIELD_GET(AIC_EVENT_NUM, event);
> +
> + if (type == AIC_EVENT_TYPE_HW)
> + handle_domain_irq(aic_irqc->hw_domain, irq, regs);
> + else if (type == AIC_EVENT_TYPE_IPI && irq == 1)
> + aic_handle_ipi(regs);
> + else if (event != 0)
> + pr_err("Unknown IRQ event %d, %d\n", type, irq);
> + } while (event);
> +
> + /*
> + * vGIC maintenance interrupts end up here too, so we need to check
> + * for them separately. Just report and disable vGIC for now, until
> + * we implement this properly.
> + */
> + if ((read_sysreg_s(SYS_ICH_HCR_EL2) & ICH_HCR_EN) &&
> + read_sysreg_s(SYS_ICH_MISR_EL2) != 0) {
> + pr_err("vGIC IRQ fired, disabling.\n");
> + sysreg_clear_set_s(SYS_ICH_HCR_EL2, ICH_HCR_EN, 0);
> + }
What prevents all these system register accesses being speculated up before
the handler?
> +}
> +
> +static int aic_irq_set_affinity(struct irq_data *d,
> + const struct cpumask *mask_val, bool force)
> +{
> + irq_hw_number_t hwirq = irqd_to_hwirq(d);
> + struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
> + int cpu;
> +
> + if (hwirq > ic->nr_hw)
> + return -EINVAL;
> +
> + if (force)
> + cpu = cpumask_first(mask_val);
> + else
> + cpu = cpumask_any_and(mask_val, cpu_online_mask);
> +
> + aic_ic_write(ic, AIC_TARGET_CPU + hwirq * 4, BIT(cpu));
> + irq_data_update_effective_affinity(d, cpumask_of(cpu));
> +
> + return IRQ_SET_MASK_OK;
> +}
> +
> +static int aic_irq_set_type(struct irq_data *d, unsigned int type)
> +{
> + return (type == IRQ_TYPE_LEVEL_HIGH) ? 0 : -EINVAL;
> +}
> +
> +static struct irq_chip aic_chip = {
> + .name = "AIC",
> + .irq_mask = aic_irq_mask,
> + .irq_unmask = aic_irq_unmask,
I know these are driven by the higher-level irq chip code, but I'm a bit
confused as to what provides ordering if, e.g. something ends up calling:
aic_chip.irq_mask(d);
...
aic_chip.irq_unmask(d);
I can't see any ISBs in here and they're writing to two different registers,
so can we end up with the IRQ masked after this sequence?
> +/*
> + * IPI irqchip
> + */
> +
> +static void aic_ipi_mask(struct irq_data *d)
> +{
> + u32 irq_bit = BIT(irqd_to_hwirq(d));
> + int this_cpu = smp_processor_id();
> +
> + /* No specific ordering requirements needed here. */
> +
Re: [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
On Thu, 04 Mar 2021 21:38:51 +,
Hector Martin wrote:
>
> This is the root interrupt controller used on Apple ARM SoCs such as the
> M1. This irqchip driver performs multiple functions:
>
> * Handles both IRQs and FIQs
>
> * Drives the AIC peripheral itself (which handles IRQs)
>
> * Dispatches FIQs to downstream hard-wired clients (currently the ARM
> timer).
>
> * Implements a virtual IPI multiplexer to funnel multiple Linux IPIs
> into a single hardware IPI
>
[...]
> Signed-off-by: Hector Martin
> +static void __exception_irq_entry aic_handle_irq(struct pt_regs *regs)
> +{
> + struct aic_irq_chip *ic = aic_irqc;
> + u32 event, type, irq;
> +
> + do {
> + /*
> + * We cannot use a relaxed read here, as DMA needs to be
> + * ordered with respect to the IRQ firing.
> + */
> + event = readl(ic->base + AIC_EVENT);
> + type = FIELD_GET(AIC_EVENT_TYPE, event);
> + irq = FIELD_GET(AIC_EVENT_NUM, event);
> +
> + if (type == AIC_EVENT_TYPE_HW)
> + handle_domain_irq(aic_irqc->hw_domain, irq, regs);
> + else if (type == AIC_EVENT_TYPE_IPI && irq == 1)
> + aic_handle_ipi(regs);
> + else if (event != 0)
> + pr_err("Unknown IRQ event %d, %d\n", type, irq);
> + } while (event);
> +
> + /*
> + * vGIC maintenance interrupts end up here too, so we need to check
> + * for them separately. Just report and disable vGIC for now, until
> + * we implement this properly.
> + */
> + if ((read_sysreg_s(SYS_ICH_HCR_EL2) & ICH_HCR_EN) &&
> + read_sysreg_s(SYS_ICH_MISR_EL2) != 0) {
> + pr_err("vGIC IRQ fired, disabling.\n");
Please add a _ratelimited here. Whilst debugging KVM on this machine,
I ended up with this firing at such a rate that it was impossible to
do anything useful. Ratelimiting it allowed me to pinpoint the
problem.
[...]
> +/*
> + * FIQ irqchip
> + */
> +
> +static void aic_fiq_mask(struct irq_data *d)
> +{
> + /* Only the guest timers have real mask bits, unfortunately. */
> + switch (d->hwirq) {
> + case AIC_TMR_GUEST_PHYS:
> + sysreg_clear_set_s(SYS_APL_VM_TMR_FIQ_ENA_EL1,
> VM_TMR_FIQ_ENABLE_P, 0);
> + break;
> + case AIC_TMR_GUEST_VIRT:
> + sysreg_clear_set_s(SYS_APL_VM_TMR_FIQ_ENA_EL1,
> VM_TMR_FIQ_ENABLE_V, 0);
> + break;
> + }
> +}
> +
> +static void aic_fiq_unmask(struct irq_data *d)
> +{
> + switch (d->hwirq) {
> + case AIC_TMR_GUEST_PHYS:
> + sysreg_clear_set_s(SYS_APL_VM_TMR_FIQ_ENA_EL1, 0,
> VM_TMR_FIQ_ENABLE_P);
> + break;
> + case AIC_TMR_GUEST_VIRT:
> + sysreg_clear_set_s(SYS_APL_VM_TMR_FIQ_ENA_EL1, 0,
> VM_TMR_FIQ_ENABLE_V);
> + break;
> + }
> +}
> +
> +static void aic_fiq_eoi(struct irq_data *d)
> +{
> + /* We mask to ack (where we can), so we need to unmask at EOI. */
> + if (!irqd_irq_disabled(d) && !irqd_irq_masked(d))
Ah, be careful here: irqd_irq_masked() doesn't do what you think it
does for per-CPU interrupts. It's been on my list to fix for the rVIC
implementation, but I never got around to doing it, and all decent ICs
hide this from SW by having a HW-managed mask, similar to what is on
the IRQ side.
I can see two possibilities:
- you can track the masked state directly and use that instead of
these predicates
- you can just drop the masking altogether as this is only useful to a
hosted hypervisor (KVM), which will have to do its own masking
behind the scenes anyway
> + aic_fiq_unmask(d);
> +}
> +
The rest looks good to me.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
Re: [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
On Mon, Mar 8, 2021 at 1:50 PM Marc Zyngier wrote: > On Fri, 05 Mar 2021 15:05:08 +, > Andy Shevchenko wrote: ... > > > +#define TIMER_FIRING(x) > > > \ > > > + (((x) & (ARCH_TIMER_CTRL_ENABLE | ARCH_TIMER_CTRL_IT_MASK | > > > \ > > > +ARCH_TIMER_CTRL_IT_STAT)) == > > > \ > > > +(ARCH_TIMER_CTRL_ENABLE | ARCH_TIMER_CTRL_IT_STAT)) > > > > It's a bit hard to read. Perhaps > > > > #define FOO_MASK (_ENABLE | _STAT) > > #define _FIRING ... (FOO_MASK | _MASK == FOO_MASK) > > The expression above is a direct translation of the architecture > reference manual, and I'd rather not have that hidden behind a bunch > of obscure macros. OK! ... > > > + irqc->hw_domain = > > > irq_domain_create_linear(of_node_to_fwnode(node), > > > + irqc->nr_hw + > > > AIC_NR_FIQ, > > > + _irq_domain_ops, > > > irqc); > > > > If you are sure it will be always OF-only, why not to use > > irq_domain_add_linear()? > > The OF-only API is deprecated, and there is no point in using it for > *new* code, specially when things like IPI allocation require the use > of the modern API. For arm64 root controllers, that's the way to go. Good to know, thanks! -- With Best Regards, Andy Shevchenko
Re: [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
On Fri, 05 Mar 2021 15:05:08 +, Andy Shevchenko wrote: [...] > > +#define TIMER_FIRING(x) > > \ > > + (((x) & (ARCH_TIMER_CTRL_ENABLE | ARCH_TIMER_CTRL_IT_MASK | > >\ > > +ARCH_TIMER_CTRL_IT_STAT)) == > >\ > > +(ARCH_TIMER_CTRL_ENABLE | ARCH_TIMER_CTRL_IT_STAT)) > > It's a bit hard to read. Perhaps > > #define FOO_MASK (_ENABLE | _STAT) > #define _FIRING ... (FOO_MASK | _MASK == FOO_MASK) The expression above is a direct translation of the architecture reference manual, and I'd rather not have that hidden behind a bunch of obscure macros. [...] > > + irqc->hw_domain = irq_domain_create_linear(of_node_to_fwnode(node), > > + irqc->nr_hw + AIC_NR_FIQ, > > + _irq_domain_ops, > > irqc); > > If you are sure it will be always OF-only, why not to use > irq_domain_add_linear()? The OF-only API is deprecated, and there is no point in using it for *new* code, specially when things like IPI allocation require the use of the modern API. For arm64 root controllers, that's the way to go. Thanks, M. -- Without deviation from the norm, progress is not possible.
Re: [RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
On Thu, Mar 4, 2021 at 11:41 PM Hector Martin wrote:
>
> This is the root interrupt controller used on Apple ARM SoCs such as the
> M1. This irqchip driver performs multiple functions:
>
> * Handles both IRQs and FIQs
>
> * Drives the AIC peripheral itself (which handles IRQs)
>
> * Dispatches FIQs to downstream hard-wired clients (currently the ARM
> timer).
>
> * Implements a virtual IPI multiplexer to funnel multiple Linux IPIs
> into a single hardware IPI
...
> + * - <0 nr flags> - hwirq #nr
> + * - <1 nr flags> - FIQ #nr
> + * - nr=0 Physical HV timer
> + * - nr=1 Virtual HV timer
> + * - nr=2 Physical guest timer
> + * - nr=3 Virtual guest timer
> + *
Unneeded blank line.
> + */
...
> +#define pr_fmt(fmt) "%s: " fmt, __func__
This is not needed, really, if you have unique / distinguishable
messages in the first place.
Rather people include module names, which may be useful.
...
> +#define MASK_REG(x)(4 * ((x) >> 5))
> +#define MASK_BIT(x)BIT((x) & 0x1f)
GENMASK(4,0)
...
> +/*
> + * Max 31 bits in IPI SEND register (top bit is self).
> + * >=32-core chips will need code changes anyway.
> + */
> +#define AIC_MAX_CPUS 31
I would put it as (32 - 1) to show that the register is actually 32-bit long.
...
> +static atomic_t aic_vipi_flag[AIC_MAX_CPUS];
> +static atomic_t aic_vipi_enable[AIC_MAX_CPUS];
Isn't it easier to handle these when they are full width, i.e. 32
items per the array?
...
> +static int aic_irq_set_affinity(struct irq_data *d,
> + const struct cpumask *mask_val, bool force)
> +{
> + irq_hw_number_t hwirq = irqd_to_hwirq(d);
> + struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
> + int cpu;
> +
> + if (hwirq > ic->nr_hw)
>= ?
> + return -EINVAL;
> +
> + if (force)
> + cpu = cpumask_first(mask_val);
> + else
> + cpu = cpumask_any_and(mask_val, cpu_online_mask);
> +
> + aic_ic_write(ic, AIC_TARGET_CPU + hwirq * 4, BIT(cpu));
> + irq_data_update_effective_affinity(d, cpumask_of(cpu));
> +
> + return IRQ_SET_MASK_OK;
> +}
...
> +static void aic_fiq_mask(struct irq_data *d)
> +{
> + /* Only the guest timers have real mask bits, unfortunately. */
> + switch (d->hwirq) {
> + case AIC_TMR_GUEST_PHYS:
> + sysreg_clear_set_s(SYS_APL_VM_TMR_FIQ_ENA_EL1,
> VM_TMR_FIQ_ENABLE_P, 0);
> + break;
> + case AIC_TMR_GUEST_VIRT:
> + sysreg_clear_set_s(SYS_APL_VM_TMR_FIQ_ENA_EL1,
> VM_TMR_FIQ_ENABLE_V, 0);
> + break;
default case? // some compilers may not be happy
Ditto for all similar places in the series.
> + }
> +}
...
> +#define TIMER_FIRING(x)
> \
> + (((x) & (ARCH_TIMER_CTRL_ENABLE | ARCH_TIMER_CTRL_IT_MASK |
> \
> +ARCH_TIMER_CTRL_IT_STAT)) ==
> \
> +(ARCH_TIMER_CTRL_ENABLE | ARCH_TIMER_CTRL_IT_STAT))
It's a bit hard to read. Perhaps
#define FOO_MASK (_ENABLE | _STAT)
#define _FIRING ... (FOO_MASK | _MASK == FOO_MASK)
?
...
> + if ((read_sysreg_s(SYS_APL_PMCR0_EL1) & (PMCR0_IMODE | PMCR0_IACT))
> + == (FIELD_PREP(PMCR0_IMODE, PMCR0_IMODE_FIQ) |
> PMCR0_IACT)) {
It's better to have == on the previous line.
...
> + for_each_set_bit(i, , AIC_NR_SWIPI) {
> + handle_domain_irq(aic_irqc->ipi_domain, i, regs);
> + }
No {} needed.
...
> +static int aic_init_smp(struct aic_irq_chip *irqc, struct device_node *node)
> +{
> + int base_ipi;
Introducing a temporary variable may help with readability
... *d = irqc->hw_domain;
> + irqc->ipi_domain = irq_domain_create_linear(irqc->hw_domain->fwnode,
> AIC_NR_SWIPI,
> + _ipi_domain_ops,
> irqc);
> + if (WARN_ON(!irqc->ipi_domain))
> + return -ENODEV;
> +
> + irqc->ipi_domain->flags |= IRQ_DOMAIN_FLAG_IPI_SINGLE;
> + irq_domain_update_bus_token(irqc->ipi_domain, DOMAIN_BUS_IPI);
> +
> + base_ipi = __irq_domain_alloc_irqs(irqc->ipi_domain, -1, AIC_NR_SWIPI,
> + NUMA_NO_NODE, NULL, false, NULL);
> +
> + if (WARN_ON(!base_ipi)) {
> + irq_domain_remove(irqc->ipi_domain);
> + return -ENODEV;
> + }
> +
> + set_smp_ipi_range(base_ipi, AIC_NR_SWIPI);
> +
> + return 0;
> +}
...
> + return 0;
> +
Extra blank line.
...
> + irqc->hw_domain = irq_domain_create_linear(of_node_to_fwnode(node),
> + irqc->nr_hw + AIC_NR_FIQ,
> + _irq_domain_ops, irqc);
If you are sure it will be always OF-only, why not to use
irq_domain_add_linear()?
...
> + for (i = 0; i <
[RFT PATCH v3 16/27] irqchip/apple-aic: Add support for the Apple Interrupt Controller
This is the root interrupt controller used on Apple ARM SoCs such as the M1. This irqchip driver performs multiple functions: * Handles both IRQs and FIQs * Drives the AIC peripheral itself (which handles IRQs) * Dispatches FIQs to downstream hard-wired clients (currently the ARM timer). * Implements a virtual IPI multiplexer to funnel multiple Linux IPIs into a single hardware IPI Signed-off-by: Hector Martin --- MAINTAINERS | 2 + drivers/irqchip/Kconfig | 8 + drivers/irqchip/Makefile| 1 + drivers/irqchip/irq-apple-aic.c | 710 include/linux/cpuhotplug.h | 1 + 5 files changed, 722 insertions(+) create mode 100644 drivers/irqchip/irq-apple-aic.c diff --git a/MAINTAINERS b/MAINTAINERS index 744e086d28cd..28bd46f4f7a7 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -1648,6 +1648,8 @@ T:git https://github.com/AsahiLinux/linux.git F: Documentation/devicetree/bindings/arm/apple.yaml F: Documentation/devicetree/bindings/interrupt-controller/apple,aic.yaml F: arch/arm64/include/asm/sysreg_apple.h +F: drivers/irqchip/irq-apple-aic.c +F: include/dt-bindings/interrupt-controller/apple-aic.h ARM/ARTPEC MACHINE SUPPORT M: Jesper Nilsson diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig index 15536e321df5..d3a14f304ec8 100644 --- a/drivers/irqchip/Kconfig +++ b/drivers/irqchip/Kconfig @@ -577,4 +577,12 @@ config MST_IRQ help Support MStar Interrupt Controller. +config APPLE_AIC + bool "Apple Interrupt Controller (AIC)" + depends on ARM64 + default ARCH_APPLE + help + Support for the Apple Interrupt Controller found on Apple Silicon SoCs, + such as the M1. + endmenu diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile index c59b95a0532c..eb6a515f0f64 100644 --- a/drivers/irqchip/Makefile +++ b/drivers/irqchip/Makefile @@ -113,3 +113,4 @@ obj-$(CONFIG_LOONGSON_PCH_MSI) += irq-loongson-pch-msi.o obj-$(CONFIG_MST_IRQ) += irq-mst-intc.o obj-$(CONFIG_SL28CPLD_INTC)+= irq-sl28cpld.o obj-$(CONFIG_MACH_REALTEK_RTL) += irq-realtek-rtl.o +obj-$(CONFIG_APPLE_AIC)+= irq-apple-aic.o diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c new file mode 100644 index ..ddc0856f36a5 --- /dev/null +++ b/drivers/irqchip/irq-apple-aic.c @@ -0,0 +1,710 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright The Asahi Linux Contributors + * + * Based on irq-lpc32xx: + * Copyright 2015-2016 Vladimir Zapolskiy + * Based on irq-bcm2836: + * Copyright 2015 Broadcom + */ + +/* + * AIC is a fairly simple interrupt controller with the following features: + * + * - 896 level-triggered hardware IRQs + * - Single mask bit per IRQ + * - Per-IRQ affinity setting + * - Automatic masking on event delivery (auto-ack) + * - Software triggering (ORed with hw line) + * - 2 per-CPU IPIs (meant as "self" and "other", but they are + * interchangeable if not symmetric) + * - Automatic prioritization (single event/ack register per CPU, lower IRQs = + * higher priority) + * - Automatic masking on ack + * - Default "this CPU" register view and explicit per-CPU views + * + * In addition, this driver also handles FIQs, as these are routed to the same + * IRQ vector. These are used for Fast IPIs (TODO), the ARMv8 timer IRQs, and + * performance counters (TODO). + * + * Implementation notes: + * + * - This driver creates two IRQ domains, one for HW IRQs and internal FIQs, + * and one for IPIs. + * - Since Linux needs more than 2 IPIs, we implement a software IRQ controller + * and funnel all IPIs into one per-CPU IPI (the second "self" IPI is unused). + * - FIQ hwirq numbers are assigned after true hwirqs, and are per-cpu. + * - DT bindings use 3-cell form (like GIC): + * - <0 nr flags> - hwirq #nr + * - <1 nr flags> - FIQ #nr + * - nr=0 Physical HV timer + * - nr=1 Virtual HV timer + * - nr=2 Physical guest timer + * - nr=3 Virtual guest timer + * + */ + +#define pr_fmt(fmt) "%s: " fmt, __func__ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#define AIC_INFO 0x0004 +#define AIC_INFO_NR_HW GENMASK(15, 0) + +#define AIC_CONFIG 0x0010 + +#define AIC_WHOAMI 0x2000 +#define AIC_EVENT 0x2004 +#define AIC_EVENT_TYPE GENMASK(31, 16) +#define AIC_EVENT_NUM GENMASK(15, 0) + +#define AIC_EVENT_TYPE_HW 1 +#define AIC_EVENT_TYPE_IPI 4 +#define AIC_EVENT_IPI_OTHER1 +#define AIC_EVENT_IPI_SELF 2 + +#define AIC_IPI_SEND 0x2008 +#define AIC_IPI_ACK0x200c +#define AIC_IPI_MASK_SET 0x2024 +#define AIC_IPI_MASK_CLR 0x2028 + +#define AIC_IPI_SEND_CPU(cpu) BIT(cpu) + +#define
