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Message-ID: <cb311ce9-0a37-5933-afd0-4fc6ea4e2570@synopsys.com>
Date: Tue, 8 Nov 2016 12:23:24 -0800
From: Vineet Gupta <Vineet.Gupta1@...opsys.com>
To: Yuriy Kolerov <yuriy.kolerov@...opsys.com>,
"linux-snps-arc@...ts.infradead.org"
<linux-snps-arc@...ts.infradead.org>
CC: "Alexey.Brodkin@...opsys.com" <Alexey.Brodkin@...opsys.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/2] ARC: IRQ: Do not use hwirq as virq and vice versa
On 11/07/2016 11:08 PM, Yuriy Kolerov wrote:
> At first smp_ipi_irq_setup() takes a cpu number and a hwirq number for
> the per core local interrupt line in the root interrupt controller and
> registers an appropriate IPI handler per cpu. However this function tries
> to bind a handler to the hwirq as virtual IRQ number and it is a wrong
> behavior. It is necessary to find a mapping of hwirq in the root IRQ
> domain to the actual virq using irq_find_mapping(). Also a declaration
> of smp_ipi_irq_setup() is corrected to denote that this function takes
> a hardware IRQ number but not a virtual IRQ number.
>
> Also there is one more problem related to usage of IRQ numbers. Multicore
> ARC configurations use IDU (Interrupt Distribution Unit) for distributing
> of common interrupts. In fact IDU is a interrupt controller on top of
> main per core interrupt controller.
>
> All common IRQs are physically and linearly mapped to per core
> interrupts. E.g. <0, 1, 2, 3> common IDU interrupts may be mapped to per
> core <24, 25, 26, 27> interrupts. An initialization code of IDU
> controller (idu_of_init()) creates mappings for all parent interrupts
> <24, 25, ...> and sets a chained IDU handler for them. In the same
> time idu_of_init() must save the first met parent hwirq (idu_first_irq)
> thus in future it is possible to figure out what common hwirq has come
> by subtracting of idu_first_irq from the current parent hwirq (see
> idu_cascade_isr()).
>
> The problem is that idu_of_init() and idu_cascade_isr() use parent virtual
> IRQs as hardware IRQs and perform all the above-described manipulations
> on virtual IRQs. But it is wrong and hardware IRQs must be used instead.
I rephrased the changelog to below
---->
ARC: IRQ: Do not use hwirq as virq and vice versa
This came up when reviewing code to address missing IRQ affinity
setting in AXS103 platform and/or implementing hierarchical IRQ domains
- smp_ipi_irq_setup() callers pass hwirq but in turn calls
request_percpu_irq() which expects a linux virq. So invoke
irq_find_mapping() to do the conversion
(also explicitify this in code by renaming the args appropriately)
- idu_of_init()/idu_cascade_isr() were similarly using linux virq where
hwirq is expected, so do the conversion using irqd_to_hwirq() helper
>
> Signed-off-by: Yuriy Kolerov <yuriy.kolerov@...opsys.com>
> ---
> arch/arc/include/asm/smp.h | 4 ++--
> arch/arc/kernel/mcip.c | 20 +++++++++-----------
> arch/arc/kernel/smp.c | 13 +++++++++----
> 3 files changed, 20 insertions(+), 17 deletions(-)
>
> diff --git a/arch/arc/include/asm/smp.h b/arch/arc/include/asm/smp.h
> index 89fdd1b..0861007 100644
> --- a/arch/arc/include/asm/smp.h
> +++ b/arch/arc/include/asm/smp.h
> @@ -37,9 +37,9 @@ extern const char *arc_platform_smp_cpuinfo(void);
> * API expected BY platform smp code (FROM arch smp code)
> *
> * smp_ipi_irq_setup:
> - * Takes @cpu and @irq to which the arch-common ISR is hooked up
> + * Takes @cpu and @hwirq to which the arch-common ISR is hooked up
> */
> -extern int smp_ipi_irq_setup(int cpu, int irq);
> +extern int smp_ipi_irq_setup(int cpu, irq_hw_number_t hwirq);
>
> /*
> * struct plat_smp_ops - SMP callbacks provided by platform to ARC SMP
> diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c
> index 72f9179..4f4f04b 100644
> --- a/arch/arc/kernel/mcip.c
> +++ b/arch/arc/kernel/mcip.c
> @@ -219,16 +219,14 @@ static struct irq_chip idu_irq_chip = {
>
> };
>
> -static int idu_first_irq;
> +static irq_hw_number_t idu_first_hwirq;
>
> static void idu_cascade_isr(struct irq_desc *desc)
> {
> - struct irq_domain *domain = irq_desc_get_handler_data(desc);
> - unsigned int core_irq = irq_desc_get_irq(desc);
> - unsigned int idu_irq;
> -
> - idu_irq = core_irq - idu_first_irq;
> - generic_handle_irq(irq_find_mapping(domain, idu_irq));
> + struct irq_domain *idu_domain = irq_desc_get_handler_data(desc);
> + irq_hw_number_t core_hwirq = irqd_to_hwirq(irq_desc_get_irq_data(desc));
> + irq_hw_number_t idu_hwirq = core_hwirq - idu_first_hwirq;
> + generic_handle_irq(irq_find_mapping(idu_domain, idu_hwirq));
> }
>
> static int idu_irq_map(struct irq_domain *d, unsigned int virq, irq_hw_number_t hwirq)
> @@ -294,7 +292,7 @@ idu_of_init(struct device_node *intc, struct device_node *parent)
> struct irq_domain *domain;
> /* Read IDU BCR to confirm nr_irqs */
> int nr_irqs = of_irq_count(intc);
> - int i, irq;
> + int i, virq;
>
> if (!idu_detected)
> panic("IDU not detected, but DeviceTree using it");
> @@ -312,11 +310,11 @@ idu_of_init(struct device_node *intc, struct device_node *parent)
> * however we need it to get the parent virq and set IDU handler
> * as first level isr
> */
> - irq = irq_of_parse_and_map(intc, i);
> + virq = irq_of_parse_and_map(intc, i);
> if (!i)
> - idu_first_irq = irq;
> + idu_first_hwirq = irqd_to_hwirq(irq_get_irq_data(virq));
>
> - irq_set_chained_handler_and_data(irq, idu_cascade_isr, domain);
> + irq_set_chained_handler_and_data(virq, idu_cascade_isr, domain);
> }
>
> __mcip_cmd(CMD_IDU_ENABLE, 0);
> diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c
> index f183cc6..692ca51 100644
> --- a/arch/arc/kernel/smp.c
> +++ b/arch/arc/kernel/smp.c
> @@ -22,6 +22,7 @@
> #include <linux/atomic.h>
> #include <linux/cpumask.h>
> #include <linux/reboot.h>
> +#include <linux/irqdomain.h>
> #include <asm/processor.h>
> #include <asm/setup.h>
> #include <asm/mach_desc.h>
> @@ -351,20 +352,24 @@ irqreturn_t do_IPI(int irq, void *dev_id)
> */
> static DEFINE_PER_CPU(int, ipi_dev);
>
> -int smp_ipi_irq_setup(int cpu, int irq)
> +int smp_ipi_irq_setup(int cpu, irq_hw_number_t hwirq)
> {
> int *dev = per_cpu_ptr(&ipi_dev, cpu);
> + unsigned int virq = irq_find_mapping(NULL, hwirq);
> +
> + if (!virq)
> + panic("Cannot find virq for root domain and hwirq=%lu", hwirq);
>
> /* Boot cpu calls request, all call enable */
> if (!cpu) {
> int rc;
>
> - rc = request_percpu_irq(irq, do_IPI, "IPI Interrupt", dev);
> + rc = request_percpu_irq(virq, do_IPI, "IPI Interrupt", dev);
> if (rc)
> - panic("Percpu IRQ request failed for %d\n", irq);
> + panic("Percpu IRQ request failed for %u\n", virq);
> }
>
> - enable_percpu_irq(irq, 0);
> + enable_percpu_irq(virq, 0);
>
> return 0;
> }
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