Re: [PATCH 09/15] irq: arm: perform irqentry in entry code

Mark Rutland
2021-10-22T17:59:08Z

On Fri, Oct 22, 2021 at 05:34:20PM +0100, Vladimir Murzin wrote:
> On 10/22/21 4:36 PM, Mark Rutland wrote:
> > On Fri, Oct 22, 2021 at 04:18:18PM +0100, Vladimir Murzin wrote:
> >> Hi Mark,
> >>
> >> On 10/21/21 7:02 PM, Mark Rutland wrote:
> >>> +/*
> >>> + * TODO: restructure the ARMv7M entry logic so that this entry logic can live
> >>> + * in arch code.
> >>> + */
> >>> +asmlinkage void __exception_irq_entry
> >>> +static void nvic_handle_irq(irq_hw_number_t hwirq, struct pt_regs *regs)
> >>
> >> I'm seeing build time failure...
> >>
> >> drivers/irqchip/irq-nvic.c:50:8: error: two or more data types in declaration specifiers
> >> static void nvic_handle_irq(irq_hw_number_t hwirq, struct pt_regs *regs)
> >> ^~~~
> >> drivers/irqchip/irq-nvic.c:50:13: warning: 'nvic_handle_irq' defined but not used [-Wunused-function]
> >> static void nvic_handle_irq(irq_hw_number_t hwirq, struct pt_regs *regs)
> >>
> >> I've fixed that locally and planing to give it a go...
> >
> > Ah, whoops. I've removed the extraneous `static void` from
> > nvic_handle_irq() and build tested that as part of stm32_defconfig.
> >
> > The updated version is in my irq/handle-domain-irq branch at:
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git
> >
>
> $ cat /proc/interrupts
> CPU0
> 16: 24 nvic_irq 4 Edge mps2-clkevt
> 17: 0 nvic_irq 32 Edge mps2-uart-rx
> 18: 6 nvic_irq 33 Edge mps2-uart-tx
> 19: 0 nvic_irq 47 Edge mps2-uart-overrun
> Err: 0
>
> So if it helps feel free to add my
>
> Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

Thanks!

I've folded that in and uppdated the branch.

> As for TODO, is [1] look something you have been thinking of? IIUC,
> the show stopper is that hwirq is being passed from exception entry
> which retrieved via xPSR (IPSR to be precise). OTOH hwirq also available
> via Interrupt Controller Status Register (ICSR) thus can be used in
> driver itself... I gave [1] a go and it runs fine, yet I admit I might
> be missing something...

I hadn't thought about it in much detail, but that looks good!

I was wondering if we needed something like a
handle_arch_vectored_irq(), but if we can rely on the ICSR that seems
simpler overall. I'm not at all familiar with M-class, so I'm not sure
if there are pitfalls in this area.

Thanks,
Mark.

>
> [1]
>
> ---
> arch/arm/include/asm/v7m.h | 3 ++-
> arch/arm/kernel/entry-v7m.S | 10 +++-------
> drivers/irqchip/Kconfig | 1 +
> drivers/irqchip/irq-nvic.c | 21 +++++----------------
> 4 files changed, 11 insertions(+), 24 deletions(-)
>
> diff --git a/arch/arm/include/asm/v7m.h b/arch/arm/include/asm/v7m.h
> index b1bad30b15d2..f047629887e7 100644
> --- a/arch/arm/include/asm/v7m.h
> +++ b/arch/arm/include/asm/v7m.h
> @@ -13,6 +13,7 @@
> #define V7M_SCB_ICSR_PENDSVSET (1 << 28)
> #define V7M_SCB_ICSR_PENDSVCLR (1 << 27)
> #define V7M_SCB_ICSR_RETTOBASE (1 << 11)
> +#define V7M_SCB_ICSR_VECTACTIVE 0x000001ff
>
> #define V7M_SCB_VTOR 0x08
>
> @@ -38,7 +39,7 @@
> #define V7M_SCB_SHCSR_MEMFAULTENA (1 << 16)
>
> #define V7M_xPSR_FRAMEPTRALIGN 0x00000200
> -#define V7M_xPSR_EXCEPTIONNO 0x000001ff
> +#define V7M_xPSR_EXCEPTIONNO V7M_SCB_ICSR_VECTACTIVE
>
> /*
> * When branching to an address that has bits [31:28] == 0xf an exception return
> diff --git a/arch/arm/kernel/entry-v7m.S b/arch/arm/kernel/entry-v7m.S
> index 2e872a248e31..901c7cd1b1ce 100644
> --- a/arch/arm/kernel/entry-v7m.S
> +++ b/arch/arm/kernel/entry-v7m.S
> @@ -72,14 +72,10 @@ __irq_entry:
> @
> @ Invoke the IRQ handler
> @
> - mrs r0, ipsr
> - ldr r1, =V7M_xPSR_EXCEPTIONNO
> - and r0, r1
> - sub r0, #16
> - mov r1, sp
> + mov r0, sp
> stmdb sp!, {lr}
> - @ routine called with r0 = irq number, r1 = struct pt_regs *
> - bl nvic_handle_irq
> + @ routine called with r0 = struct pt_regs *
> + bl generic_handle_arch_irq
>
> pop {lr}
> @
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index aca7b595c4c7..b59a0bc0cd80 100644
> --- a/drivers/irqchip/Kconfig
> +++ b/drivers/irqchip/Kconfig
> @@ -58,6 +58,7 @@ config ARM_NVIC
> bool
> select IRQ_DOMAIN_HIERARCHY
> select GENERIC_IRQ_CHIP
> + select GENERIC_IRQ_MULTI_HANDLER
>
> config ARM_VIC
> bool
> diff --git a/drivers/irqchip/irq-nvic.c b/drivers/irqchip/irq-nvic.c
> index 63bac3f78863..52ff0ed19f2f 100644
> --- a/drivers/irqchip/irq-nvic.c
> +++ b/drivers/irqchip/irq-nvic.c
> @@ -37,25 +37,13 @@
>
> static struct irq_domain *nvic_irq_domain;
>
> -static void __nvic_handle_irq(irq_hw_number_t hwirq)
> +static void __irq_entry nvic_handle_irq(struct pt_regs *regs)
> {
> - generic_handle_domain_irq(nvic_irq_domain, hwirq);
> -}
> + unsigned long icsr = readl_relaxed(BASEADDR_V7M_SCB + V7M_SCB_ICSR);
> + irq_hw_number_t hwirq = (icsr & V7M_SCB_ICSR_VECTACTIVE) - 16;
>
> -/*
> - * TODO: restructure the ARMv7M entry logic so that this entry logic can live
> - * in arch code.
> - */
> -asmlinkage void __exception_irq_entry
> -nvic_handle_irq(irq_hw_number_t hwirq, struct pt_regs *regs)
> -{
> - struct pt_regs *old_regs;
>
> - irq_enter();
> - old_regs = set_irq_regs(regs);
> - __nvic_handle_irq(hwirq);
> - set_irq_regs(old_regs);
> - irq_exit();
> + generic_handle_domain_irq(nvic_irq_domain, hwirq);
> }
>
> static int nvic_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
> @@ -141,6 +129,7 @@ static int __init nvic_of_init(struct device_node *node,
> for (i = 0; i < irqs; i += 4)
> writel_relaxed(0, nvic_base + NVIC_IPR + i);
>
> + set_handle_irq(nvic_handle_irq);
> return 0;
> }
> IRQCHIP_DECLARE(armv7m_nvic, "arm,armv7m-nvic", nvic_of_init);
>
> > Thanks,
> > Mark.
> >
>