linux-kernel - Re: [PATCH] irqchip: xilinx: Enable generic irq multi handler

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Date:   Thu, 03 Mar 2022 17:24:02 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Michal Simek <michal.simek@...inx.com>
Cc:     linux-kernel@...r.kernel.org, monstr@...str.eu, git@...inx.com,
        Robert Hancock <robert.hancock@...ian.com>,
        Stefan Asserhall <stefan.asserhall@...inx.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] irqchip: xilinx: Enable generic irq multi handler

On Thu, 03 Mar 2022 16:11:39 +0000,
Michal Simek <michal.simek@...inx.com> wrote:
> 
> Register default arch handler via driver instead of directly pointing to
> xilinx intc controller. This patch makes architecture code more generic.
> 
> Signed-off-by: Michal Simek <michal.simek@...inx.com>
> Reviewed-by: Stefan Asserhall <stefan.asserhall@...inx.com>
> ---
> 
>  arch/microblaze/Kconfig           |  2 ++
>  arch/microblaze/include/asm/irq.h |  3 ---
>  arch/microblaze/kernel/irq.c      | 16 +---------------
>  drivers/irqchip/irq-xilinx-intc.c | 22 +++++++++++++++++++++-
>  4 files changed, 24 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
> index 59798e43cdb0..da568e981604 100644
> --- a/arch/microblaze/Kconfig
> +++ b/arch/microblaze/Kconfig
> @@ -45,6 +45,8 @@ config MICROBLAZE
>  	select SET_FS
>  	select ZONE_DMA
>  	select TRACE_IRQFLAGS_SUPPORT
> +	select GENERIC_IRQ_MULTI_HANDLER
> +	select HANDLE_DOMAIN_IRQ
>  
>  # Endianness selection
>  choice
> diff --git a/arch/microblaze/include/asm/irq.h b/arch/microblaze/include/asm/irq.h
> index 0a28e80bbab0..cb6ab55d1d01 100644
> --- a/arch/microblaze/include/asm/irq.h
> +++ b/arch/microblaze/include/asm/irq.h
> @@ -11,7 +11,4 @@
>  struct pt_regs;
>  extern void do_IRQ(struct pt_regs *regs);
>  
> -/* should be defined in each interrupt controller driver */
> -extern unsigned int xintc_get_irq(void);
> -
>  #endif /* _ASM_MICROBLAZE_IRQ_H */
> diff --git a/arch/microblaze/kernel/irq.c b/arch/microblaze/kernel/irq.c
> index 903dad822fad..1f8cb4c4f74f 100644
> --- a/arch/microblaze/kernel/irq.c
> +++ b/arch/microblaze/kernel/irq.c
> @@ -20,27 +20,13 @@
>  #include <linux/irqchip.h>
>  #include <linux/of_irq.h>
>  
> -static u32 concurrent_irq;
> -
>  void __irq_entry do_IRQ(struct pt_regs *regs)
>  {
> -	unsigned int irq;
>  	struct pt_regs *old_regs = set_irq_regs(regs);
>  	trace_hardirqs_off();
>  
>  	irq_enter();
> -	irq = xintc_get_irq();
> -next_irq:
> -	BUG_ON(!irq);
> -	generic_handle_irq(irq);
> -
> -	irq = xintc_get_irq();
> -	if (irq != -1U) {
> -		pr_debug("next irq: %d\n", irq);
> -		++concurrent_irq;
> -		goto next_irq;
> -	}
> -
> +	handle_arch_irq(regs);
>  	irq_exit();
>  	set_irq_regs(old_regs);
>  	trace_hardirqs_on();
> diff --git a/drivers/irqchip/irq-xilinx-intc.c b/drivers/irqchip/irq-xilinx-intc.c
> index 356a59755d63..c6710190c152 100644
> --- a/drivers/irqchip/irq-xilinx-intc.c
> +++ b/drivers/irqchip/irq-xilinx-intc.c
> @@ -110,7 +110,7 @@ static struct irq_chip intc_dev = {
>  	.irq_mask_ack = intc_mask_ack,
>  };
>  
> -unsigned int xintc_get_irq(void)
> +static unsigned int xintc_get_irq(void)
>  {
>  	unsigned int irq = -1;
>  	u32 hwirq;
> @@ -164,6 +164,25 @@ static void xil_intc_irq_handler(struct irq_desc *desc)
>  	chained_irq_exit(chip, desc);
>  }
>  
> +static u32 concurrent_irq;

Please kill this. It serves no purpose at all.

> +
> +static void xil_intc_handle_irq(struct pt_regs *regs)
> +{
> +	unsigned int irq;
> +
> +	irq = xintc_get_irq();
> +next_irq:
> +	BUG_ON(!irq);
> +	generic_handle_irq(irq);
> +
> +	irq = xintc_get_irq();
> +	if (irq != -1U) {
> +		pr_debug("next irq: %d\n", irq);
> +		++concurrent_irq;
> +		goto next_irq;
> +	}

How about writing this in (basic) C code, and use the exiting APIs?

diff --git a/drivers/irqchip/irq-xilinx-intc.c b/drivers/irqchip/irq-xilinx-intc.c
index 356a59755d63..18125bb841b2 100644
--- a/drivers/irqchip/irq-xilinx-intc.c
+++ b/drivers/irqchip/irq-xilinx-intc.c
@@ -110,18 +110,19 @@ static struct irq_chip intc_dev = {
 	.irq_mask_ack = intc_mask_ack,
 };
 
-unsigned int xintc_get_irq(void)
+#define SPURIOUS_IRQ	(-1U)
+
+static void xil_intc_handle_irq(struct pt_regs *regs)
 {
-	unsigned int irq = -1;
 	u32 hwirq;
 
-	hwirq = xintc_read(primary_intc, IVR);
-	if (hwirq != -1U)
-		irq = irq_find_mapping(primary_intc->root_domain, hwirq);
-
-	pr_debug("irq-xilinx: hwirq=%d, irq=%d\n", hwirq, irq);
+	do {
+		hwirq = xintc_read(primary_intc, IVR);
+		if (unlikely(hwirq == SPURIOUS_IRQ))
+			break;
 
-	return irq;
+		generic_handle_domain_irq(primary_intc->root_domain, hwirq);
+	} while (true);
 }
 
 static int xintc_map(struct irq_domain *d, unsigned int irq, irq_hw_number_t hw)

	M.

-- 
Without deviation from the norm, progress is not possible.