linux-kernel - Re: [PATCH v3 01/12] genirq: add IRQF_NO_AUTOEN for request

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Date:   Thu, 28 Jan 2021 20:54:36 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Barry Song <song.bao.hua@...ilicon.com>, dmitry.torokhov@...il.com,
        maz@...nel.org, gregkh@...uxfoundation.org,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     linuxarm@...neuler.org, Barry Song <song.bao.hua@...ilicon.com>
Subject: Re: [PATCH v3 01/12] genirq: add IRQF_NO_AUTOEN for request_irq

Barry,

On Fri, Jan 08 2021 at 11:39, Barry Song wrote:
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index ab8567f32501..2b28314e2572 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -1693,6 +1693,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
>  			irqd_set(&desc->irq_data, IRQD_NO_BALANCING);
>  		}
>  
> +		if (new->flags & IRQF_NO_AUTOEN)
> +			irq_settings_set_noautoen(desc);

If we move this to request time flags, then setting the noautoen bit on
the irq descriptor is pretty pointless. See below.

I rather get rid of the irq_settings magic for NOAUTOEN completely.

Thanks,

        tglx
---
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -61,6 +61,8 @@
  *                interrupt handler after suspending interrupts. For system
  *                wakeup devices users need to implement wakeup detection in
  *                their interrupt handlers.
+ * IRQF_NO_AUTOEN - Don't enable IRQ automatically when users request it. Users
+ *                will enable it explicitly by enable_irq() later.
  */
 #define IRQF_SHARED		0x00000080
 #define IRQF_PROBE_SHARED	0x00000100
@@ -74,6 +76,7 @@
 #define IRQF_NO_THREAD		0x00010000
 #define IRQF_EARLY_RESUME	0x00020000
 #define IRQF_COND_SUSPEND	0x00040000
+#define IRQF_NO_AUTOEN		0x00080000
 
 #define IRQF_TIMER		(__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)
 
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1693,7 +1693,8 @@ static int
 			irqd_set(&desc->irq_data, IRQD_NO_BALANCING);
 		}
 
-		if (irq_settings_can_autoenable(desc)) {
+		if (!(new->flags & IRQF_NO_AUTOEN) &&
+		    irq_settings_can_autoenable(desc)) {
 			irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
 		} else {
 			/*
@@ -2086,10 +2087,15 @@ int request_threaded_irq(unsigned int ir
 	 * which interrupt is which (messes up the interrupt freeing
 	 * logic etc).
 	 *
+	 * Also shared interrupts do not go well with disabling auto enable.
+	 * The sharing interrupt might request it while it's still disabled
+	 * and then wait for interrupts forever.
+	 *
 	 * Also IRQF_COND_SUSPEND only makes sense for shared interrupts and
 	 * it cannot be set along with IRQF_NO_SUSPEND.
 	 */
 	if (((irqflags & IRQF_SHARED) && !dev_id) ||
+	    ((irqflags & IRQF_SHARED) && (irqflags & IRQF_NO_AUTOEN)) ||
 	    (!(irqflags & IRQF_SHARED) && (irqflags & IRQF_COND_SUSPEND)) ||
 	    ((irqflags & IRQF_NO_SUSPEND) && (irqflags & IRQF_COND_SUSPEND)))
 		return -EINVAL;