Re: [PATCH v4] MIPS: Replace setup_irq() by request_irq()

On Wed, Mar 11, 2020 at 06:42:10PM +0530, afzal mohammed wrote:

Hi Thomas,

On Wed, Mar 11, 2020 at 11:42:17AM +0100, Thomas Bogendoerfer wrote:

quoted

On Wed, Mar 11, 2020 at 02:33:08PM +0530, afzal mohammed wrote:

quoted

quoted

diff --git a/arch/mips/kernel/cevt-r4k.c b/arch/mips/kernel/cevt-r4k.c

quoted

quoted

 int r4k_clockevent_init(void)
 {
-	unsigned long flags = IRQF_PERCPU | IRQF_TIMER | IRQF_SHARED;
+	unsigned long flags = IRQF_PERCPU | IRQF_TIMER;

quoted

I don't see why this should help. In my tree only sgi-ip30 removes
IRQF_SHARED from flags, but then it uses setup_percpu_irq().
What do I miss ?

You did not miss anything. Though it works, i took a wrong route
following the tags & arrived at that solution in a hurry.
(struct irqaction used in sgi-ip30 was used here earlier w/ setup_irq).

The problem is sanity checks in request_irq() [ rather in
request_thread_iq() ]


	if (((irqflags & IRQF_SHARED) && !dev_id) ||
	    (!(irqflags & IRQF_SHARED) && (irqflags & IRQF_COND_SUSPEND)) ||
	    ((irqflags & IRQF_NO_SUSPEND) && (irqflags & IRQF_COND_SUSPEND)))
		return -EINVAL;

If IRQF_SHARED is passed, it exepcts a non-NULL dev_id, here it is
NULL, setup_irq() doesn't have any check like that.

so request_irq() is not a 1:1 replacement for our current setup_irq().
Or put it the another way our setup_irq() might be buggy, when used for
shared interrupts.

So i think proper solution is to add a non NULL dev_id, as removing
IRQF_SHARED might affect some platforms that might be using that
interrupt line shared.

Patch with non-NULL dev_id below, it works w/ Nathan's test case.

I'm not sure, I like the adding of string pointers as dev_id arguments
in your patch. How can we make sure they are unique enough for the use
case ? I guess using handler as dev_id does a better job here.

And before doing that, lets clean up some of the IRQF_SHARED usage first.
All sni IRQF_SHARED can go away, the interrupt lines are exclusive there. 

loongson2ef/lemote-2f/irq.c: looks like the only user of
LOONGSON_NORTH_BRIDGE_IRQ, so IRQF_SHARED could go as well.
Could someone confirm that ?

All other need to stay, IMHO.

And v4 is already in mips-next, so I need an incremental patch please.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel