Re: [PATCH V2 08/15] irqchip: bcm7120-l2: Eliminate bad IRQ check

From: Sergei Shtylyov
Date: Thu Oct 30 2014 - 07:09:32 EST


Hello.

On 10/30/2014 5:18 AM, Kevin Cernekee wrote:

This check may be prone to race conditions, e.g.

1) Some external event (e.g. GPIO level) causes an IRQ to become pending
2) Peripheral asserts the L2 IRQ
3) CPU takes an interrupt
4) The event from #1 goes away
5) bcm7120_l2_intc_irq_handle() reads back a 0 status

Unlike the hardware supported by brcmstb-l2, the bcm7120-l2 controller
does not latch the IRQ status. Bits can change if the inputs to the
controller change. Also, do_bad_IRQ() is an ARM-specific macro.

So let's just nuke it.

Signed-off-by: Kevin Cernekee <cernekee@xxxxxxxxx>
Acked-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
---
drivers/irqchip/irq-bcm7120-l2.c | 9 ---------
1 file changed, 9 deletions(-)

diff --git a/drivers/irqchip/irq-bcm7120-l2.c b/drivers/irqchip/irq-bcm7120-l2.c
index b9f4fb8..49d8f3d 100644
--- a/drivers/irqchip/irq-bcm7120-l2.c
+++ b/drivers/irqchip/irq-bcm7120-l2.c
[...]
@@ -51,19 +49,12 @@ static void bcm7120_l2_intc_irq_handle(unsigned int irq, struct irq_desc *desc)
chained_irq_enter(chip, desc);

status = __raw_readl(b->base + IRQSTAT);
-
- if (status == 0) {
- do_bad_IRQ(irq, desc);
- goto out;
- }
-
do {

I think this needs to now become:

while (status) {

irq = ffs(status) - 1;
status &= ~(1 << irq);

In case 'status' is 0, 'irq' will be equal to -1. How does the shift by negative value work?

generic_handle_irq(irq_find_mapping(b->domain, irq));
} while (status);

WBR, Sergei

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