On 2020-01-14 23:30, Paul Burton wrote:

Hi Jiaxun,

On Mon, Jan 13, 2020 at 06:12:51PM +0800, Jiaxun Yang wrote:

quoted

The eoi opreation in mips_cpu_irq_controller caused chained_irq_enter
falsely consider CPU IP interrupt as a FastEOI type IRQ. So the 
interrupt
won't be masked during in handler. Which might lead to spurious 
interrupt.

Thus we simply remove eoi operation for mips_cpu_irq_controller,

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
 drivers/irqchip/irq-mips-cpu.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/irqchip/irq-mips-cpu.c 

b/drivers/irqchip/irq-mips-cpu.c
index 95d4fd8f7a96..0ad7f1f9a58b 100644

--- a/drivers/irqchip/irq-mips-cpu.c
+++ b/drivers/irqchip/irq-mips-cpu.c

@@ -55,7 +55,6 @@ static struct irq_chip mips_cpu_irq_controller = {
 	.irq_mask	= mask_mips_irq,
 	.irq_mask_ack	= mask_mips_irq,
 	.irq_unmask	= unmask_mips_irq,
-	.irq_eoi	= unmask_mips_irq,
 	.irq_disable	= mask_mips_irq,
 	.irq_enable	= unmask_mips_irq,
 };

This one scares me; something doesn't seem right. The irq_eoi (née eoi)
callback was first added way back in commit 1417836e81c0 ("[MIPS] use
generic_handle_irq, handle_level_irq, handle_percpu_irq"). The commit
message there states that the motivation was to allow use of
handle_percpu_irq(), and indeed handle_percpu_irq() does:

    irq_ack() (ie. mask)
    invoke the handler(s)
    irq_eoi() (ie. unmask)

By removing the irq_eoi callback I don't see how we'd ever unmask the
interrupt again..?

To be completely blunt, the fact that unmask and eoi are implemented the
same way is a clear sign that this is a bit broken.

irq_eoi is used if the irqchip tracks the IRQ life-cycle in HW, and it's
not obvious that this is the case. The fact that ack is also mapped to 
mask
just adds to my feeling...

         M.
-- 
Jazz is not dead. It just smells funny...