45 lines
1.9 KiB
Diff
45 lines
1.9 KiB
Diff
|
From ddda6fa410b6e50ee67d4a628187e76b4a6c9b28 Mon Sep 17 00:00:00 2001
|
||
|
|
From: Lior Amsalem <alior@marvell.com>
|
||
|
|
Date: Mon, 25 Nov 2013 17:26:45 +0100
|
||
|
|
Subject: [PATCH 086/203] irqchip: armada-370-xp: fix MSI race condition
|
||
|
|
|
||
|
|
In the Armada 370/XP driver, when we receive an IRQ 1, we read the
|
||
|
|
list of doorbells that caused the interrupt from register
|
||
|
|
ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS. This gives the list of MSIs that
|
||
|
|
were generated. However, instead of acknowledging only the MSIs that
|
||
|
|
were generated, we acknowledge *all* the MSIs, by writing
|
||
|
|
~MSI_DOORBELL_MASK in the ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS register.
|
||
|
|
|
||
|
|
This creates a race condition: if a new MSI that isn't part of the
|
||
|
|
ones read into the temporary "msimask" variable is fired before we
|
||
|
|
acknowledge all MSIs, then we will simply loose it.
|
||
|
|
|
||
|
|
It is important to mention that this ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS
|
||
|
|
register has the following behavior: "A CPU write of 0 clears the bits
|
||
|
|
in this field. A CPU write of 1 has no effect". This is what allows us
|
||
|
|
to simply write ~msimask to acknoledge the handled MSIs.
|
||
|
|
|
||
|
|
Notice that the same problem is present in the IPI implementation, but
|
||
|
|
it is fixed as a separate patch, so that this IPI fix can be pushed to
|
||
|
|
older stable versions as appropriate (all the way to 3.8), while the
|
||
|
|
MSI code only appeared in 3.13.
|
||
|
|
|
||
|
|
Signed-off-by: Lior Amsalem <alior@marvell.com>
|
||
|
|
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
|
||
|
|
Cc: Thomas Gleixner <tglx@linutronix.de>
|
||
|
|
---
|
||
|
|
drivers/irqchip/irq-armada-370-xp.c | 2 +-
|
||
|
|
1 file changed, 1 insertion(+), 1 deletion(-)
|
||
|
|
|
||
|
|
--- a/drivers/irqchip/irq-armada-370-xp.c
|
||
|
|
+++ b/drivers/irqchip/irq-armada-370-xp.c
|
||
|
|
@@ -381,7 +381,7 @@ armada_370_xp_handle_irq(struct pt_regs
|
||
|
|
ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS)
|
||
|
|
& PCI_MSI_DOORBELL_MASK;
|
||
|
|
|
||
|
|
- writel(~PCI_MSI_DOORBELL_MASK, per_cpu_int_base +
|
||
|
|
+ writel(~msimask, per_cpu_int_base +
|
||
|
|
ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS);
|
||
|
|
|
||
|
|
for (msinr = PCI_MSI_DOORBELL_START;
|