[PATCH 49/75] rapidio/tsi721: fix bug in MSI interrupt handling

[Kamal Mostafa]

3.8.13.2 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alexandre Bounine <alexandre.bounine at idt.com>

commit 1ccc819da6fda9bee10ab8b72e9adbb5ad3e4959 upstream.

Fix bug in MSI interrupt handling which causes loss of event
notifications.

Typical indication of lost MSI interrupts are stalled message and
doorbell transfers between RapidIO endpoints.  To avoid loss of MSI
interrupts all interrupts from the device must be disabled on entering
the interrupt handler routine and re-enabled when exiting it.
Re-enabling device interrupts will trigger new MSI message(s) if Tsi721
registered new events since entering interrupt handler routine.

This patch is applicable to kernel versions starting from v3.2.

Signed-off-by: Alexandre Bounine <alexandre.bounine at idt.com>
Cc: Matt Porter <mporter at kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/rapidio/devices/tsi721.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/rapidio/devices/tsi721.c b/drivers/rapidio/devices/tsi721.c
index 6faba40..a8b2c23 100644
--- a/drivers/rapidio/devices/tsi721.c
+++ b/drivers/rapidio/devices/tsi721.c
@@ -471,6 +471,10 @@ static irqreturn_t tsi721_irqhandler(int irq, void *ptr)
 	u32 intval;
 	u32 ch_inte;
 
+	/* For MSI mode disable all device-level interrupts */
+	if (priv->flags & TSI721_USING_MSI)
+		iowrite32(0, priv->regs + TSI721_DEV_INTE);
+
 	dev_int = ioread32(priv->regs + TSI721_DEV_INT);
 	if (!dev_int)
 		return IRQ_NONE;
@@ -560,6 +564,14 @@ static irqreturn_t tsi721_irqhandler(int irq, void *ptr)
 		}
 	}
 #endif
+
+	/* For MSI mode re-enable device-level interrupts */
+	if (priv->flags & TSI721_USING_MSI) {
+		dev_int = TSI721_DEV_INT_SR2PC_CH | TSI721_DEV_INT_SRIO |
+			TSI721_DEV_INT_SMSG_CH | TSI721_DEV_INT_BDMA_CH;
+		iowrite32(dev_int, priv->regs + TSI721_DEV_INTE);
+	}
+
 	return IRQ_HANDLED;
 }
 
-- 
1.8.1.2