linux-kernel - [PATCH] rapidio/tsi721: fix bug in MSI interrupt handling

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Date:	Wed,  8 May 2013 09:31:47 -0400
From:	Alexandre Bounine <alexandre.bounine@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Cc:	Alexandre Bounine <alexandre.bounine@....com>,
	Matt Porter <mporter@...nel.crashing.org>
Subject: [PATCH] rapidio/tsi721: fix bug in MSI interrupt handling

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@....com>
Cc: Matt Porter <mporter@...nel.crashing.org>
---
 drivers/rapidio/devices/tsi721.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

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;
 }
 
-- 
1.7.8.4

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