Messages in this thread Patch in this message | | | Date | Sun, 17 Jun 2012 19:00:03 +0100 | From | Ben Hutchings <> | Subject | [ 22/69] can: c_can: fix an interrupt thrash issue with c_can driver |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: AnilKumar Ch <anilkumar@ti.com>
commit 148c87c89e1a8863d3d965179f3ab1a06490569e upstream.
This patch fixes an interrupt thrash issue with c_can driver.
In c_can_isr() function interrupts are disabled and enabled only in c_can_poll() function. c_can_isr() & c_can_poll() both read the irqstatus flag. However, irqstatus is always read as 0 in c_can_poll() because all C_CAN interrupts are disabled in c_can_isr(). This causes all interrupts to be re-enabled in c_can_poll() which in turn causes another interrupt since the event is not really handled. This keeps happening causing a flood of interrupts.
To fix this, read the irqstatus register in isr and use the same cached value in the poll function.
Signed-off-by: AnilKumar Ch <anilkumar@ti.com> Acked-by: Wolfgang Grandegger <wg@grandegger.com> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/net/can/c_can/c_can.c | 7 +++---- drivers/net/can/c_can/c_can.h | 1 + 2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c index 9ac28df..fa01621 100644 --- a/drivers/net/can/c_can/c_can.c +++ b/drivers/net/can/c_can/c_can.c @@ -952,7 +952,7 @@ static int c_can_poll(struct napi_struct *napi, int quota) struct net_device *dev = napi->dev; struct c_can_priv *priv = netdev_priv(dev); - irqstatus = priv->read_reg(priv, &priv->regs->interrupt); + irqstatus = priv->irqstatus; if (!irqstatus) goto end; @@ -1030,12 +1030,11 @@ end: static irqreturn_t c_can_isr(int irq, void *dev_id) { - u16 irqstatus; struct net_device *dev = (struct net_device *)dev_id; struct c_can_priv *priv = netdev_priv(dev); - irqstatus = priv->read_reg(priv, &priv->regs->interrupt); - if (!irqstatus) + priv->irqstatus = priv->read_reg(priv, &priv->regs->interrupt); + if (!priv->irqstatus) return IRQ_NONE; /* disable all interrupts and schedule the NAPI */ diff --git a/drivers/net/can/c_can/c_can.h b/drivers/net/can/c_can/c_can.h index 9b7fbef..5f32d34 100644 --- a/drivers/net/can/c_can/c_can.h +++ b/drivers/net/can/c_can/c_can.h @@ -76,6 +76,7 @@ struct c_can_priv { unsigned int tx_next; unsigned int tx_echo; void *priv; /* for board-specific data */ + u16 irqstatus; }; struct net_device *alloc_c_can_dev(void);
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