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can: c_can: fix an interrupt thrash issue with c_can driver

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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.

Cc: stable@kernel.org # 2.6.39+
Signed-off-by: AnilKumar Ch <anilkumar@ti.com>
Acked-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
AnilKumar Ch 2012-05-23 17:45:10 +05:30 committed by Marc Kleine-Budde
parent 617caccebe
commit 148c87c89e
2 changed files with 4 additions and 4 deletions
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7
drivers/net/can/c_can/c_can.c
View File

@ -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 */

1
drivers/net/can/c_can/c_can.h
View File

@ -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);