From mboxrd@z Thu Jan 1 00:00:00 1970 From: AnilKumar Ch Subject: [PATCH v2 1/4] can: c_can: fix an interrupt thrash issue with c_can driver Date: Thu, 10 May 2012 17:04:14 +0530 Message-ID: <1336649657-4152-2-git-send-email-anilkumar@ti.com> References: <1336649657-4152-1-git-send-email-anilkumar@ti.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from arroyo.ext.ti.com ([192.94.94.40]:57776 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754992Ab2EJLfP (ORCPT ); Thu, 10 May 2012 07:35:15 -0400 In-Reply-To: <1336649657-4152-1-git-send-email-anilkumar@ti.com> Sender: linux-can-owner@vger.kernel.org List-ID: To: wg@grandegger.com, mkl@pengutronix.de, linux-can@vger.kernel.org Cc: anantgole@ti.com, nsekhar@ti.com, AnilKumar Ch 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 --- Changes from v1: - Incorporated Marc's comments on irqstatus usage. 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); -- 1.7.0.4