RE: [PATCH v2 1/2] flexcan: add err_irq handler for flexcan

[qiang.z...@freescale.com]

On Sat, 2014-06-21 at 12:19, Wood Scott wrote:

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Saturday, June 21, 2014 12:19 AM
> To: Zhao Qiang-B45475
> Cc: linuxppc-dev@lists.ozlabs.org; linux-...@vger.kernel.org;
> w...@grandegger.com; m...@pengutronix.de; Wood Scott-B07421
> Subject: Re: [PATCH v2 1/2] flexcan: add err_irq handler for flexcan
> 
> On Fri, 2014-06-20 at 10:01 +0800, Zhao Qiang wrote:
> > when flexcan is not physically linked, command 'cantest' will trigger
> > an err_irq, add err_irq handler for it.
> >
> > Signed-off-by: Zhao Qiang <b45...@freescale.com>
> > ---
> > Changes for v2:
> >     - use a space instead of tab
> >     - use flexcan_poll_state instead of print
> >
> >  drivers/net/can/flexcan.c | 31 ++++++++++++++++++++++++++++++-
> >  1 file changed, 30 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
> > index f425ec2..7432ba4 100644
> > --- a/drivers/net/can/flexcan.c
> > +++ b/drivers/net/can/flexcan.c
> > @@ -208,6 +208,7 @@ struct flexcan_priv {
> >     void __iomem *base;
> >     u32 reg_esr;
> >     u32 reg_ctrl_default;
> > +   unsigned int err_irq;
> 
> Why unsigned?
Err_irq is from 0.
> 
> > +static irqreturn_t flexcan_err_irq(int irq, void *dev_id) {
> > +   struct net_device *dev = dev_id;
> > +   struct flexcan_priv *priv = netdev_priv(dev);
> > +   struct flexcan_regs __iomem *regs = priv->base;
> > +   u32 reg_ctrl, reg_esr;
> > +
> > +   reg_esr = flexcan_read(&regs->esr);
> > +   reg_ctrl = flexcan_read(&regs->ctrl);
> > +   if (reg_esr & FLEXCAN_ESR_TX_WRN) {
> > +           flexcan_write(reg_esr & ~FLEXCAN_ESR_TX_WRN, &regs->esr);
> > +           flexcan_write(reg_ctrl & ~FLEXCAN_CTRL_ERR_MSK, &regs->ctrl);
> > +           flexcan_poll_state(dev, reg_esr);
> > +   }
> > +   return IRQ_HANDLED;
> > +}
> 
> You should only return IRQ_HANDLED if there was something to handle.
> 
> > @@ -944,6 +962,12 @@ static int flexcan_open(struct net_device *dev)
> >     if (err)
> >             goto out_close;
> >
> > +   if (priv->err_irq)
> > +           err = request_irq(priv->err_irq, flexcan_err_irq, IRQF_SHARED,
> > +                             dev->name, dev);
> > +   if (err)
> > +           goto out_close;
> 
> Is this really a fatal error?  And why do you check err outside the "if
> (priv->err_irq)" block?  What if some previous code left err non-zero
> (either now or after some future code change)?
> 
> > @@ -1126,6 +1150,10 @@ static int flexcan_probe(struct platform_device
> *pdev)
> >     if (irq <= 0)
> >             return -ENODEV;
> >
> > +   err_irq = platform_get_irq(pdev, 1);
> > +   if (err_irq <= 0)
> > +           err_irq = 0;
> > +
> 
> Why is this <= 0 check needed?

Interrupt[1] is optional. If there is not interrupt[1] in dtb, err_irq will be 
<=0.

> 
> -Scott
> 

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