[v2] net: fec: Fix the disabling of RX interrupt

On Mon, Feb 18, 2013 at 10:54 PM, Frank Li <lznuaa@gmail.com> wrote:

> This is not correct fix.
> Read, OR and write is not atomic. Need lock.
> But if use hw_lock, it cause dead lock.
> I spend some time to remove such lock.

Ok, could you please try the patch below? It avoids the kernel crash
on my mx53qsb:

 drivers/net/ethernet/freescale/fec.c |   23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

2013/2/19 Fabio Estevam <festevam@gmail.com>:
> On Mon, Feb 18, 2013 at 10:54 PM, Frank Li <lznuaa@gmail.com> wrote:
>
>> This is not correct fix.
>> Read, OR and write is not atomic. Need lock.
>> But if use hw_lock, it cause dead lock.
>> I spend some time to remove such lock.
>
> Ok, could you please try the patch below? It avoids the kernel crash
> on my mx53qsb:

This is similar with my first implement.
It just protect irq and init function. Many place write FEC_IMASK directly.

>
>  drivers/net/ethernet/freescale/fec.c |   23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/fec.c
> b/drivers/net/ethernet/freescale/fec.c
> index 0fe68c4..4df6518 100644
> --- a/drivers/net/ethernet/freescale/fec.c
> +++ b/drivers/net/ethernet/freescale/fec.c
> @@ -804,6 +804,24 @@ rx_processing_done:
>         return pkt_received;
>  }
>
> +static void fec_control_rx(struct net_device *ndev, bool enable)
> +{
> +       struct fec_enet_private *fep = netdev_priv(ndev);
> +       int reg;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&fep->hw_lock, flags);
> +       reg = readl(fep->hwp + FEC_IMASK);
> +       if (enable)
> +               reg |= FEC_ENET_RXF;
> +       else
> +               reg &= ~FEC_ENET_RXF;
> +
> +       writel(reg, fep->hwp + FEC_IMASK);
> +
> +       spin_unlock_irqrestore(&fep->hw_lock, flags);
> +}
> +
>  static irqreturn_t
>  fec_enet_interrupt(int irq, void *dev_id)
>  {
> @@ -821,8 +839,7 @@ fec_enet_interrupt(int irq, void *dev_id)
>
>                         /* Disable the RX interrupt */
>                         if (napi_schedule_prep(&fep->napi)) {
> -                               writel(FEC_RX_DISABLED_IMASK,
> -                                       fep->hwp + FEC_IMASK);
> +                               fec_control_rx(ndev, false);
>                                 __napi_schedule(&fep->napi);
>                         }
>                 }
> @@ -1628,7 +1645,7 @@ static int fec_enet_init(struct net_device *ndev)
>         ndev->netdev_ops = &fec_netdev_ops;
>         ndev->ethtool_ops = &fec_enet_ethtool_ops;
>
> -       writel(FEC_RX_DISABLED_IMASK, fep->hwp + FEC_IMASK);
> +       fec_control_rx(ndev, false);

I think this issue was caused by enable irq before register irq handler.
writel(0, fep->hwp + FEC_IMASK) should fix mx53's problem.

best regards
Frank Li

>         netif_napi_add(ndev, &fep->napi, fec_enet_rx_napi, FEC_NAPI_WEIGHT);
>
>         /* Initialize the receive buffer descriptors. */
> --
> 1.7.9.5
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On Mon, Feb 18, 2013 at 11:47 PM, Frank Li <lznuaa@gmail.com> wrote:

> This is similar with my first implement.

I checked your original implementation and
spin_lock_irqsave/spin_unlock_irqrestore was very far apart.

> It just protect irq and init function. Many place write FEC_IMASK directly.

Yes, but the main issue with current code is that it does not clear
the only rx irq as it should.

> I think this issue was caused by enable irq before register irq handler.
> writel(0, fep->hwp + FEC_IMASK) should fix mx53's problem.

No, it does not solve the issue.

I don't have a mx6q board handy. If you could try this patch and let
me know if you see any deadlock, it would be nice.

Thanks,

Fabio Estevam
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2013/2/19 Fabio Estevam <festevam@gmail.com>:
> On Mon, Feb 18, 2013 at 11:47 PM, Frank Li <lznuaa@gmail.com> wrote:
>
>> This is similar with my first implement.
>
> I checked your original implementation and
> spin_lock_irqsave/spin_unlock_irqrestore was very far apart.
>
>> It just protect irq and init function. Many place write FEC_IMASK directly.
>
> Yes, but the main issue with current code is that it does not clear
> the only rx irq as it should.

The key is Read OR and write need lock.
I try reduce FEC lock.

FEC_IMASK should be two state,
one is FEC_DEFAULT_IMASK, the other is FEC_RX_DISABLED_IMASK.
FEC_RX_DISABLED_IMASK is equal as clean rx irq only.

I will found mx53 to found the real root cause

>
>> I think this issue was caused by enable irq before register irq handler.
>> writel(0, fep->hwp + FEC_IMASK) should fix mx53's problem.
>
> No, it does not solve the issue.
>
> I don't have a mx6q board handy. If you could try this patch and let
> me know if you see any deadlock, it would be nice.
>
> Thanks,
>
> Fabio Estevam
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