net/at91_ether: avoid NULL pointer dereference

The at91_ether driver calls macb_mii_init passing a 'struct macb'
structure whose tx_clk member is initialized to 0. However,
macb_handle_link_change() expects tx_clk to be the result of
a call to clk_get, and so IS_ERR(tx_clk) to be true if the clock
is invalid. This causes an oops when booting Linux 3.14 on the
csb637 board. The following changes avoids this.

Signed-off-by: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
---
 drivers/net/ethernet/cadence/at91_ether.c |    3 +++
 1 file changed, 3 insertions(+)

On 06/04/2014 20:37, Gilles Chanteperdrix :
> The at91_ether driver calls macb_mii_init passing a 'struct macb'
> structure whose tx_clk member is initialized to 0. However,
> macb_handle_link_change() expects tx_clk to be the result of
> a call to clk_get, and so IS_ERR(tx_clk) to be true if the clock
> is invalid. This causes an oops when booting Linux 3.14 on the
> csb637 board. The following changes avoids this.
> 
> Signed-off-by: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>

Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>

Thanks for this fix. Bye,

> ---
>  drivers/net/ethernet/cadence/at91_ether.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/ethernet/cadence/at91_ether.c b/drivers/net/ethernet/cadence/at91_ether.c
> index ce75de9..4a79eda 100644
> --- a/drivers/net/ethernet/cadence/at91_ether.c
> +++ b/drivers/net/ethernet/cadence/at91_ether.c
> @@ -342,6 +342,9 @@ static int __init at91ether_probe(struct platform_device *pdev)
>  	}
>  	clk_enable(lp->pclk);
>  
> +	lp->hclk = ERR_PTR(-ENOENT);
> +	lp->tx_clk = ERR_PTR(-ENOENT);
> +
>  	/* Install the interrupt handler */
>  	dev->irq = platform_get_irq(pdev, 0);
>  	res = devm_request_irq(&pdev->dev, dev->irq, at91ether_interrupt, 0, dev->name, dev);
>

From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Date: Sun,  6 Apr 2014 20:37:44 +0200

> The at91_ether driver calls macb_mii_init passing a 'struct macb'
> structure whose tx_clk member is initialized to 0. However,
> macb_handle_link_change() expects tx_clk to be the result of
> a call to clk_get, and so IS_ERR(tx_clk) to be true if the clock
> is invalid. This causes an oops when booting Linux 3.14 on the
> csb637 board. The following changes avoids this.
> 
> Signed-off-by: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>

Applied and queued up for -stable, thanks!
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