linux-kernel - Re: [PATCH v3 3/4] can: flexcan: switch on clocks before accessing ecr register

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Date:	Tue, 15 Jul 2014 15:54:26 +0200
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Stefan Agner <stefan@...er.ch>
Cc:	shawn.guo@...escale.com, mkl@...gutronix.de,
	linux-arm-kernel@...ts.infradead.org, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] can: flexcan: switch on clocks before accessing
 ecr register

Hi,

Stefan Agner wrote:
> Reported-by: Ashutosh Singh <ashuleapyear@...il.com>
> Suggested-by: Marc Kleine-Budde <mkl@...gutronix.de>
> [stefan@...er.ch: added return check for clk_enable_prepare]
> 
> Signed-off-by: Stefan Agner <stefan@...er.ch>
> ---
>  drivers/net/can/flexcan.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
> index f425ec2..89745aa 100644
> --- a/drivers/net/can/flexcan.c
> +++ b/drivers/net/can/flexcan.c
> @@ -383,12 +383,26 @@ static int flexcan_get_berr_counter(const struct net_device *dev,
>  {
>  	const struct flexcan_priv *priv = netdev_priv(dev);
>  	struct flexcan_regs __iomem *regs = priv->base;
> -	u32 reg = flexcan_read(&regs->ecr);
> +	u32 reg, err;
> +
> +	err = clk_prepare_enable(priv->clk_ipg);
> +	if (err)
> +		return err;
> +
> +	err = clk_prepare_enable(priv->clk_per);
> +	if (err)
> +		goto out_disable_ipg;
> +
> +	reg = flexcan_read(&regs->ecr);
>  
flexcan_get_berr_counter() may be called from interrupt context and
thus must not call any functions that can sleep.
Compiling the driver with CONFIG_DEBUG_ATOMIC_SLEEP would catch this!


Lothar Waßmann
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