netdev - Re: [PATCH v3 2/2] can: m_can: add deep Suspend/Resume support

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Date:   Fri, 5 May 2017 14:06:54 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Quentin Schulz <quentin.schulz@...e-electrons.com>,
        wg@...ndegger.com, mario.huettel@....net, socketcan@...tkopp.net
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, alexandre.belloni@...e-electrons.com,
        thomas.petazzoni@...e-electrons.com
Subject: Re: [PATCH v3 2/2] can: m_can: add deep Suspend/Resume support

On 05/05/2017 01:46 PM, Quentin Schulz wrote:
> This adds Power Management deep Suspend/Resume support for Bosch M_CAN
> chip.
> 
> When entering deep sleep, the clocks are gated, the interrupts are
> disabled. When resuming from deep sleep, the chip needs to be
> reinitialized, the clocks ungated and the interrupts enabled.
> 
> Signed-off-by: Quentin Schulz <quentin.schulz@...e-electrons.com>
> ---
> 
> v3:
>  - do not close/reopen the can interface (which was previously done when
>  calling m_can_close), basically do the same routine as in probe but
>  it does not close/open the can device,

much better!

>  - update commit log,
> 
> v2:
>  - fix erroneous commit log,
> 
>  drivers/net/can/m_can/m_can.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index 3f0445440146..0a06690febe2 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -1672,10 +1672,9 @@ static __maybe_unused int m_can_suspend(struct device *dev)
>  	if (netif_running(ndev)) {
>  		netif_stop_queue(ndev);
>  		netif_device_detach(ndev);
> +		m_can_stop(ndev);
>  	}
>  
> -	/* TODO: enter low power */
> -
>  	priv->can.state = CAN_STATE_SLEEPING;
>  
>  	return 0;
> @@ -1686,11 +1685,23 @@ static __maybe_unused int m_can_resume(struct device *dev)
>  	struct net_device *ndev = dev_get_drvdata(dev);
>  	struct m_can_priv *priv = netdev_priv(ndev);
>  
> -	/* TODO: exit low power */
> +	m_can_init_ram(priv);
>  
>  	priv->can.state = CAN_STATE_ERROR_ACTIVE;
>  
>  	if (netif_running(ndev)) {
> +		int ret = clk_prepare_enable(priv->hclk);
> +
> +		if (ret)
> +			return ret;
> +
> +		ret = clk_prepare_enable(priv->cclk);
> +		if (ret) {
> +			clk_disable_unprepare(priv->hclk);
> +			return ret;
> +		}
> +
> +		m_can_start(ndev);

Using m_can_stop() m_can_start() here is the way to go. However, when
looking at this hook we se, that the m_can_start/stop functions are not
symmetric (as they should be). Either move the clock handling to
completely in or out of m_can_start/stop.

>  		netif_device_attach(ndev);
>  		netif_start_queue(ndev);
>  	}
> 

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
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