netdev - Re: [PATCH v3] can: Convert to runtime

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Date:	Thu, 27 Nov 2014 14:47:41 -0800
From:	Sören Brinkmann <soren.brinkmann@...inx.com>
To:	Marc Kleine-Budde <mkl@...gutronix.de>
CC:	Kedareswara rao Appana <appana.durga.rao@...inx.com>,
	<wg@...ndegger.com>, <michal.simek@...inx.com>,
	<grant.likely@...aro.org>, <robh+dt@...nel.org>,
	<linux-can@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	Kedareswara rao Appana <appanad@...inx.com>
Subject: Re: [PATCH v3] can: Convert to runtime_pm

On Thu, 2014-11-27 at 10:17PM +0100, Marc Kleine-Budde wrote:
> On 11/27/2014 02:08 PM, Kedareswara rao Appana wrote:
> > Instead of enabling/disabling clocks at several locations in the driver,
> > use the runtime_pm framework. This consolidates the actions for
> > runtime PM in the appropriate callbacks and makes the driver more
> > readable and mantainable.
> > 
> > Signed-off-by: Soren Brinkmann <soren.brinkmann@...inx.com>
> > Signed-off-by: Kedareswara rao Appana <appanad@...inx.com>
> > ---
> > Changes for v3:
> >   - Converted the driver to use runtime_pm.
> > Changes for v2:
> >   - Removed the struct platform_device* from suspend/resume
> >     as suggest by Lothar.
> > 
> >  drivers/net/can/xilinx_can.c |  119 +++++++++++++++++++++++++----------------
> >  1 files changed, 72 insertions(+), 47 deletions(-)
> > 
> > diff --git a/drivers/net/can/xilinx_can.c b/drivers/net/can/xilinx_can.c
> > index 8a998e3..1be28ed 100644
> > --- a/drivers/net/can/xilinx_can.c
> > +++ b/drivers/net/can/xilinx_can.c
[...]
> > @@ -1030,7 +1046,10 @@ static int __maybe_unused xcan_resume(struct device *dev)
> >  	return 0;
> >  }
> >  
> > -static SIMPLE_DEV_PM_OPS(xcan_dev_pm_ops, xcan_suspend, xcan_resume);
> > +static const struct dev_pm_ops xcan_dev_pm_ops = {
> > +	SET_SYSTEM_SLEEP_PM_OPS(xcan_suspend, xcan_resume)
> > +	SET_PM_RUNTIME_PM_OPS(xcan_runtime_suspend, xcan_runtime_resume, NULL)
> > +};
> >  
> >  /**
> >   * xcan_probe - Platform registration call
> > @@ -1071,7 +1090,7 @@ static int xcan_probe(struct platform_device *pdev)
> >  		return -ENOMEM;
> >  
> >  	priv = netdev_priv(ndev);
> > -	priv->dev = ndev;
> > +	priv->dev = &pdev->dev;
> >  	priv->can.bittiming_const = &xcan_bittiming_const;
> >  	priv->can.do_set_mode = xcan_do_set_mode;
> >  	priv->can.do_get_berr_counter = xcan_get_berr_counter;
> > @@ -1137,6 +1156,11 @@ static int xcan_probe(struct platform_device *pdev)
> >  
> >  	netif_napi_add(ndev, &priv->napi, xcan_rx_poll, rx_max);
> >  
> > +	pm_runtime_set_active(&pdev->dev);
> > +	pm_runtime_irq_safe(&pdev->dev);
> 
> You use just clock_enable()/disable() in the runtime functions, thus you
> can say they are irq_safe. On the other the the zync grpio driver uses
> "full" prepare_enable/disable_unprepare calls. What's best practice here?

IIRC, the prepare/unprepare functions can sleep. xcan_get_berr_counter
is called from atomic context. So, I think we have to use the
disable/enable functions without the prepare/unprepare.
In the GPIO driver the that problem does not exist.

	Sören
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