Subject: Re: [PATCH v3] can: Convert to runtime_pm

From: Marc Kleine-Budde <[email-masked]>
Date: Thu, 27 Nov 2014 22:17:53 +0100

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 <[email-masked]>
> Signed-off-by: Kedareswara rao Appana <[email-masked]>
> ---
> 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
> @@ -32,6 +32,7 @@
>  #include <linux/can/dev.h>
>  #include <linux/can/error.h>
>  #include <linux/can/led.h>
> +#include <linux/pm_runtime.h>
>  
>  #define DRIVER_NAME	"xilinx_can"
>  
> @@ -138,7 +139,7 @@ struct xcan_priv {
>  	u32 (*read_reg)(const struct xcan_priv *priv, enum xcan_reg reg);
>  	void (*write_reg)(const struct xcan_priv *priv, enum xcan_reg reg,
>  			u32 val);
> -	struct net_device *dev;
> +	struct device *dev;
>  	void __iomem *reg_base;
>  	unsigned long irq_flags;
>  	struct clk *bus_clk;
> @@ -842,6 +843,13 @@ static int xcan_open(struct net_device *ndev)
>  	struct xcan_priv *priv = netdev_priv(ndev);
>  	int ret;
>  
> +	ret = pm_runtime_get_sync(priv->dev);
> +	if (ret < 0) {
> +		netdev_err(ndev, "%s: runtime CAN resume failed(%d)\n\r",
> +				__func__, ret);
> +		return ret;
> +	}
> +
>  	ret = request_irq(ndev->irq, xcan_interrupt, priv->irq_flags,
>  			ndev->name, ndev);
>  	if (ret < 0) {
> @@ -849,29 +857,17 @@ static int xcan_open(struct net_device *ndev)
>  		goto err;
>  	}
>  
> -	ret = clk_prepare_enable(priv->can_clk);
> -	if (ret) {
> -		netdev_err(ndev, "unable to enable device clock\n");
> -		goto err_irq;
> -	}
> -
> -	ret = clk_prepare_enable(priv->bus_clk);
> -	if (ret) {
> -		netdev_err(ndev, "unable to enable bus clock\n");
> -		goto err_can_clk;
> -	}
> -
>  	/* Set chip into reset mode */
>  	ret = set_reset_mode(ndev);
>  	if (ret < 0) {
>  		netdev_err(ndev, "mode resetting failed!\n");
> -		goto err_bus_clk;
> +		goto err_irq;
>  	}
>  
>  	/* Common open */
>  	ret = open_candev(ndev);
>  	if (ret)
> -		goto err_bus_clk;
> +		goto err_irq;
>  
>  	ret = xcan_chip_start(ndev);
>  	if (ret < 0) {
> @@ -887,13 +883,11 @@ static int xcan_open(struct net_device *ndev)
>  
>  err_candev:
>  	close_candev(ndev);
> -err_bus_clk:
> -	clk_disable_unprepare(priv->bus_clk);
> -err_can_clk:
> -	clk_disable_unprepare(priv->can_clk);
>  err_irq:
>  	free_irq(ndev->irq, ndev);
>  err:
> +	pm_runtime_put(priv->dev);
> +
>  	return ret;
>  }
>  
> @@ -910,12 +904,11 @@ static int xcan_close(struct net_device *ndev)
>  	netif_stop_queue(ndev);
>  	napi_disable(&priv->napi);
>  	xcan_chip_stop(ndev);
> -	clk_disable_unprepare(priv->bus_clk);
> -	clk_disable_unprepare(priv->can_clk);
>  	free_irq(ndev->irq, ndev);
>  	close_candev(ndev);
>  
>  	can_led_event(ndev, CAN_LED_EVENT_STOP);
> +	pm_runtime_put(priv->dev);
>  
>  	return 0;
>  }
> @@ -934,27 +927,21 @@ static int xcan_get_berr_counter(const struct net_device *ndev,
>  	struct xcan_priv *priv = netdev_priv(ndev);
>  	int ret;
>  
> -	ret = clk_prepare_enable(priv->can_clk);
> -	if (ret)
> -		goto err;
> +	ret = pm_runtime_get_sync(priv->dev);
> +	if (ret < 0) {
> +		netdev_err(ndev, "%s: runtime resume failed(%d)\n\r",
> +				__func__, ret);
> +		return ret;
> +	}
>  
> -	ret = clk_prepare_enable(priv->bus_clk);
> -	if (ret)
> -		goto err_clk;
>  
>  	bec->txerr = priv->read_reg(priv, XCAN_ECR_OFFSET) & XCAN_ECR_TEC_MASK;
>  	bec->rxerr = ((priv->read_reg(priv, XCAN_ECR_OFFSET) &
>  			XCAN_ECR_REC_MASK) >> XCAN_ESR_REC_SHIFT);
>  
> -	clk_disable_unprepare(priv->bus_clk);
> -	clk_disable_unprepare(priv->can_clk);
> +	pm_runtime_put(priv->dev);
>  
>  	return 0;
> -
> -err_clk:
> -	clk_disable_unprepare(priv->can_clk);
> -err:
> -	return ret;
>  }
>  
>  
> @@ -967,15 +954,45 @@ static const struct net_device_ops xcan_netdev_ops = {
>  
>  /**
>   * xcan_suspend - Suspend method for the driver
> - * @dev:	Address of the platform_device structure
> + * @dev:	Address of the net_device structure
>   *
>   * Put the driver into low power mode.
> - * Return: 0 always
> + * Return: 0 on success and failure value on error
>   */
>  static int __maybe_unused xcan_suspend(struct device *dev)
>  {
> -	struct platform_device *pdev = dev_get_drvdata(dev);
> -	struct net_device *ndev = platform_get_drvdata(pdev);
> +	if (!device_may_wakeup(dev))
> +		return pm_runtime_force_suspend(dev);
> +
> +	return 0;
> +}
> +
> +/**
> + * xcan_resume - Resume from suspend
> + * @dev:	Address of the net_device structure
> + *
> + * Resume operation after suspend.
> + * Return: 0 on success and failure value on error
> + */
> +static int __maybe_unused xcan_resume(struct device *dev)
> +{
> +	if (!device_may_wakeup(dev))
> +		return pm_runtime_force_resume(dev);
> +
> +	return 0;
> +
> +}
> +
> +/**
> + * xcan_runtime_suspend - Runtime suspend method for the driver
> + * @dev:	Address of the net_device structure
> + *
> + * Put the driver into low power mode.
> + * Return: 0 always
> + */
> +static int __maybe_unused xcan_runtime_suspend(struct device *dev)
> +{
> +	struct net_device *ndev = dev_get_drvdata(dev);
>  	struct xcan_priv *priv = netdev_priv(ndev);
>  
>  	if (netif_running(ndev)) {
> @@ -993,16 +1010,15 @@ static int __maybe_unused xcan_suspend(struct device *dev)
>  }
>  
>  /**
> - * xcan_resume - Resume from suspend
> - * @dev:	Address of the platformdevice structure
> + * xcan_runtime_resume - Runtime resume from suspend
> + * @dev:	Address of the net_device structure
>   *
>   * Resume operation after suspend.
>   * Return: 0 on success and failure value on error
>   */
> -static int __maybe_unused xcan_resume(struct device *dev)
> +static int __maybe_unused xcan_runtime_resume(struct device *dev)
>  {
> -	struct platform_device *pdev = dev_get_drvdata(dev);
> -	struct net_device *ndev = platform_get_drvdata(pdev);
> +	struct net_device *ndev = dev_get_drvdata(dev);
>  	struct xcan_priv *priv = netdev_priv(ndev);
>  	int ret;

...adding the rest of the function to comment it:

> 	ret = clk_enable(priv->bus_clk);
> 	if (ret) {
> 		dev_err(dev, "Cannot enable clock.\n");
> 		return ret;
> 	}
> 	ret = clk_enable(priv->can_clk);
> 	if (ret) {
> 		dev_err(dev, "Cannot enable clock.\n");
> 		clk_disable_unprepare(priv->bus_clk);
> 		return ret;
> 	}
> 
> 	priv->write_reg(priv, XCAN_MSR_OFFSET, 0);
> 	priv->write_reg(priv, XCAN_SRR_OFFSET, XCAN_SRR_CEN_MASK);
> 	priv->can.state = CAN_STATE_ERROR_ACTIVE;

Does it have any side effects, when writing these values when the CAN
device is not UP? (e.g. when running the berr callback?) Setting its
state to ERROR active is probably wrong. Do you have to move it into the
if(netif_running())?

> 	if (netif_running(ndev)) {
> 		netif_device_attach(ndev);
> 		netif_start_queue(ndev);
> 	}
> 
> 	return 0;
> }

>  
> @@ -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?

> +	pm_runtime_enable(&pdev->dev);
> +	pm_runtime_get_sync(&pdev->dev);
> +
>  	ret = register_candev(ndev);
>  	if (ret) {
>  		dev_err(&pdev->dev, "fail to register failed (err=%d)\n", ret);

I think in case of an error, you have to call pm_runtime_put() here

> @@ -1144,8 +1168,9 @@ static int xcan_probe(struct platform_device *pdev)
>  	}
>  
>  	devm_can_led_init(ndev);
> -	clk_disable_unprepare(priv->bus_clk);
> -	clk_disable_unprepare(priv->can_clk);
> +
> +	pm_runtime_put(&pdev->dev);
> +
>  	netdev_dbg(ndev, "reg_base=0x%p irq=%d clock=%d, tx fifo depth:%d\n",
>  			priv->reg_base, ndev->irq, priv->can.clock.freq,
>  			priv->tx_max);
> 

Marc

-- 
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