Re: [PATCH v9] can: c_can: Add runtime PM support to Bosch C_CAN/D_CAN controller

[Kevin Hilman <khilman@deeprootsystems.com>]

AnilKumar Ch <anilkumar@ti.com> writes:

> Add Runtime PM support to C_CAN/D_CAN controller. The runtime PM
> APIs control clocks for C_CAN/D_CAN IP and prevent access to the
> register of C_CAN/D_CAN IP when clock is turned off.
>
> Signed-off-by: AnilKumar Ch <anilkumar@ti.com>

I'm not familar with the CAN specifics here, but some comments on the
runtime PM implementation.

> ---
> This patch has been tested on AM335X EVM. Due to lack of hardware
> I am not able to test c_can functionality. I appreciate if anyone
> can test c_can functionality with this patch.
>
> This patch is based on "can-next/master" 
>
> Changes from v8:
> 	- corrected the return path sequence in c_can_probe()
>
> Changes from v7:
> 	- Incorporated Marc's comments on v7
> 	  * changed device pointer to c_can_priv pointer
>
> Changes from v6:
> 	- Incorporated Marc's comments on v6
> 	  * changed dev pointer to priv
> 	  * removed platform_device.h include from c_can.c
>
> Changes from v5:
> 	- Incorporated Marc's comments on v5
> 	  * changed runtime pm calls in c_can driver to handle
> 	    the drivers which are not using platform drivers.
> 	  * added device pointer protection in c_can driver if
> 	    not passed from platform/pci driver.
>
> Changes from v4:
> 	- Incorporated Vaibhav H review comments on v4.
> 	  * Moved pm_runtime put/get_sync calls to appropriate positions.
> 	- This patch is from "Add DT support to C_CAN/D_CAN controller"
> 	  patch series. Rest of the patches in this series were applied
> 	  so this v5 contains only this patch.
>
>  drivers/net/can/c_can/c_can.c          |   24 +++++++++++++++++++++++-
>  drivers/net/can/c_can/c_can.h          |    1 +
>  drivers/net/can/c_can/c_can_platform.c |   11 +++++++++--
>  3 files changed, 33 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
> index 4c538e3..966d318 100644
> --- a/drivers/net/can/c_can/c_can.c
> +++ b/drivers/net/can/c_can/c_can.c
> @@ -34,6 +34,7 @@
>  #include <linux/if_ether.h>
>  #include <linux/list.h>
>  #include <linux/io.h>
> +#include <linux/pm_runtime.h>
>  
>  #include <linux/can.h>
>  #include <linux/can/dev.h>
> @@ -201,6 +202,18 @@ static const struct can_bittiming_const c_can_bittiming_const = {
>  	.brp_inc = 1,
>  };
>  
> +static inline void c_can_pm_runtime_get_sync(struct c_can_priv *priv)
> +{
> +	if (priv->device)
> +		pm_runtime_get_sync(priv->device);
> +}
> +
> +static inline void c_can_pm_runtime_put_sync(struct c_can_priv *priv)
> +{
> +	if (priv->device)
> +		pm_runtime_put_sync(priv->device);
> +}

IMO, these extra helpers are rather unsightly, and should not be needed.
The driver should just be directly doing get_sync/put_sync.  If
priv->device isn't presnt, then runtime PM should just never be enabled.

Kevin

>  static inline int get_tx_next_msg_obj(const struct c_can_priv *priv)
>  {
>  	return (priv->tx_next & C_CAN_NEXT_MSG_OBJ_MASK) +
> @@ -673,11 +686,15 @@ static int c_can_get_berr_counter(const struct net_device *dev,
>  	unsigned int reg_err_counter;
>  	struct c_can_priv *priv = netdev_priv(dev);
>  
> +	c_can_pm_runtime_get_sync(priv);
> +
>  	reg_err_counter = priv->read_reg(priv, C_CAN_ERR_CNT_REG);
>  	bec->rxerr = (reg_err_counter & ERR_CNT_REC_MASK) >>
>  				ERR_CNT_REC_SHIFT;
>  	bec->txerr = reg_err_counter & ERR_CNT_TEC_MASK;
>  
> +	c_can_pm_runtime_put_sync(priv);
> +
>  	return 0;
>  }
>  
> @@ -1053,11 +1070,13 @@ static int c_can_open(struct net_device *dev)
>  	int err;
>  	struct c_can_priv *priv = netdev_priv(dev);
>  
> +	c_can_pm_runtime_get_sync(priv);
> +
>  	/* open the can device */
>  	err = open_candev(dev);
>  	if (err) {
>  		netdev_err(dev, "failed to open can device\n");
> -		return err;
> +		goto exit_open_fail;
>  	}
>  
>  	/* register interrupt handler */
> @@ -1079,6 +1098,8 @@ static int c_can_open(struct net_device *dev)
>  
>  exit_irq_fail:
>  	close_candev(dev);
> +exit_open_fail:
> +	c_can_pm_runtime_put_sync(priv);
>  	return err;
>  }
>  
> @@ -1091,6 +1112,7 @@ static int c_can_close(struct net_device *dev)
>  	c_can_stop(dev);
>  	free_irq(dev->irq, dev);
>  	close_candev(dev);
> +	c_can_pm_runtime_put_sync(priv);
>  
>  	return 0;
>  }
> diff --git a/drivers/net/can/c_can/c_can.h b/drivers/net/can/c_can/c_can.h
> index 4e56baa..1437a6d 100644
> --- a/drivers/net/can/c_can/c_can.h
> +++ b/drivers/net/can/c_can/c_can.h
> @@ -153,6 +153,7 @@ struct c_can_priv {
>  	struct can_priv can;	/* must be the first member */
>  	struct napi_struct napi;
>  	struct net_device *dev;
> +	struct device *device;
>  	int tx_object;
>  	int current_status;
>  	int last_status;
> diff --git a/drivers/net/can/c_can/c_can_platform.c b/drivers/net/can/c_can/c_can_platform.c
> index d0a66cf..90801c4 100644
> --- a/drivers/net/can/c_can/c_can_platform.c
> +++ b/drivers/net/can/c_can/c_can_platform.c
> @@ -32,6 +32,7 @@
>  #include <linux/clk.h>
>  #include <linux/of.h>
>  #include <linux/of_device.h>
> +#include <linux/pm_runtime.h>
>  
>  #include <linux/can/dev.h>
>  
> @@ -177,8 +178,11 @@ static int __devinit c_can_plat_probe(struct platform_device *pdev)
>  		goto exit_free_device;
>  	}
>  
> +	pm_runtime_enable(&pdev->dev);
> +
>  	dev->irq = irq;
>  	priv->base = addr;
> +	priv->device = &pdev->dev;
>  	priv->can.clock.freq = clk_get_rate(clk);
>  	priv->priv = clk;
>  
> @@ -189,15 +193,17 @@ static int __devinit c_can_plat_probe(struct platform_device *pdev)
>  	if (ret) {
>  		dev_err(&pdev->dev, "registering %s failed (err=%d)\n",
>  			KBUILD_MODNAME, ret);
> -		goto exit_free_device;
> +		goto exit_clear_drvdata;
>  	}
>  
>  	dev_info(&pdev->dev, "%s device registered (regs=%p, irq=%d)\n",
>  		 KBUILD_MODNAME, priv->base, dev->irq);
>  	return 0;
>  
> -exit_free_device:
> +exit_clear_drvdata:
>  	platform_set_drvdata(pdev, NULL);
> +	pm_runtime_disable(&pdev->dev);
> +exit_free_device:
>  	free_c_can_dev(dev);
>  exit_iounmap:
>  	iounmap(addr);
> @@ -226,6 +232,7 @@ static int __devexit c_can_plat_remove(struct platform_device *pdev)
>  	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	release_mem_region(mem->start, resource_size(mem));
>  
> +	pm_runtime_disable(&pdev->dev);
>  	clk_put(priv->priv);
>  
>  	return 0;