linux-kernel - Re: [PATCH v5] can: Convert to runtime

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Date:	Tue, 13 Jan 2015 18:17:26 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Sören Brinkmann <soren.brinkmann@...inx.com>
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 v5] can: Convert to runtime_pm

On 01/13/2015 06:08 PM, Sören Brinkmann wrote:
> On Tue, 2015-01-13 at 12:08PM +0100, Marc Kleine-Budde wrote:
>> On 01/12/2015 07:45 PM, Sören Brinkmann wrote:
>>> On Mon, 2015-01-12 at 08:34PM +0530, 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 v5:
>>>>  - Updated with the review comments.
>>>>    Updated the remove fuction to use runtime_pm.
>>>> Chnages for v4:
>>>>  - Updated with the review comments.
>>>> 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 |  157 ++++++++++++++++++++++++++++-------------
>>>>  1 files changed, 107 insertions(+), 50 deletions(-)
>>> [..]
>>>> +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;
>>>> +	u32 isr, status;
>>>>  
>>>>  	ret = clk_enable(priv->bus_clk);
>>>>  	if (ret) {
>>>> @@ -1014,15 +1030,28 @@ static int __maybe_unused xcan_resume(struct device *dev)
>>>>  	ret = clk_enable(priv->can_clk);
>>>>  	if (ret) {
>>>>  		dev_err(dev, "Cannot enable clock.\n");
>>>> -		clk_disable_unprepare(priv->bus_clk);
>>>> +		clk_disable(priv->bus_clk);
>>> [...]
>>>> @@ -1173,12 +1219,23 @@ static int xcan_remove(struct platform_device *pdev)
>>>>  {
>>>>  	struct net_device *ndev = platform_get_drvdata(pdev);
>>>>  	struct xcan_priv *priv = netdev_priv(ndev);
>>>> +	int ret;
>>>> +
>>>> +	ret = pm_runtime_get_sync(&pdev->dev);
>>>> +	if (ret < 0) {
>>>> +		netdev_err(ndev, "%s: pm_runtime_get failed(%d)\n",
>>>> +				__func__, ret);
>>>> +		return ret;
>>>> +	}
>>>>  
>>>>  	if (set_reset_mode(ndev) < 0)
>>>>  		netdev_err(ndev, "mode resetting failed!\n");
>>>>  
>>>>  	unregister_candev(ndev);
>>>> +	pm_runtime_disable(&pdev->dev);
>>>>  	netif_napi_del(&priv->napi);
>>>> +	clk_disable_unprepare(priv->bus_clk);
>>>> +	clk_disable_unprepare(priv->can_clk);
>>>
>>> Shouldn't pretty much all these occurrences of clk_disable/enable
>>> disappear? This should all be handled by the runtime_pm framework now.
>>
>> We have:
>> - clk_prepare_enable() in probe
> 
> This should become something like pm_runtime_get_sync(), shouldn't it?
> 
>> - clk_disable_unprepare() in remove
> 
> pm_runtime_put()
> 
>> - clk_enable() in runtime_resume
>> - clk_disable() in runtime_suspend
> 
> These are the ones needed.
> 
> The above makes me suspect that the clocks are always on, regardless of

Define "on" :)
The clocks are prepared after probe() exists, but not enabled. The first
pm_runtime_get_sync() will enable the clocks.

> the runtime suspend state since they are enabled in probe and disabled
> in remove, is that right? Ideally, the usage in probe and remove should
> be migrated to runtime_pm and clocks should really only be running when
> needed and not throughout the whole lifetime of the driver.

The clocks are not en/disabled via pm_runtime, because
pm_runtime_get_sync() is called from atomic contect. We can have another
look into the driver and try to change this.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


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