linux-kernel - RE: [PATCH] can: Fix bug in suspend/resume

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Date:	Thu, 13 Nov 2014 10:58:04 +0000
From:	Appana Durga Kedareswara Rao <appana.durga.rao@...inx.com>
To:	Marc Kleine-Budde <mkl@...gutronix.de>,
	"wg@...ndegger.com" <wg@...ndegger.com>,
	Michal Simek <michals@...inx.com>,
	Soren Brinkmann <sorenb@...inx.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>
CC:	"linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH] can: Fix bug in suspend/resume

Hi Marc,

-----Original Message-----
From: Marc Kleine-Budde [mailto:mkl@...gutronix.de]
Sent: Thursday, November 13, 2014 4:16 PM
To: Appana Durga Kedareswara Rao; wg@...ndegger.com; Michal Simek; Soren Brinkmann; grant.likely@...aro.org; robh+dt@...nel.org
Cc: linux-can@...r.kernel.org; netdev@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; devicetree@...r.kernel.org; Appana Durga Kedareswara Rao
Subject: Re: [PATCH] can: Fix bug in suspend/resume

On 11/13/2014 11:15 AM, Marc Kleine-Budde wrote:
> On 11/13/2014 07:58 AM, Kedareswara rao Appana wrote:
>> When accessing the priv structure use container_of instead of dev_get_drvdata.
>
> Why?

The drvdata here is the struct net_device, not the platform device.
Please state this in the commit message.

If I understand the code correct, you can make use of the existing helper function to_platform_device():

http://lxr.free-electrons.com/source/include/linux/platform_device.h#L42

Thanks for the suggestion.
 Will use this macro(to_platform_device)  .

>
>> Enable the clocks in the suspend before accessing the registers of the CAN.
>>
>> Signed-off-by: Kedareswara rao Appana <appanad@...inx.com>
>> ---
>>  drivers/net/can/xilinx_can.c |   20 ++++++++++++++++++--
>>  1 files changed, 18 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/can/xilinx_can.c
>> b/drivers/net/can/xilinx_can.c index 5e8b560..63ef645 100644
>> --- a/drivers/net/can/xilinx_can.c
>> +++ b/drivers/net/can/xilinx_can.c
>> @@ -972,15 +972,30 @@ static const struct net_device_ops xcan_netdev_ops = {
>>   */
>>  static int __maybe_unused xcan_suspend(struct device *dev)  {
>> -    struct platform_device *pdev = dev_get_drvdata(dev);
>> +    struct platform_device *pdev = container_of(dev,
>> +                    struct platform_device, dev);
>>      struct net_device *ndev = platform_get_drvdata(pdev);
>>      struct xcan_priv *priv = netdev_priv(ndev);
>> +    int ret;
>>
>>      if (netif_running(ndev)) {
>>              netif_stop_queue(ndev);
>>              netif_device_detach(ndev);
>>      }
>>
>> +    ret = clk_prepare_enable(priv->can_clk);
>> +    if (ret) {
>> +            dev_err(dev, "unable to enable device clock\n");
>> +            return ret;
>> +    }
>> +
>> +    ret = clk_prepare_enable(priv->bus_clk);
>> +    if (ret) {
>> +            dev_err(dev, "unable to enable bus clock\n");
>> +            clk_disable_unprepare(priv->can_clk);
>> +            return ret;
>> +    }
>
> Now you have clock imbalance. Per suspend/resume cycle the clocks are
> enabled twice, but disabled only once.
>

The clocks are getting disabled and un prepared at the end of the probe.
In the resume the driver is doing register write.
In order to do that register write I have to again enable and prepare the clocks.

Regards,
Kedar.

>> +
>>      priv->write_reg(priv, XCAN_MSR_OFFSET, XCAN_MSR_SLEEP_MASK);
>>      priv->can.state = CAN_STATE_SLEEPING;
>>
>> @@ -999,7 +1014,8 @@ static int __maybe_unused xcan_suspend(struct device *dev)
>>   */
>>  static int __maybe_unused xcan_resume(struct device *dev)  {
>> -    struct platform_device *pdev = dev_get_drvdata(dev);
>> +    struct platform_device *pdev = container_of(dev,
>> +                    struct platform_device, dev);
>>      struct net_device *ndev = platform_get_drvdata(pdev);
>>      struct xcan_priv *priv = netdev_priv(ndev);
>>      int ret;

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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