netdev - Re: [v2,3/3] can: m_can: Add PM Runtime

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Date:   Wed, 20 Sep 2017 19:36:15 -0500
From:   Franklin S Cooper Jr <fcooper@...com>
To:     Sekhar Nori <nsekhar@...com>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-can@...r.kernel.org>, <wg@...ndegger.com>,
        <mkl@...gutronix.de>, <robh+dt@...nel.org>,
        <quentin.schulz@...e-electrons.com>
CC:     Linux OMAP List <linux-omap@...r.kernel.org>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Wenyou Yang <wenyou.yang@...el.com>,
        Mario Hüttel <mario.huettel@....net>
Subject: Re: [v2,3/3] can: m_can: Add PM Runtime


On 08/24/2017 03:30 AM, Sekhar Nori wrote:
> + OMAP mailing list
> 
> On Tuesday 25 July 2017 04:21 AM, Franklin Cooper wrote:
>> Add support for PM Runtime which is the new way to handle managing clocks.
>> However, to avoid breaking SoCs not using PM_RUNTIME leave the old clk
>> management approach in place.
> 
> Since hclk is the interface clock, I think at a minimum there needs to
> be an assumption that pm_runtime_get_sync() will enable that clock and
> make the module ready for access.
> 
> The only in-kernel user of this driver seems to be an atmel SoC. I am
> ccing folks who added support for M_CAN on that SoC to see if hclk
> management can be left to pm_runtime*() on their SoC.
> 
> If they are okay, I think its a good to atleast drop explicit hclk
> enable disable in the driver. That way, we avoid double enable/disable
> of interface clock (hclk).

Wenyou,

Do you foresee this being a problem on your board? If not I can send a
v3 removing these clk_enable and clk_disable calls and it would be great
if you can test it out and provide your tested by.

> 
>>
>> PM_RUNTIME is required by OMAP based devices to handle clock management.
>> Therefore, this allows future Texas Instruments SoCs that have the MCAN IP
>> to work with this driver.
>>
>> Signed-off-by: Franklin S Cooper Jr <fcooper@...com>
> 
> Thanks,
> Sekhar
> 
>> ---
>>  drivers/net/can/m_can/m_can.c | 13 +++++++++++++
>>  1 file changed, 13 insertions(+)
>>
>> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
>> index ea48e59..93e23f5 100644
>> --- a/drivers/net/can/m_can/m_can.c
>> +++ b/drivers/net/can/m_can/m_can.c
>> @@ -23,6 +23,7 @@
>>  #include <linux/of.h>
>>  #include <linux/of_device.h>
>>  #include <linux/platform_device.h>
>> +#include <linux/pm_runtime.h>
>>  #include <linux/iopoll.h>
>>  #include <linux/can/dev.h>
>>  
>> @@ -633,11 +634,15 @@ static int m_can_clk_start(struct m_can_priv *priv)
>>  	if (err)
>>  		clk_disable_unprepare(priv->hclk);
>>  
>> +	pm_runtime_get_sync(priv->device);
>> +
>>  	return err;
>>  }
>>  
>>  static void m_can_clk_stop(struct m_can_priv *priv)
>>  {
>> +	pm_runtime_put_sync(priv->device);
>> +
>>  	clk_disable_unprepare(priv->cclk);
>>  	clk_disable_unprepare(priv->hclk);
>>  }
>> @@ -1582,6 +1587,8 @@ static int m_can_plat_probe(struct platform_device *pdev)
>>  	/* Enable clocks. Necessary to read Core Release in order to determine
>>  	 * M_CAN version
>>  	 */
>> +	pm_runtime_enable(&pdev->dev);
>> +
>>  	ret = clk_prepare_enable(hclk);
>>  	if (ret)
>>  		goto disable_hclk_ret;
>> @@ -1626,6 +1633,8 @@ static int m_can_plat_probe(struct platform_device *pdev)
>>  	 */
>>  	tx_fifo_size = mram_config_vals[7];
>>  
>> +	pm_runtime_get_sync(&pdev->dev);
>> +
>>  	/* allocate the m_can device */
>>  	dev = alloc_m_can_dev(pdev, addr, tx_fifo_size);
>>  	if (!dev) {
>> @@ -1670,6 +1679,7 @@ static int m_can_plat_probe(struct platform_device *pdev)
>>  disable_hclk_ret:
>>  	clk_disable_unprepare(hclk);
>>  failed_ret:
>> +	pm_runtime_put_sync(&pdev->dev);
>>  	return ret;
>>  }
>>  
>> @@ -1726,6 +1736,9 @@ static int m_can_plat_remove(struct platform_device *pdev)
>>  	struct net_device *dev = platform_get_drvdata(pdev);
>>  
>>  	unregister_m_can_dev(dev);
>> +
>> +	pm_runtime_disable(&pdev->dev);
>> +
>>  	platform_set_drvdata(pdev, NULL);
>>  
>>  	free_m_can_dev(dev);
>>
>