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

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Message-ID: <b10b3df6-98de-01ce-33e5-dc050ab072cb@Microchip.com>
Date:   Fri, 22 Sep 2017 09:54:47 +0800
From:   "Yang, Wenyou" <Wenyou.Yang@...rochip.com>
To:     Franklin S Cooper Jr <fcooper@...com>,
        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

Hi Franklin,


On 2017/9/21 8:36, Franklin S Cooper Jr wrote:
> 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.
Please send a v3 patch.  I would like test it on my side.

>
>>> 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);
>>>
> --
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Best Regards,
Wenyou Yang