linux-kernel - Re: [PATCH v6 3/6] can: m

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Date:   Fri, 5 Jan 2018 09:23:32 +0800
From:   "Yang, Wenyou" <Wenyou.Yang@...rochip.com>
To:     Faiz Abbas <faiz_abbas@...com>,
        Marc Kleine-Budde <mkl@...gutronix.de>, <wg@...ndegger.com>,
        <robh+dt@...nel.org>, <mark.rutland@....com>
CC:     <linux-can@...r.kernel.org>, <netdev@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <nsekhar@...com>, <fcooper@...com>, <robh@...nel.org>,
        <sergei.shtylyov@...entembedded.com>
Subject: Re: [PATCH v6 3/6] can: m_can: Add PM Runtime



On 2018/1/4 23:17, Faiz Abbas wrote:
> Hi,
>
> On Wednesday 03 January 2018 08:47 PM, Marc Kleine-Budde wrote:
>> On 01/03/2018 04:06 PM, Faiz Abbas wrote:
>>> Hi,
>>>
>>> On Wednesday 03 January 2018 07:55 PM, Marc Kleine-Budde wrote:
>>>> On 01/03/2018 01:39 PM, Faiz Abbas wrote:
>>>>> On Tuesday 02 January 2018 09:37 PM, Marc Kleine-Budde wrote:
>>>>>> On 12/22/2017 02:31 PM, Faiz Abbas wrote:
>>>>>>> From: Franklin S Cooper Jr <fcooper@...com>
>>>>>>>
>>>>>>> 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.
>>>>>> There is no PM_RUNTIME anymore since 464ed18ebdb6 ("PM: Eliminate
>>>>>> CONFIG_PM_RUNTIME")
>>>>> Ok. Will change the commit message.
>>>>>
>>>>>> Have a look at the discussion: https://patchwork.kernel.org/patch/9436507/ :
>>>>>>
>>>>>>>> Well, I admit it would be nicer if drivers didn't have to worry about
>>>>>>>> whether or not CONFIG_PM was enabled.  A slightly cleaner approach
>>>>>>>> from the one outlined above would have the probe routine do this:
>>>>>>>>
>>>>>>>> 	my_power_up(dev);
>>>>>>>> 	pm_runtime_set_active(dev);
>>>>>>>> 	pm_runtime_get_noresume(dev);
>>>>>>>> 	pm_runtime_enable(dev);
>>>>> This discussion seems to be about cases in which CONFIG_PM is not
>>>>> enabled. CONFIG_PM is always selected in the case of omap devices.
>>>> Yes, but in the commit message you state that you need to support
>>>> systems that don't have PM_RUNTIME enabled. The only mainline SoCs I see
>>>> is "arch/arm/boot/dts/sama5d2.dtsi" so far. Please check if they select
>>>> CONFIG_PM, then we can make the driver much simpler.
>>> Actually the old clock management (for hclk which is the interface
>>> clock) is still required as mentioned in the cover letter. Will change
>>> the rather misleading description.
>> Ok. So you can use the code as discussed on
>> https://patchwork.kernel.org/patch/9436507/ ?
> Looking at the kernel configuration, it seems like SAMA5D2 platform
> selects CONFIG_PM (Wenyou, please confirm).
Confirmed.  The CONFIG_PM is selected.

> So, it seems like the only
> users of this driver always have CONFIG_PM enabled.
>
> So I guess the best way is to maintain the current code for pm_runtime_*
> and move the clock enable/disable to pm_runtime callbacks.
>
> Something like this:
>
> m_can_runtime_resume()
> {
> 	clk_prepare_enable(cclk);
> 	clk_prepare_enable(hclk);
> }
>
> m_can_runtime_suspend()
> {
> 	clk_disable_unprepare(cclk);
> 	clk_disable_unprepare(hclk);
> }
>
> SET_RUNTIME_PM_OPS(m_can_runtime_suspend, m_can_runtime_resume, NULL)
>
> static void m_can_start(struct net_device *dev)
> {
> 	pm_runtime_get_sync(dev)
> 	...
> }
>
> static void m_can_stop(struct net_device *dev)
> {
> 	...
> 	pm_runtime_put_sync(dev)
> }
>
> Does that sound okay? If yes, I will go work on the implementation.
>
> Thanks,
> Faiz
Best Regards,
Wenyou Yang