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

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Date:   Thu, 4 Jan 2018 16:18:02 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Faiz Abbas <faiz_abbas@...com>, 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,
        Wenyou.Yang@...rochip.com, sergei.shtylyov@...entembedded.com
Subject: Re: [PATCH v6 3/6] can: m_can: Add PM Runtime

On 01/04/2018 04:17 PM, 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). 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.

ACK + error checking.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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