Re: [PATCH v6 3/6] can: m_can: Add PM Runtime

[Yang, Wenyou]

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@xxxxxx>
> > > > > > >
> > > > > > > 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