linux-kernel - Re: [PATCH] soc: rockchip: power-domain: remove PM clocks

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Date:   Thu, 01 Mar 2018 11:40:40 +0800
From:   JeffyChen <jeffy.chen@...k-chips.com>
To:     Tomasz Figa <tfiga@...omium.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Robin Murphy <robin.murphy@....com>,
        Heiko Stuebner <heiko@...ech.de>,
        Caesar Wang <wxt@...k-chips.com>,
        Elaine Zhang <zhangqing@...k-chips.com>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH] soc: rockchip: power-domain: remove PM clocks

Hi guys,

if i'm reading the code right, the PM clk means:
1/ the clocks which would be enabled while power on
2/ these clocks are optional, it's ok if anything wrong with them
3/ controlled by pm_domain(or USE_PM_CLK_RUNTIME_OPS & pm_clk_add_notifier)

and currently we're adding all clocks of the attached device as PM clk 
in rockchip PM domain driver, which seems wrong. because we might have 
these kinds of clocks:
1/ critical, should block power on if anything wrong with it(failed to 
get/ prepare/ enable)
2/ optional, could ignore it if anything wrong
3/ only required in some special cases, for example register r/w, and 
doesn't need to stay enabled while power on

so maybe we can:
1/ let the device(dts) or driver decide which clock is PM clk, and add 
it using *pm_clk_add* APIs (even of_pm_clk_add_clks() if all clocks are 
pm clk)

2/ add support for critical PM clk, which would return error to the 
driver if anything wrong

3/ make sure PM clk always be controlled(otherwise it might be 
unexpected disabled by other clocks under the same clk parent?):
  a) make sure Runtime PM is always enabled. and as discussed, we can 
select PM in ARCH_ROCKCHIP

  b) make sure the device has a PM domain to control PM clk:
select ROCKCHIP_PM_DOMAINS for ARCH_ROCKCHIP(that would also select 
PM_GENERIC_DOMAINS)

check dev->pm_domain before hand over PM clk, since we only care about 
EPROBE_DEFER when attach PM domain:
         ret = dev_pm_domain_attach(_dev, true);
         if (ret != -EPROBE_DEFER) {
                 if (drv->probe) {
                         ret = drv->probe(dev);

or

  c) make pm_clk_suspend/pm_clk_resume part of the generic PM Runtime 
flow(even without a PM domain)


On 02/28/2018 10:07 PM, Tomasz Figa wrote:
> On Wed, Feb 28, 2018 at 10:11 PM, Geert Uytterhoeven
> <geert@...ux-m68k.org> wrote:
>> Hi Tomasz,
>>
>> On Wed, Feb 28, 2018 at 1:49 PM, Tomasz Figa <tfiga@...omium.org> wrote:
>>> On Wed, Feb 28, 2018 at 9:32 PM, Geert Uytterhoeven
>>> <geert@...ux-m68k.org> wrote:
>>>> On Wed, Feb 28, 2018 at 1:29 PM, Tomasz Figa <tfiga@...omium.org> wrote:
>>>>> Also, how about systems where runtime PM is disabled? I think that's
>>>>> one of the reasons we control the clocks explicitly in the drivers
>>>>> anyway.
>>>>
>>>> On many platforms, Runtime PM is always enabled.
>>>
>>> Can we make such assumption? If so, could we just make an explicit
>>> "select PM_RUNTIME" in Kconfig of the SoC?
>>
>> Note that the PM_RUNTIME symbol was removed in commit 464ed18ebdb6236f
>> ("PM: Eliminate CONFIG_PM_RUNTIME"), in favor of plain PM.
>>
>> The following already select PM unconditionally:
>>    - ARCH_OMAP2PLUS_TYPICAL
>>    - ARCH_RENESAS (except EMEV2)
>>    - ARCH_TEGRA
>>    - ARCH_VEXPRESS
>
> Thanks! Sounds like we might be able to simplify a lot of things with
> doing the same for Rockchip.
>
> Best regards,
> Tomasz
>
>
>