linux-kernel - Re: [PATCH v3 2/7] clk: rockchip: rk3399: export 480M

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Date:	Tue, 16 Aug 2016 14:34:58 +0800
From:	Frank Wang <frank.wang@...k-chips.com>
To:	Heiko Stübner <heiko@...ech.de>
Cc:	Xing Zheng <zhengxing@...k-chips.com>,
	linux-rockchip@...ts.infradead.org, dianders@...omium.org,
	briannorris@...omium.org, huangtao@...k-chips.com,
	zhangqing@...k-chips.com, wulf@...k-chips.com,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>, linux-clk@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	daniel.meng@...k-chips.com, frank.wang@...k-chips.com
Subject: Re: [PATCH v3 2/7] clk: rockchip: rk3399: export 480M_SRC clock id
 for usbphy0/usbphy1

Hi Heiko,

On 2016/8/8 17:55, Frank Wang wrote:
> Hi Heiko,
>
> On 2016/8/6 0:05, Heiko Stübner wrote:
>> Hi Frank,
>>
>> Am Freitag, 5. August 2016, 16:34:42 schrieb Frank Wang:
>>> On 2016/8/5 3:10, Heiko Stübner wrote:
>>>> Am Dienstag, 2. August 2016, 15:19:56 schrieb Xing Zheng:
>>>>> Export these source clocks for usbphy.
>>>>>
>>>>> Signed-off-by: Xing Zheng <zhengxing@...k-chips.com>
>>>> can you please provide a rationale why you need manual control over 
>>>> that
>>>> intermediate clock?
>>> Well, From below graph, you can see that 'clk_usbphyX_480m' is 
>>> generated
>>> from usb2phy, and 'clk_usbphy_480m' which select from
>>> clk_usbphyX_480m_src via a gate (G13[12])  provided 480M clock to other
>>> modules.
>>>
>>>     xin24m
>>>       |__ clk_usb2phy0_ref
>>>       |     |
>>>       |     |__ clk_usbphy0_480m
>>>       |           |
>>>       |           |__clk_usbphy0_480m_src
>>>       |                |
>>>       |                |__clk_usbphy_480m
>>>       |                     |__ ... ...
>>>       |
>>>       |__ clk_usb2phy1_ref
>>>             |
>>>             |__ clk_usbphy1_480m
>>>                   |
>>>                   |__clk_usbphy1_480m_src
>>>> The two usbphys seem to use the clk_usb2phyX_ref clocks, generate the
>>>> 480m
>>>> clocks, but do not seem to need the clk_usbphyX_480m_src gates.
>>> Yeah, they used to be. However, the story went something like this,
>>>
>>> Some PM suspend process related ehci/ohci controller are base on 480m
>>> clocks, unfortunately, usb2-phy suspended earlier than ehci/ohci
>>> (usb2-phy will be auto suspended if no devices plug-in), and the
>>> clk-480m provided by it was disabled if no module used. As a result, 
>>> the
>>> PM suspend process was blocked when it run into ehci/ohci module.
>> ah, so the ehci controller needs that 480m clock as well? Do you 
>> happen to
>> have example patches for the ehci/ohci side already? I'd like to peak 
>> at what
>> you mean with "some PM suspend process related" things.
>
> Actually, no patches for it, I just make below steps manually :-).
> 1. set two usb2-phy into suspend mode.
> 2. disable 480m clock on each usb2-phy (assume only usb2-phy used it).
> 3. press power button let system into PM suspend.
>
> Then, the kernel will be blocked and you can see the following log 
> from console.
> ... ....
> [  123.763848] calling  usb6+ @ 166, parent: xhci-hcd.0.auto
> [  123.764503] call usb6+ returned 0 after 163 usecs
> [  123.765106] calling  usb5+ @ 166, parent: xhci-hcd.0.auto
> [  123.765719] call usb5+ returned 0 after 121 usecs
> [  123.766294] calling  usb4+ @ 166, parent: fe3e0000.usb
> [  123.766917] calling  usb3+ @ 55, parent: fe3a0000.usb
>

May I know have you tried reproducing on your board or not?

>>
>> Depending on what is actually needed, you could also pull the usbphy 
>> out of
>> autosuspend in a pm-prepare callback of the phy driver itself ... see
>> http://lxr.free-electrons.com/source/include/linux/pm.h#L86
>>
>> Like
>> - in the .prepare callback make sure to unsuspend the phy
>>    and deactivate the autosuspend
>> - ehci/ohci will poweroff the phy in it s suspend callback (already 
>> does that)
>
> Hmm, do you remember that we have previously discussed there are some 
> oddities in ehci/ohci driver? phy_power_on() gets called twice at 
> ehci/ohci driver probe time, one is at pdata->power_on(); another is 
> at usb_add_hcd(), then the power_count of phy increases to 2,  but 
> phy_power_off() is just invoked one time when ehci/ohci goes to PM 
> suspend, so phy->ops->power_off is never be invoked.
>
> In this way,  the usb-phy maybe never go to suspend.
>
>> - suspend -> resume
>> - ehci/ohci will poweron the phy
>> - in the phy's .complete callback you can reactivate the autosuspend 
>> timer
>>
>> Because it looks more like you actually need the phy and not the 
>> clock alone.
>> So it would be nicer to use mechanisms already in place instead of 
>> creating
>> new dependencies.
>>
>
> Theoretically, phy_init() will be invoked when ehci/ohci power on, and 
> the sm_work will be reactivated (have already implemented) in 
> phy->ops->init, but unfortunately, the same issue as phy_power_on() 
> mentioned above, it never run there too .
>

Would you like to give some comments on above two oddities please?

BR.
Frank

>>> Hence, we are planing to refer clk_usbphyX_480m_src into each ehci/ohci
>>> driver. Maybe you will challenge why not refer clk_usbphy_480m 
>>> directly?
>>> because there are two ehci/ohci connected in the different usb2phy, and
>>> only one clk_usbphy_480m clock was selected in clock tree.
>> Nope, no argument from me as I fully understand that each phy 
>> provides its own
>> 480m clock :-) .
>>
>>
>> Heiko
>>
>>