Re: [PATCH 3/3] arm64: dts: rockchip: add clk-480m for ehci and ohci of rk3399

[Xing Zheng]

// Frank

Hi Doug,  Brain,
    Thanks for the reply.
    Sorry I forgot these patches have been sent earlier, and Frank have 
some explained and discussed with Heiko.
Please see https://patchwork.kernel.org/patch/9255245/
    Perhaps we can move to that patch tree to continue the discussion.

    I think Frank and William will help us to continue checking these.

Thanks

å 2016å12æ15æ 08:10, Doug Anderson åé:
> Hi,
>
> On Wed, Dec 14, 2016 at 2:11 AM, Xing Zheng <zhengxing@xxxxxxxxxxxxxx> wrote:
> > From: William wu <wulf@xxxxxxxxxxxxxx>
> >
> > We found that the suspend process was blocked when it run into
> > ehci/ohci module due to clk-480m of usb2-phy was disabled.
> >
> > The root cause is that usb2-phy suspended earlier than ehci/ohci
> > (usb2-phy will be auto suspended if no devices plug-in).
> This is really weird, but I can confirm it is true on my system too
> (kernel-4.4 based).  At least I see:
>
> [  208.012065] calling  usb1+ @ 4984, parent: fe380000.usb, cb: usb_dev_suspend
> [  208.569112] calling  ff770000.syscon:usb2-phy@e450+ @ 4983, parent:
> ff770000.syscon, cb: platform_pm_suspend
> [  208.569113] call ff770000.syscon:usb2-phy@e450+ returned 0 after 0 usecs
> [  208.569439] calling  fe380000.usb+ @ 4983, parent: platform, cb:
> platform_pm_suspend
> [  208.569444] call fe380000.usb+ returned 0 after 4 usecs
>
>
> In general I thought that suspend order was supposed to be related to
> probe order.  So if your probe order is A, B, C then your suspend
> order would be C, B, A.  ...and we know for sure that the USB PHY
> needs to probe _before_ the main USB controller.  If it didn't then
> you'd get an EPROBE_DEFER in the USB controller, right?  So that means
> that the USB controller should be suspending before its PHY.
>
> Any chance this is somehow related to async probe?  I'm not a huge
> expert on async probe but I guess I could imagine things getting
> confused if you had a sequence like this:
>
> 1. Start USB probe (async)
> 2. Start PHY probe
> 3. Finish PHY probe
> 4. In USB probe, ask for PHY--no problems since PHY probe finished
> 5. Finish USB probe
>
> The probe order would be USB before PHY even though the USB probe
> _depended_ on the PHY probe being finished...  :-/  Anyway, probably
> I'm just misunderstanding something and someone can tell me how dumb I
> am...
>
> I also notice that the ehci_platform_power_off() function we're
> actually making PHY commands right before the same commands that turn
> off our clocks.  Presumably those commands aren't really so good to do
> if the PHY has already been suspended?
>
> Actually, does the PHY suspend from platform_pm_suspend() actually
> even do anything?  It doesn't look like it.  It looks as if all the
> PHY cares about is init/exit and on/off...  ...and it looks as if the
> PHY should be turned off by the EHCI controller at about the same time
> it turns off its clocks...
>
> I haven't fully dug, but is there any chance that things are getting
> confused between the OTG PHY and the Host PHY?  Maybe when we turn off
> the OTG PHY it turns off something that the host PHY needs?
>
>
> > and the
> > clk-480m provided by it was disabled if no module used. However,
> > some suspend process related ehci/ohci are base on this clock,
> > so we should refer it into ehci/ohci driver to prevent this case.
> Though I don't actually have details about the internals of the chip,
> it does seem highly likely that the USB block actually uses this clock
> for some things, so it doesn't seem insane (to me) to have the USB
> controller request that the clock be on.  So, in general, I don't have
> lots of objections to including the USB PHY Clock here.
>
> ...but I think you have the wrong clock (please correct me if I'm
> wrong).  I think you really wanted your input clock to be
> "clk_usbphy0_480m", not "clk_usbphy0_480m_src".  Specifically I
> believe there is a gate between the clock outputted by the PHY and the
> USB Controller itself.  I'm guessing that the gate is only there
> between the PHY and the "clk_usbphy_480m" MUX.
>
> As evidence, I have a totally functioning system right now where
> "clk_usbphy0_480m_src" is currently gated.
>
> That means really you should be changing your clocks to this (untested):
>
>                 clocks = <&cru HCLK_HOST0>, <&cru HCLK_HOST0_ARB>,
>                          <&u2phy0>;
>
> ...and then you could drop the other two patches in this series.
>
> ===
>
> OK, I actually briefly tested my proposed change and it at least seems
> to build and boot OK.  You'd have to test it to make sure it makes
> your tests pass...
>
> ===
>
> So I guess to summarize all the above:
>
> * It seems to me like there's some deeper root cause and your patch
> will at most put a band-aid on it.  Seems like digging out the root
> cause is a good idea.
>
> * Though I don't believe it solves the root problem, the idea of the
> USB Controller holding onto the PHY clock doesn't seem wrong.
>
> * You're holding onto the wrong clock in your patch--you want the one
> before the gate (I think).
>
>
> -Doug


--
- Xing Zheng