linux-kernel - Re: [PATCH v3] usb: ohci: add check for host controller functional states

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Date:   Mon, 11 Oct 2021 12:17:32 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     zhuyinbo <zhuyinbo@...ngson.cn>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <greg@...ah.com>,
        Patchwork Bot <patchwork-bot@...nel.org>
Subject: Re: [PATCH v3] usb: ohci: add check for host controller functional
 states

On Mon, Oct 11, 2021 at 01:10:18PM +0800, zhuyinbo wrote:
> 
> 在 2021/10/10 上午3:39, Alan Stern 写道:
> > On Sat, Oct 09, 2021 at 10:01:25AM +0800, zhuyinbo wrote:
> > > 在 2021/10/8 下午10:26, Alan Stern 写道:
> > > > On Fri, Oct 08, 2021 at 03:26:10PM +0800, Yinbo Zhu wrote:
> > > > > The usb states of ohci controller include UsbOperational, UsbReset,
> > > > > UsbSuspend and UsbResume. Among them, only the UsbOperational state
> > > > > supports launching the start of frame for host controller according
> > > > > the ohci protocol spec, but in S3/S4 press test procedure, it may
> > > > Nobody reading this will know what "S3/S4 press test procedure" means.
> > > > You have to explain it, or use a different name that people will
> > > > understand.
> > > okay, I got it.
> > > > > happen that the start of frame was launched in other usb states and
> > > > > cause ohci works abnormally then kernel will allways report rcu
> > > > > call trace. This patch was to add check for host controller
> > > > > functional states and if it is not UsbOperational state that need
> > > > > set INTR_SF in intrdisable register to ensure SOF Token generation
> > > > > was been disabled.
> > > > This doesn't make sense.  You already mentioned that only the
> > > > UsbOperational state supports sending start-of-frame packets.  So if the
> > > > controller is in a different state then it won't send these packets,
> > > > whether INTR_SF is enabled or not.
> > > > 
> > > > What problem are you really trying to solve?
> > > Only UsbOperational state supports sending start-of-frame packets, but in
> > > fact, in S3/S4 press test procedure,
> > > 
> > > usb in non-UsbOperational state that send start-of-frame packets but hc
> > > driver doesn't deal with this frame. and hc will
> > > 
> > > allways lauched the SOF for finishing the frame, the cpu will hand this sof
> > > interrupt and doesn't deal with time interrupt
> > > 
> > > that will cause rcu call trace then system doesn't suspend to memory/disk.
> > I still don't understand.
> > 
> > Are you saying that your OHCI controller behaves badly because it sends
> > SOF packets even when the state is different from UsbOperational?
> 
> HC will allways report the SoF interrupt in the all time when HC was not in
> NO-UsbOperation state.

How did your host controller get into the non-UsbOperational state?  
What part of the code is responsible for changing to a different state?

It looks like the only place where this could happen is in 
ohci_rh_suspend().  So if you disable SOF interrupts there, it should 
fix your problem.

> and no WritebackDoneHead interrupt that is the issue phenomenon. and this
> situation is badly state for ohci.
> 
> > 
> > > Hi Alan Stern,
> > > 
> > >      even though ed_rm_list is non-NULL, if hc in non-UsbOperation state set
> > > SoF status in usbsts register that is illegal,
> > > 
> > > at this time hcd doesn't need care URB whether finished,  because hc had
> > > into a wrong state. even thoug it doesn't has this patch,
> > > 
> > > URB was not be able to finish when hc in above worng state. except software
> > > can intervence this wrong state. but the SoF bit of usbsts
> > > 
> > > register was set by HC, and this action will happen always !!! software
> > > clear SoF state I think it isn't make sense. software only disable SoF
> > > 
> > > interrupt to fix HC wrong state.
> > This problem happens when you go into S3 or S4 suspend, right?  So you
> > should fix the problem by disabling INTR_SF when the root hub is
> > suspended.  Try adding
> > 
> > 	/* All ED unlinks should be finished, no need for SOF interrupts */
> > 	ohci_writel(ohci, OHCI_INTR_SF, &ohci->regs->intrdisable);
> > 
> > into ohci_rh_suspend(), just before the update_done_list() call.  If you
> > add this then INTR_SF will not be enabled during S3 or S4 suspend, so
> > the problem shouldn't occur.  Does that work for you?
> 
> The system doesn't suspend to disk completely by my test result and hc will
> always produce SoF interrupt.

Have you tried adding those two lines of code shown above?

If you haven't tested them, please don't write back until you have.

Alan Stern