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Subject: Re: [PATCH v3] usb: ohci: add check for host controller functional
 states
From:   zhuyinbo <zhuyinbo@loongson.cn>
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        Greg Kroah-Hartman <greg@kroah.com>,
        Patchwork Bot <patchwork-bot@kernel.org>
References: <1633677970-10619-1-git-send-email-zhuyinbo@loongson.cn>
 <20211008142639.GA721194@rowland.harvard.edu>
 <7a505fc4-ec47-ac83-633f-7a5251bd5f82@loongson.cn>
 <20211009193901.GA753830@rowland.harvard.edu>
 <adc67ae2-e162-a427-a8a9-7df55c92a00c@loongson.cn>
Message-ID: <8ef37927-c815-99ac-28b5-940d66c904d0@loongson.cn>
Date:   Mon, 11 Oct 2021 15:22:00 +0800
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在 2021/10/11 下午1:10, zhuyinbo 写道:
>
> 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.
>
> 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.
>
> I encountered SoF interrupt  issue when HC in UsbSuspend state. and I 
> think when hc in
>
> UsbResume/UsbRest/ SoF interrupt issue may be happen so I disable 
> INTR_SF in ohci_irq.
>
> So I think disable INTR_SF in suspend function which this way isn't 
> good for me.
>
>     In addition, I hope my patch was not only fix the bug i 
> encountered and it can limit HC into badly state and it should be the
>
> base limit condition and prevent more unknown problems.  In fact, HC 
> doesn't deal with ed/td list and done list by the ohci spec, so
>
> I think my patch has no risk for ohci.
>
>       by the way, root hub state isn't completely same with HC, but 
> the root hub reset and resume signaling are controlled by the hcfs bits.
>
> and hcd can set hcfs to decide hc usb state, so I judge whether set 
> SF_INT to interrupt disable register only depend on HC state.

And I have a test, ohci_rh_suspend was called that HC state as gerneral 
was also UsbOperational state whatever do s3/s4 test or power on to boot 
kernel.

but HCD record it as suspend state on root hub at this time.

>
>>
>>>        In additon, when kernel include my patch, that it does't 
>>> happen about
>>> what you descriped that driver will not be able to finish unlinging 
>>> URBs.
>>>
>>> Because above issue happen in S3/S4(Suspend to disk/Suspend to mem) 
>>> test
>>> procedure, if ed_rm_lis is no-NULL but my patch disable SoF interrupt.
>>>
>>> then when S3/S4 recovery to cpu idle state that usb resume will be 
>>> called,
>>> reume function has following logic, URB will continue to be processed.
>>>
>>>        static int ohci_rh_resume (struct ohci_hcd *ohci)
>>>
>>>       {
>>>
>>>          ...
>>>
>>>          242         if (ohci->ed_rm_list)
>>>          243                 ohci_writel (ohci, OHCI_INTR_SF,
>>> &ohci->regs->intrenable);
>>>
>>>         ...
>>>
>>>        }
>> I'm worried that your patch may disable INTR_SF even when the controller
>> has not gone into S3 or S4 suspend.  Maybe this won't cause problems,
>> but it's better to be safe and do the disable _only_ when a suspend
>> occurs.
>>
>> Alan Stern
>
> Hi  Alan Stern,
>
>     According to the previous statement, I think my patch has no risk 
> on ohci.
>
>
>
>