From: Felipe Balbi <balbi@kernel.org>
To: Dejin Zheng <zhengdejin5@gmail.com>
Cc: gregkh@linuxfoundation.org, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org,
Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Subject: Re: [PATCH v3] usb: dwc3: core: fix a issue about clear connect state
Date: Wed, 28 Oct 2020 15:57:03 +0200 [thread overview]
Message-ID: <87y2jqlahc.fsf@kernel.org> (raw)
In-Reply-To: <20201028125812.GA59692@nuc8i5>
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Hi,
Dejin Zheng <zhengdejin5@gmail.com> writes:
>> Dejin Zheng <zhengdejin5@gmail.com> writes:
>> > According to Synopsys Programming Guide chapter 2.2 Register Resets,
>> > it cannot reset the DCTL register by setting DCTL.CSFTRST for core soft
>> > reset, if DWC3 controller as a slave device and stay connected with a usb
>> > host, then, while rebooting linux, it will fail to reinitialize dwc3 as a
>> > slave device when the DWC3 controller did not power off. because the
>> > connection status is incorrect, so we also need to clear DCTL.RUN_STOP
>> > bit for disabling connect when doing core soft reset. There will still
>> > be other stale configuration in DCTL, so reset the other fields of DCTL
>> > to the default value 0.
>>
>> This commit log is a bit hard to understand. When does this problem
>> actually happen? It seems like it's in the case of, perhaps, kexecing
>> into a new kernel, is that right?
>>
> It happens when entering the kernel for the second time after the reboot
> command.
>
>> At the time dwc3_core_soft_reset() is called, the assumption is that
>> we're starting with a clean core, from power up. If we have stale
>> configuration from a previous run, we should fix this on the exit
>> path. Note that if we're reaching probe with pull up connected, we
>> already have issues elsewhere.
>>
>> I think this is not the right fix for the problem.
>>
> I think you are right, Thinh also suggested me fix it on the exit path
> in the previous patch v2. Do you think I can do these cleanups in the
> shutdown hook of this driver? Balbi, is there a more suitable place to
> do this by your rich experience? Thanks!
I don't think shutdown is called during removal, I'm not sure. I think
we had some fixes done in shutdown time, though. Test it out, but make
sure there are no issues with a regular modprobe cycle.
--
balbi
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next prev parent reply other threads:[~2020-10-29 0:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-20 13:58 [PATCH v3] usb: dwc3: core: fix a issue about clear connect state Dejin Zheng
2020-10-27 8:33 ` Felipe Balbi
2020-10-28 13:46 ` Dejin Zheng
2020-10-28 13:57 ` Felipe Balbi [this message]
2020-10-28 14:43 ` Dejin Zheng
2020-10-30 15:15 ` Dejin Zheng
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