linux-kernel - RE: [PATCH] usb: dwc3: gadget: fix miss isoc issue introduced by IRQ latency

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Message-ID: <878t0sl5br.fsf@linux.intel.com>
Date:   Fri, 14 Dec 2018 13:23:52 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     "Zengtao \(B\)" <prime.zeng@...ilicon.com>
Cc:     liangshengjun <liangshengjun@...ilicon.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb\@vger.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        Thinh Nguyen <thinhn@...opsys.com>
Subject: RE: [PATCH] usb: dwc3: gadget: fix miss isoc issue introduced by IRQ latency


Hi,

"Zengtao (B)" <prime.zeng@...ilicon.com> writes:
>>-----Original Message-----
>>From: Felipe Balbi [mailto:balbi@...nel.org]
>>Sent: Friday, December 14, 2018 4:52 PM
>>To: Zengtao (B) <prime.zeng@...ilicon.com>
>>Cc: liangshengjun <liangshengjun@...ilicon.com>; Zengtao (B)
>><prime.zeng@...ilicon.com>; Greg Kroah-Hartman
>><gregkh@...uxfoundation.org>; linux-usb@...r.kernel.org;
>>linux-kernel@...r.kernel.org
>>Subject: Re: [PATCH] usb: dwc3: gadget: fix miss isoc issue introduced by
>>IRQ latency
>>
>>* PGP Signed by an unknown key
>>
>>Zeng Tao <prime.zeng@...ilicon.com> writes:
>>
>>> If it's a busy system, some times when we start an isoc transfer, the
>>> framenumber get from the event buffer may be already elasped, in this
>>> case, we will get all the packets dropped due to miss isoc. And we
>>> turn into transfer nothing, to fix this issue, we need to fix the
>>> framenumber to make sure that it's not out of date.
>>>
>>> Signed-off-by: Liang Shengjun <liangshengjun@...ilicon.com>
>>> Signed-off-by: Zeng Tao <prime.zeng@...ilicon.com>
>>
>>There's a patch going upstream already doing this:
>>
>>https://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git/commit/?h
>>=next&id=d53701067f048b8b11635e964b6d3bd9a248c622
>>
>
> Sorry, I think I missed to update to the latest version. But I think my 
> patch is more efficient. Because I just sync the frame from the HW, it
>  won't fail and there is no need to extra tries.
>
> What do you think about it?

the 14 bits you use for your check is not representative of the actual
micro-frame you're currently in. Thinh explained that in the discussion
we had until we came to the patch I pointed you to above. Please look at
the mailing list archives for details.

-- 
balbi

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