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Date:   Thu, 20 Oct 2022 15:53:10 -0500
From:   Jeff Vanhoof <jdv1029@gmail.com>
To:     Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Cc:     Jeffrey Vanhoof <jvanhoof@motorola.com>,
        "balbi@kernel.org" <balbi@kernel.org>,
        "corbet@lwn.net" <corbet@lwn.net>,
        "dan.scally@ideasonboard.com" <dan.scally@ideasonboard.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "laurent.pinchart@ideasonboard.com" 
        <laurent.pinchart@ideasonboard.com>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "m.grzeschik@pengutronix.de" <m.grzeschik@pengutronix.de>,
        "paul.elder@ideasonboard.com" <paul.elder@ideasonboard.com>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        Dan Vacura <W36195@motorola.com>
Subject: Re: [PATCH v3 2/6] usb: dwc3: gadget: cancel requests instead of
 release after missed isoc
Message-ID: <20221020205308.GA6319@qjv001-XeonWs>
References: <PUZPR03MB613101A170B0034F55401121A1289@PUZPR03MB6131.apcprd03.prod.outlook.com>
 <20221018223521.ytiwqsxmxoen5iyt@synopsys.com>
 <20221019014108.GA5732@qjv001-XeonWs>
 <20221019020240.exujmo7uvae4xfdi@synopsys.com>
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 <20221019190819.m35ai5fm3g5qpgqj@synopsys.com>
 <20221019213410.GA17789@qjv001-XeonWs>
 <20221019230555.gwovdtmnopwacirt@synopsys.com>
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Hi Thinh,

> On Wed, Oct 19, 2022 at 11:06:08PM +0000, Thinh Nguyen wrote:
> > Hi,
> >

<snip>

> > > 
> > > > The logic to detect underrun doesn't trigger because the queued list is
> > > > always non-empty, but the queued requests are expected to be missed
> > > > already. So you keep seeing missed isoc.
> > > > 
> > > > There are a few things you can mitigate this issue:
> > > > 1) Don't set IMI if the request indicates no_interrupt. This reduces the
> > > >    time software needs to handle interrupts.
> > > 
> > > 
> > > > 2) Improve the underrun detection logic.
> > > 
> > > 
> > > > 3) Increase the queuing frequency from the uvc to keep the request queue
> > > >    full. Note that reduce/avoid setting no_interrupt will allow the
> > > >    controller driver to update uvc often to keep requeuing new requests.
> > > > 
> > > > Best option is 3), but maybe we can do all 3.
> > > >
> > >

I forgot about your option 2. Will start looking into it.

Thanks,
Jeff