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20 May 2020 06:47:36 -0700 IronPort-SDR: YVqKstJZAo/sdpxfBobGZ7tUK7GvIPb/f6rblNQ4LPlm9okxiPxYULhbLXjEVTksEqYmC26gIT baFrOHQQvwhw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,414,1583222400"; d="scan'208";a="466390121" Received: from mattu-haswell.fi.intel.com (HELO [10.237.72.170]) ([10.237.72.170]) by fmsmga005.fm.intel.com with ESMTP; 20 May 2020 06:47:32 -0700 Subject: Re: XHCI vs PCM2903B/PCM2904 part 2 To: Rik van Riel , linux-usb Cc: alsa-devel@alsa-project.org, "linux-kernel@vger.kernel.org" , Mathias Nyman , Greg Kroah-Hartman , Jaroslav Kysela , Takashi Iwai References: <273cc1c074cc4a4058f31afe487fb233f5cf0351.camel@surriel.com> From: Mathias Nyman Openpgp: preference=signencrypt Autocrypt: addr=mathias.nyman@linux.intel.com; prefer-encrypt=mutual; keydata= mQINBFMB0ccBEADd+nZnZrFDsIjQtclVz6OsqFOQ6k0nQdveiDNeBuwyFYykkBpaGekoHZ6f lH4ogPZzQ+pzoJEMlRGXc881BIggKMCMH86fYJGfZKWdfpg9O6mqSxyEuvBHKe9eZCBKPvoC L2iwygtO8TcXXSCynvXSeZrOwqAlwnxWNRm4J2ikDck5S5R+Qie0ZLJIfaId1hELofWfuhy+ tOK0plFR0HgVVp8O7zWYT2ewNcgAzQrRbzidA3LNRfkL7jrzyAxDapuejuK8TMrFQT/wW53e uegnXcRJaibJD84RUJt+mJrn5BvZ0MYfyDSc1yHVO+aZcpNr+71yZBQVgVEI/AuEQ0+p9wpt O9Wt4zO2KT/R5lq2lSz1MYMJrtfFRKkqC6PsDSB4lGSgl91XbibK5poxrIouVO2g9Jabg04T MIPpVUlPme3mkYHLZUsboemRQp5/pxV4HTFR0xNBCmsidBICHOYAepCzNmfLhfo1EW2Uf+t4 L8IowAaoURKdgcR2ydUXjhACVEA/Ldtp3ftF4hTQ46Qhba/p4MUFtDAQ5yeA5vQVuspiwsqB BoL/298+V119JzM998d70Z1clqTc8fiGMXyVnFv92QKShDKyXpiisQn2rrJVWeXEIVoldh6+ J8M3vTwzetnvIKpoQdSFJ2qxOdQ8iYRtz36WYl7hhT3/hwkHuQARAQABtCdNYXRoaWFzIE55 bWFuIDxtYXRoaWFzLm55bWFuQGdtYWlsLmNvbT6JAjsEEwECACUCGwMGCwkIBwMCBhUIAgkK CwQWAgMBAh4BAheABQJTAeo1AhkBAAoJEFiDn/uYk8VJOdIP/jhA+RpIZ7rdUHFIYkHEKzHw tkwrJczGA5TyLgQaI8YTCTPSvdNHU9Rj19mkjhUO/9MKvwfoT2RFYqhkrtk0K92STDaBNXTL JIi4IHBqjXOyJ/dPADU0xiRVtCHWkBgjEgR7Wihr7McSdVpgupsaXhbZjXXgtR/N7PE0Wltz hAL2GAnMuIeJyXhIdIMLb+uyoydPCzKdH6znfu6Ox76XfGWBCqLBbvqPXvk4oH03jcdt+8UG 2nfSeti/To9ANRZIlSKGjddCGMa3xzjtTx9ryf1Xr0MnY5PeyNLexpgHp93sc1BKxKKtYaT0 lR6p0QEKeaZ70623oB7Sa2Ts4IytqUVxkQKRkJVWeQiPJ/dZYTK5uo15GaVwufuF8VTwnMkC 4l5X+NUYNAH1U1bpRtlT40aoLEUhWKAyVdowxW4yGCP3nL5E69tZQQgsag+OnxBa6f88j63u wxmOJGNXcwCerkCb+wUPwJzChSifFYmuV5l89LKHgSbv0WHSN9OLkuhJO+I9fsCNvro1Y7dT U/yq4aSVzjaqPT3yrnQkzVDxrYT54FLWO1ssFKAOlcfeWzqrT9QNcHIzHMQYf5c03Kyq3yMI Xi91hkw2uc/GuA2CZ8dUD3BZhUT1dm0igE9NViE1M7F5lHQONEr7MOCg1hcrkngY62V6vh0f RcDeV0ISwlZWuQINBFMB0ccBEACXKmWvojkaG+kh/yipMmqZTrCozsLeGitxJzo5hq9ev31N 2XpPGx4AGhpccbco63SygpVN2bOd0W62fJJoxGohtf/g0uVtRSuK43OTstoBPqyY/35+VnAV oA5cnfvtdx5kQPIL6LRcxmYKgN4/3+A7ejIxbOrjWFmbWCC+SgX6mzHHBrV0OMki8R+NnrNa NkUmMmosi7jBSKdoi9VqDqgQTJF/GftvmaZHqgmVJDWNrCv7UiorhesfIWPt1O/AIk9luxlE dHwkx5zkWa9CGYvV6LfP9BznendEoO3qYZ9IcUlW727Le80Q1oh69QnHoI8pODDBBTJvEq1h bOWcPm/DsNmDD8Rwr/msRmRyIoxjasFi5WkM/K/pzujICKeUcNGNsDsEDJC5TCmRO/TlvCvm 0X+vdfEJRZV6Z+QFBflK1asUz9QHFre5csG8MyVZkwTR9yUiKi3KiqQdaEu+LuDD2CGF5t68 xEl66Y6mwfyiISkkm3ETA4E8rVZP1rZQBBm83c5kJEDvs0A4zrhKIPTcI1smK+TWbyVyrZ/a mGYDrZzpF2N8DfuNSqOQkLHIOL3vuOyx3HPzS05lY3p+IIVmnPOEdZhMsNDIGmVorFyRWa4K uYjBP/W3E5p9e6TvDSDzqhLoY1RHfAIadM3I8kEx5wqco67VIgbIHHB9DbRcxQARAQABiQIf BBgBAgAJBQJTAdHHAhsMAAoJEFiDn/uYk8VJb7AQAK56tgX8V1Wa6RmZDmZ8dmBC7W8nsMRz PcKWiDSMIvTJT5bygMy1lf7gbHXm7fqezRtSfXAXr/OJqSA8LB2LWfThLyuuCvrdNsQNrI+3 D+hjHJjhW/4185y3EdmwwHcelixPg0X9EF+lHCltV/w29Pv3PiGDkoKxJrnOpnU6jrwiBebz eAYBfpSEvrCm4CR4hf+T6MdCs64UzZnNt0nxL8mLCCAGmq1iks9M4bZk+LG36QjCKGh8PDXz 9OsnJmCggptClgjTa7pO6040OW76pcVrP2rZrkjo/Ld/gvSc7yMO/m9sIYxLIsR2NDxMNpmE q/H7WO+2bRG0vMmsndxpEYS4WnuhKutoTA/goBEhtHu1fg5KC+WYXp9wZyTfeNPrL0L8F3N1 BCEYefp2JSZ/a355X6r2ROGSRgIIeYjAiSMgGAZMPEVsdvKsYw6BH17hDRzltNyIj5S0dIhb Gjynb3sXforM/GVbr4mnuxTdLXQYlj2EJ4O4f0tkLlADT7podzKSlSuZsLi2D+ohKxtP3U/r 42i8PBnX2oAV0UIkYk7Oel/3hr0+BP666SnTls9RJuoXc7R5XQVsomqXID6GmjwFQR5Wh/RE IJtkiDAsk37cfZ9d1kZ2gCQryTV9lmflSOB6AFZkOLuEVSC5qW8M/s6IGDfYXN12YJaZPptJ fiD/ Message-ID: <296d1b03-fbc3-6107-950e-00d38633ea1f@linux.intel.com> Date: Wed, 20 May 2020 16:50:26 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <273cc1c074cc4a4058f31afe487fb233f5cf0351.camel@surriel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20.5.2020 14.26, Rik van Riel wrote: > After a few more weeks of digging, I have come to the tentative > conclusion that either the XHCI driver, or the USB sound driver, > or both, fail to handle USB errors correctly. > > I have some questions at the bottom, after a (brief-ish) explanation > of exactly what seems to go wrong. > > TL;DR: arecord from a misbehaving device can hang forever > after a USB error, due to poll on /dev/snd/timer never returning. > > The details: under some mysterious circumstances, the PCM290x > family sound chips can send more data than expected during an > isochronous transfer, leading to a babble error. Those > circumstances seem to in part depend on the USB host controller > and/or the electrical environment, since the chips work just > fine for most people. > > Receiving data past the end of the isochronous transfer window > scheduled for a device results in the XHCI controller throwing > a babble error, which moves the endpoint into halted state. > > This is followed by the host controller software sending a > reset endpoint command, and moving the endpoint into stopped > state, as specified on pages 164-165 of the XHCI specification. Note that isoch endpoints should generate buffer overrun instead of babble detect error on TD babble conditions. See xHCI spec 6.4.5 additional note 115. Or maybe a frame babble could halt an isoc endpoint, see xhci 4.10.2.4.1 but then you should see a port error and port going to disabled state. Any logs of this? mount -t debugfs none /sys/kernel/debug echo 'module xhci_hcd =p' >/sys/kernel/debug/dynamic_debug/control echo 'module usbcore =p' >/sys/kernel/debug/dynamic_debug/control echo 81920 > /sys/kernel/debug/tracing/buffer_size_kb echo 1 > /sys/kernel/debug/tracing/events/xhci-hcd/enable < trigger the issue > Send output of dmesg Send content of /sys/kernel/debug/tracing/trace > > However, the USB sound driver seems to have no idea that this > error happened. The function retire_capture_urb looks at the > status of each isochronous frame, but seems to be under the > assumption that the sound device just keeps on running. > > The function snd_complete_urb seems to only detect that the > device is not running if usb_submit_urb returns a failure. > > err = usb_submit_urb(urb, GFP_ATOMIC); > if (err == 0) > return; > > usb_audio_err(ep->chip, "cannot submit urb (err = %d)\n", err); > > if (ep->data_subs && ep->data_subs->pcm_substream) { > substream = ep->data_subs->pcm_substream; > snd_pcm_stop_xrun(substream); > } > > However, the XHCI driver will happily submit an URB to a > stopped device. Looking at the call trace usb_submit_urb -> > xhci_urb_enqueue -> xhci_queue_isoc_tx_prepare -> prepare_ring, > you can see this code: > > /* Make sure the endpoint has been added to xHC schedule */ > switch (ep_state) { > ... > case EP_STATE_HALTED: > xhci_dbg(xhci, "WARN halted endpoint, queueing URB anyway.\n"); > case EP_STATE_STOPPED: > case EP_STATE_RUNNING: > break; > > This leads me to a few questions: > - should retire_capture_urb call snd_pcm_stop_xrun, > or another function like it, if it sees certain > errors in the iso frame in the URB? > - should snd_complete_urb do something with these > errors, too, in case they happen on the sync frames > and not the data frames? > - does the XHCI code need to ring the doorbell when > submitting an URB to a stopped device, or is it > always up to the higher-level driver to fully reset > the device before it can do anything useful? xhci driver should ring the doorbell. xhci_queue_isoc_tx() giveback_first_trb() xhci_ring_ep_doorbell() when we are talking about babble or transaction errors the device might be completely unaware of the situation. Device side of the endpoint is not necessarily halted. xHC host will only halt its internal endpoint state, and it needs a reset endopoint command from the xhci driver to clear the internal halt state. -Mathias > - if a device in stopped state does not do anything > useful, should usb_submit_urb return an error? > - how should the USB sound driver recover from these > occasional and/or one-off errors? stop the sound > stream, or try to reinitialize the device and start > recording again? > > I am willing to write patches and can test with my > setup, but both the sound code and the USB code are > new to me so I would like to know what direction I > should go in :) >