Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758606AbcCVJup (ORCPT ); Tue, 22 Mar 2016 05:50:45 -0400 Received: from chaos.universe-factory.net ([37.72.148.22]:32898 "EHLO chaos.universe-factory.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758588AbcCVJug (ORCPT ); Tue, 22 Mar 2016 05:50:36 -0400 Subject: Re: Nonterministic hang during bootconsole/console handover on ath79 To: Antony Pavlov References: <56F07DA1.8080404@universe-factory.net> <20160322084046.7196890a7c157503cd0ea0d5@gmail.com> Cc: Ralf Baechle , gregkh@linuxfoundation.org, jslaby@suse.com, linux-mips@linux-mips.org, linux-serial@vger.kernel.org, "linux-kernel@vger.kernel.org" , Peter Mamonov From: Matthias Schiffer Message-ID: <56F1155C.7080506@universe-factory.net> Date: Tue, 22 Mar 2016 10:50:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 MIME-Version: 1.0 In-Reply-To: <20160322084046.7196890a7c157503cd0ea0d5@gmail.com> Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="PeX5h5CuJHvVMVEJJIDOSGthFIQ8VUUW1" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3623 Lines: 97 This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --PeX5h5CuJHvVMVEJJIDOSGthFIQ8VUUW1 Content-Type: multipart/mixed; boundary="9d17nTEchecUAE9Pmh2cPXG2R6TpWmOP8" From: Matthias Schiffer To: Antony Pavlov Cc: Ralf Baechle , gregkh@linuxfoundation.org, jslaby@suse.com, linux-mips@linux-mips.org, linux-serial@vger.kernel.org, "linux-kernel@vger.kernel.org" , Peter Mamonov Message-ID: <56F1155C.7080506@universe-factory.net> Subject: Re: Nonterministic hang during bootconsole/console handover on ath79 References: <56F07DA1.8080404@universe-factory.net> <20160322084046.7196890a7c157503cd0ea0d5@gmail.com> In-Reply-To: <20160322084046.7196890a7c157503cd0ea0d5@gmail.com> --9d17nTEchecUAE9Pmh2cPXG2R6TpWmOP8 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 03/22/2016 06:40 AM, Antony Pavlov wrote: > On Tue, 22 Mar 2016 00:02:57 +0100 > Matthias Schiffer wrote: >=20 >> Hi, >> we're experiencing weird nondeterministic hangs during bootconsole/con= sole >> handover on some ath79 systems on OpenWrt. I've seen this issue myself= on >> kernel 3.18.23~3.18.27 on a AR7241-based system, but according to othe= r >> reports ([1], [2]) kernel 4.1.x is affected as well, and other SoCs li= ke >> QCA953x likewise. >> >> See the log below for the exact place it hangs; the log was taken in d= uring >> a good boot; a bad boot will just hang forever at the marked location.= The >> issue is extremely hard to debug, as changing the timing in any way (l= ike >> adding additional printk) will usually make it work without problems. = (Even >> recompiling the kernel with the same config, but different uname times= tamp >> will make the occurence more or less likely) >> >> My theory is the following: >> >> As soon as ttyS0 is detected and installed as the console, there are t= wo >> console drivers active on the serial port at the same time: early0 and= >> ttyS0. I suspect that the hang occurs when the primitive early0 >> implementation prom_putchar_ar71xx waits indefinitely on THRE, >=20 > Can you use EJTAG to prove your theory? >=20 > --=20 > Best regards, > Antony Pavlov >=20 Unfortunately, the board I can reproduce this at the moment does not have= an accessible JTAG port. I hope I can reproduce it on other hardware whic= h is more developer-friendly, but no luck so far. Matthias --9d17nTEchecUAE9Pmh2cPXG2R6TpWmOP8-- --PeX5h5CuJHvVMVEJJIDOSGthFIQ8VUUW1 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCgAGBQJW8RVcAAoJEBbvP2TLIB2cgEQQAIQfVgeXprFvdsAq/8gUa1Ra oQUXPOp6KSMiBIEOqyOYH648TZcrdH7id8oZh16/x/uCLQG/TnwHe6Ks4udseUiJ 3M319vuuSJwZ0/fR2TpVd3jMP2vhFzmxhOZEBYgJr2KPb/OMTtiVqcOEJmqOzRC3 LbxxRgo8UvakTG3v3/brQJ1VCHNnvpu5jyKVSY7w8TsGFEkRY71aw9tv//0NQ3/T t4nxJ/FTm9Ku6zRCDT7uzB/Gd43fQVMKzfRaIUqoGPxzxeL1JW54itLBaVtqimhS 3bxP/zOF787xHpa0nH57j6EYZM4jSqyT3zW+JaqEMz/SQi9f/SP2ZJavhAruOWtb F5bY5Nmuk+gJi5slEe1IqEnP7uOhj3WH0ygf5qkxGq7tKDQ8p2LqNoBOAzbvd+xV drC/o/4pUCK0wpyQqZsTbmtJjG6w9PR1NkcPf43maegQHUtA/DW9Ny7DTJhNzBLG OGtjo6Sa0E7q6dCBC0QdUnwS+azPQfCtKZFpUIIjKTH/IxMPLp9bw/DRJ8l8dbvl r/CK6CNsF/pw74QXK4aY081VjVvsMytjK2XjbPj2opUlxNqp/VTLlsxxZhTQZEc5 14to3GpceXGEeC74+Af6KFA9ys8Km3EE916ZLpkwX4MmKADIxgfxRIbF208YWHUb XyMeYFOUne+Q+DT/OEGV =+Ilz -----END PGP SIGNATURE----- --PeX5h5CuJHvVMVEJJIDOSGthFIQ8VUUW1--