From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: patch "tty: serial: OMAP: ensure FIFO levels are set correctly in non-DMA" added to tty tree Date: Fri, 3 Feb 2012 23:11:13 +1100 Message-ID: <20120203231113.25ae2d3a@notabene.brown> References: <13274430881471@kroah.org> <20120126042155.GA3185@suse.de> <20120126191604.GA15516@suse.de> <20120203150708.386951d2@notabene.brown> <20120203205401.5ddf241d@notabene.brown> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_//lAh3i/SDYh.FNuHS__a+X7"; protocol="application/pgp-signature" Return-path: In-Reply-To: Sender: linux-omap-owner@vger.kernel.org To: Grazvydas Ignotas Cc: Paul Walmsley , Greg KH , greg@kroah.com, khilman@ti.com, govindraj.raja@ti.com, tomi.valkeinen@ti.com, linux-serial@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-serial@vger.kernel.org --Sig_//lAh3i/SDYh.FNuHS__a+X7 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Fri, 3 Feb 2012 13:42:13 +0200 Grazvydas Ignotas wro= te: > On Fri, Feb 3, 2012 at 11:54 AM, NeilBrown wrote: > > On Thu, 2 Feb 2012 22:45:53 -0700 (MST) Paul Walmsley = wrote: > >> On Fri, 3 Feb 2012, NeilBrown wrote: > >> > >> > then CPUIDLE enters lower states and I think it uses less power but I > >> > sometimes lose the first char I type (that is known) but also I some= times get > >> > corruption on output. > >> > >> I don't see any output corruption on 35xx BeagleBoard, either with or > >> without these patches. =C2=A0So this is presumably a 37xx-centric prob= lem, and > >> unrelated to these patches, I would guess. > > > > Maybe it is 37xx specific. =C2=A0I think this is a DM3730. >=20 > Not sure if it's the same problem but with 3530 on 3.2 with > sleep_timeout set, I usually get first char dropped (as expected) but > sometimes I get corrupted char instead too. Corrupt char seems to > almost always happen if I set cpufreq to powersave, on performace it's > almost always ok, so maybe it's some timing problem, I see that too - I'm glad someone else does :-) If I look at the corruption as compared to the expected character, it is always the case some it has been shifted down a few bits, with '1's shifted in the top. As bytes are sent lsb first followed by stop bits which are '1', this is completely consistent with clocking the bits in a little bit late. I see this with baud rates of 115200 and higher, but never with lower. My theory is that there is a delay between the falling RX line waking the system up, and the CPU enabling the UART - whether enabling the clocks or doing a full config, I am not sure - though I think the former. Maybe if we could enable the UART clocks immediately after returning from t= he WFI instruction we could avoid the corruption.... NeilBrown --Sig_//lAh3i/SDYh.FNuHS__a+X7 Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBTyvO4Tnsnt1WYoG5AQLebhAAj2LIQ6GoEPQ98hvEEB8Ar5o9jQj8u6EJ YpgEBM2RZpx2/XBnaIs2oRSNC0h3tLgErJo9sNISCJTez9ZTmFV1z0Q9sA1dOFRU JkvAN34fobqcyfrhM9ftFxAHtkg+uHeO4oreCT45VePPvM3MGZsosEkNHGe8lJL7 nwGYB9aOTLglkID1FJz7kWNS/YodzSXF37FxXWhQew6Dnl/UeXITZZS1MvTvwthv kYG/3akp2+whRYcQfVnCnfUCdFZ87cbgUntMo5W4jRa+sTtCRlP2pw2C+RkJYXQx Aym4kupe+ggWcYgXI4bbMQK1ey8WXzYCSJXO5aUo0dmRC8vEqQV6EU4QLPcvpUJ0 TlFhDiMS7Xu8Nn8mRKHQU09Xdx9pAqZiHwNHUM1s4SG1lEdYmI7npl/n4CCOj1EC VJAP4QVwnB1Ew48mvjmIPrrc9QTXYmDhU1NxK0QZ/P4qw0hYrnCvFylNP8Hd9a6k mIxmTW8sYGkodlafujAEgt3JqJ3LMOLaStnPAS4nnaPVdELtIQ6VbYF4V6PagP8k D0SB9Tfnn1jv0qwlqKz48rleRgcKa4NxPPSMqZcpfOJcs3HCTZKFWo9aeqb09u/7 dMBDXSZ9LHeOHfQmIPMHSFVi3ZrBeo7CRe8pJ8X4EsuvcKxm7kQKJiuck3AmsQsg 0miw117LdAg= =DTxT -----END PGP SIGNATURE----- --Sig_//lAh3i/SDYh.FNuHS__a+X7--