From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA382C433F5 for ; Wed, 5 Jan 2022 10:57:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239561AbiAEK5N (ORCPT ); Wed, 5 Jan 2022 05:57:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50200 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239570AbiAEK5M (ORCPT ); Wed, 5 Jan 2022 05:57:12 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8FB60C061761 for ; Wed, 5 Jan 2022 02:57:12 -0800 (PST) Received: from gallifrey.ext.pengutronix.de ([2001:67c:670:201:5054:ff:fe8d:eefb] helo=bjornoya.blackshift.org) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1n53yb-00088L-4z; Wed, 05 Jan 2022 11:57:05 +0100 Received: from pengutronix.de (2a03-f580-87bc-d400-7899-4998-133d-b4b9.ip6.dokom21.de [IPv6:2a03:f580:87bc:d400:7899:4998:133d:b4b9]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) (Authenticated sender: mkl-all@blackshift.org) by smtp.blackshift.org (Postfix) with ESMTPSA id 5AF1C6D18A3; Wed, 5 Jan 2022 10:57:03 +0000 (UTC) Date: Wed, 5 Jan 2022 11:57:02 +0100 From: Marc Kleine-Budde To: Greg Kroah-Hartman Cc: Tomasz =?utf-8?Q?Mo=C5=84?= , Pengutronix Kernel Team , Jiri Slaby , Sascha Hauer , NXP Linux Team , linux-serial@vger.kernel.org, Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= , Shawn Guo , Fabio Estevam , k.drobinski@camlintechnologies.com Subject: Re: [PATCH] serial: imx: reduce RX interrupt frequency Message-ID: <20220105105702.vrz7u3nam27izwah@pengutronix.de> References: <20220104103203.2033673-1-tomasz.mon@camlingroup.com> <7e509806-77ae-8f94-2563-7dbae1ebca17@camlingroup.com> <20220104224900.u3omfbilejx2jawr@pengutronix.de> <4c48200b-cc2e-0766-a002-831a789d4879@camlingroup.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="5wlq3p55oytqdc3h" Content-Disposition: inline In-Reply-To: X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-serial@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org --5wlq3p55oytqdc3h Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 05.01.2022 11:37:05, Greg Kroah-Hartman wrote: > On Wed, Jan 05, 2022 at 08:59:09AM +0100, Tomasz Mo=C5=84 wrote: > > On 04.01.2022 23:49, Uwe Kleine-K=C3=B6nig wrote: > > > On Tue, Jan 04, 2022 at 12:38:01PM +0100, Greg Kroah-Hartman wrote: > > >> On Tue, Jan 04, 2022 at 12:13:06PM +0100, Tomasz Mo=C5=84 wrote: > > >>> On 04.01.2022 11:54, Greg Kroah-Hartman wrote: > > >>>> Why can't you do this dynamically based on the baud rate so as to = always > > >>>> work properly for all speeds without increased delays for slower o= nes? > > >>> > > >>> Could you please advise on which baud rates to consider as slow? Do= es it > > >>> sound good to have the old trigger level for rates up to and includ= ing > > >>> 115200 and the new one for faster ones? > > >> > > >> You tell me, you are the one seeing this issue and are seeing delays= on > > >> slower values with your change. Do some testing to see where the cu= rve > > >> is. > >=20 > > While the increased latency due to this change is undeniable, it is > > important to note that latency is not everything. There are applications > > where the latency is crucial, however using Linux for such applications > > is questionable. Linux is not a Real Time Operating System after all. >=20 > Yes, Linux can be used in real time situtations just fine, look at the > RT patchset for proof of that. >=20 > So let's not make things any worse for no good reason if at all > possible. +1 We have a $CUSTOMER, where serial latency is crucial. And we have a task to cut down latencies and jitter even more. Marc --=20 Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | --5wlq3p55oytqdc3h Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEK3kIWJt9yTYMP3ehqclaivrt76kFAmHVeXsACgkQqclaivrt 76l+Qwf/YWitn8APufBNgU4+dgTHNsMK5ArklPxAAK37cD3Dn+S1ATaRiRFzMcMV QemXYKmsdP2A+lN0RF+poNpeXORKWP3DUIVx6YiBxqzpkYeKRBKOCHC8bBtGzpmX RGLMDYPqv9VPJDpuFD/gBaDPum0p9sz+bph0Z43DlUTAAotKT926FJHiZGKwpYk/ +QoOrCAwdoemv83zrASaKeRvLgiVsiRYbRaPABkkFq5YOWnmPYf6lKzxuUE1gfwb KdtsBpIVz4HWViMmcG4oLrHDqKP9pvxZOxNB47nchoEMJpGBYleJzH+7rBgS9Az6 sxEhetc2Ik1PPzBv8wJdExpmpGibIQ== =UEzv -----END PGP SIGNATURE----- --5wlq3p55oytqdc3h--