From mboxrd@z Thu Jan 1 00:00:00 1970 From: Felipe Balbi Subject: Re: [RFC/NOT FOR MERGING] HACK: add global/private timers for A9 Date: Wed, 3 Jun 2015 16:28:21 -0500 Message-ID: <20150603212821.GH6042@saruman.tx.rr.com> References: <1433363565-17725-1-git-send-email-balbi@ti.com> <2466648.WjMxjIpAUG@wuerfel> <20150603210455.GD6042@saruman.tx.rr.com> Reply-To: Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="4BlIp4fARb6QCoOq" Return-path: Received: from devils.ext.ti.com ([198.47.26.153]:54257 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753374AbbFCVbM (ORCPT ); Wed, 3 Jun 2015 17:31:12 -0400 Content-Disposition: inline In-Reply-To: <20150603210455.GD6042@saruman.tx.rr.com> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Felipe Balbi Cc: Arnd Bergmann , linux-arm-kernel@lists.infradead.org, Tony Lindgren , Russell King , Linux OMAP Mailing List , Shawn Guo --4BlIp4fARb6QCoOq Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jun 03, 2015 at 04:04:55PM -0500, Felipe Balbi wrote: > On Wed, Jun 03, 2015 at 10:55:27PM +0200, Arnd Bergmann wrote: > > On Wednesday 03 June 2015 15:32:45 Felipe Balbi wrote: > > >=20 > > > Hi Tony and Russell, > > >=20 > > > AM43xx, even though it's a single processor A9, it still has TWD and = global > > > timer. I was doing some profiling with RT v4.0 and latency is 3.5x lo= wer just > > > by switching from gptimer to twd/global. > > >=20 > > > The only problem is that currently, is_smp() check prevents me from u= sing twd > > > with AM43xx (that's why it's commented below, for testing purposes). > > >=20 > > > In the hopes that we can start a, hopefully, small thread around the = subject, > > > I'm sending this HACK which I used to get TWD and global timer enable= d so I > > > could measure latencies with cyclictest. > > >=20 > > > Is it so that TWD shouldn't be available on UP integrations of ARM's = Cortex-A > > > processors ? > > >=20 > > >=20 > >=20 > > I wondered about this recently when looking at something unrelated > > and noticed that the check had been introduced as part of > > 904464b91eca8 ("ARM: 7655/1: smp_twd: make twd_local_timer_of_register() > > no-op for nosmp"). > >=20 > > I suspect this was just the wrong fix at the time, and that the > > real culprit is either alloc_percpu() or request_percpu_irq() > > getting called too early on a machine without SMP support. > >=20 > > Possibly the problem is already resolved independently, if you > > didn't run into it. >=20 > no, no splats, nothing at all. See [1] >=20 > [1] http://hastebin.com/helekubutu Adding Shawn --=20 balbi --4BlIp4fARb6QCoOq Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJVb3F1AAoJEIaOsuA1yqRERvUP/irbowNMuAYUHKwJjR33cDPu 3uoNe6dwf3zX8T5J9yepSyR567gKL6TPzZ4gSsWVzyOUJmxZk4VkGg3IEZ3RN6Z2 b4Rhva0JDbcFzyBFBo3MentxiRLprxerFBH/+U0/EJO5MbDWAXuG1Ak3qrhr5ePN dvu+jZOmtLp0L/jw+Fp3vez2QnJiqQX0PUNhASq5Id/P/llbysQaJ2Wd83ucsAJo S2xzLS0UApBdf4F3lIhbz6vi4xNcpHfv93BtMvkqzCHYCc8Kxu/Kou1Ax+Pdc6Hm RiBMD5b3GCnI8cLyMhWk0fd81sB8X3L2z8n9LcOQGalS7JYOaJpKuKKOTeNc9Ooe AAdCtjfMDKmWJD9u7SFhc43CPi+gdtCE4wqCTQx96qq/Be2BEn2NngKhVHF+3fcY 3GXgwVEj/4w7U+8ZNX5ct3seWN1584Gwgj+Y2VWrIe08pvghFQT1xYBVGyPurYyf //TJ327GVIui+c70HsTQMW10jYUHLtTjpsNmmote1iHq3ep6lnS5i508TXOzwYtR rmEcu5MRFe0MuE3kiizvZ5NmWMRxR1XKkymBW6mUMqS3tjwFC1sNHMcRQRFMOY4D tTQhZSlvCIGs127JJr5FoS7ReSl7bfp56Ir5B/DYi7vs9CXRL2hDVkj7ezLDNYfm TeOdZSbah/JjZB2P4zWM =ZkHU -----END PGP SIGNATURE----- --4BlIp4fARb6QCoOq--