From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754135AbaBDLOl (ORCPT ); Tue, 4 Feb 2014 06:14:41 -0500 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:35119 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750937AbaBDLOb (ORCPT ); Tue, 4 Feb 2014 06:14:31 -0500 Date: Tue, 4 Feb 2014 11:14:23 +0000 From: Mark Brown To: Geert Uytterhoeven Cc: linux-spi@vger.kernel.org, linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven Message-ID: <20140204111423.GT22609@sirena.org.uk> References: <1391508384-5013-1-git-send-email-geert@linux-m68k.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="2cECDj2Pn+L6wlyc" Content-Disposition: inline In-Reply-To: <1391508384-5013-1-git-send-email-geert@linux-m68k.org> X-Cookie: PARDON me, am I speaking ENGLISH? User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: 94.175.92.69 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: Re: [PATCH] spi: rspi: Only enable interrupts when there's a need to wait X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on mezzanine.sirena.org.uk) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --2cECDj2Pn+L6wlyc Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Feb 04, 2014 at 11:06:24AM +0100, Geert Uytterhoeven wrote: > From: Geert Uytterhoeven >=20 > rspi_wait_for_interrupt() unconditionally enables interrupts, even when t= he > wait condition is already satisfied. This causes a high interrupt load (2 > interrupts/byte for full-duplex Single SPI transfers, 1 interrupt/byte for > RSPI with TX Only mode, or QSPI in unidirectional Dual or Quad Transfer > mode). Applied but I am wondering if the interrupts are really worth it in the first place especially at higher clock rates - if you can get completion within a small number of polls it might be more efficient to just do that rather than take interrupts. --2cECDj2Pn+L6wlyc Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJS8MuLAAoJELSic+t+oim9NzYP/Rtjuw4sggCybprd5E7snNbp 27aE/AvUTYstJFGXsBf9aW/H8XlpEKUKDiDGXaDP1Q6TCu2Tg/b9nK1+Ffm11qmj Ak3rKwMqgtC5/2sIPxIJKH10zLyaDFCsDmOkPmVWa3tw92112NhfYWHzI0Klo3gU qXqe7ACIe4JDj796ww14ld0Lj6WX9BVpLxfLbjGVJFkZ60lrxzBWiwXqo6CQ5qBJ 7Z36tBthUPmdREL6OFwYQ5Vf7a/LlSJdqqLBHN257sFYJ2fltP0vUFfLIYpCVRPz R8//kppnIWw9dZMqV3O68m1GXWFPIUpX/vDZikZxdPMstOFJc0l8FEWsu9OTDl/5 VDkuhMiKV6AdfJ7OV/6kcL3bUvsfiXskt8YHsQkU3BJ7abob/NtB8iNxbRVUffOk t4udK9u9UYhlIrfynXYuDiouu9pSq5tFBktUAF64BcQKCq6q+0ANUrhL9tLm632T t37VuA7c/N9F2xlL399kwAgUvhqmGv9f+YDEsHqTdfq82eMd6gGkHPvSJaAvyqgY WS8HY/tiPcMRPtXp8/t9fCMKNiVNGLM5peNlo5plWh/t/VN3PZzFUKY4xOUNO+aN PQgb0m2f1irYBHKW4eZMAvBI/oMDmh/hX2r8oAYUuy8s6b2ExdAlGfUNVf5DW2jV lf96Jl0RBOMUCHHnigpV =kk+a -----END PGP SIGNATURE----- --2cECDj2Pn+L6wlyc--