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 X-Spam-Level: X-Spam-Status: No, score=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 213E3C3526F for ; Fri, 18 Dec 2020 20:45:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E065F23B6C for ; Fri, 18 Dec 2020 20:45:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387710AbgLRUpL (ORCPT ); Fri, 18 Dec 2020 15:45:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:49504 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387682AbgLRUpJ (ORCPT ); Fri, 18 Dec 2020 15:45:09 -0500 Date: Fri, 18 Dec 2020 20:44:14 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1608324268; bh=FHEoFO/2rytdu5VZklTtZU1f7kCAwk3tI8XN0yShfQE=; h=From:To:Cc:Subject:References:In-Reply-To:From; b=KZPRtXDdss7HGtCia5eE0SJHMLLhwGKB/QXjxvxiktZB62FEpBkARwWJpyyjEVyyL cPhVzxuOF9JMe42dr0DzoNGXwV94nHs48+9bwBjgQO01AKjuu+rLuDPCljC1Y269wU JNu2YMWf212sH/04HnmhcN3g1MiH5PfE8eZdnV/lJ6y4kGfkhA85LfGUqV6K6twpWA /QULPHoGrwDIar4pWhSUP7J+RDeKUnHot2jrrGShNPULRL6VoMj460Nuc8dn1DSxWA sgpHO5wFYXz8YtIMDkP9Zo4bDuuI9V8iHDUsay0ZbQl6WAxdDZ2sMJvzquIC4FFnRF eokbjuqrE1hyg== From: Mark Brown To: Pratyush Yadav Cc: Sowjanya Komatineni , Boris Brezillon , thierry.reding@gmail.com, jonathanh@nvidia.com, robh+dt@kernel.org, lukas@wunner.de, bbrezillon@kernel.org, tudor.ambarus@microchip.com, linux-spi@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org Subject: Re: [PATCH v4 5/9] spi: spi-mem: Mark dummy transfers by setting dummy_data bit Message-ID: <20201218204414.GG5333@sirena.org.uk> References: <1608236927-28701-1-git-send-email-skomatineni@nvidia.com> <1608236927-28701-6-git-send-email-skomatineni@nvidia.com> <20201218092106.skwej2g6bk3oksbb@ti.com> <20201218105759.43789ccf@collabora.com> <31c395ee-d7a6-edc5-a790-89fad91a0a27@nvidia.com> <20201218191936.hb6sq7zr3zdirar7@ti.com> <20201218204102.GF5333@sirena.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="Sw7tCqrGA+HQ0/zt" Content-Disposition: inline In-Reply-To: <20201218204102.GF5333@sirena.org.uk> X-Cookie: Password: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --Sw7tCqrGA+HQ0/zt Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Dec 18, 2020 at 08:41:02PM +0000, Mark Brown wrote: > On Sat, Dec 19, 2020 at 12:49:38AM +0530, Pratyush Yadav wrote: > > Anyway, if the SPI maintainers think this is worth it, I won't object. > This gets kind of circular, for me it's a question of if there's some > meaningful benefit from using the feature vs the cost to support it and > from the sounds of it we don't have numbers on the benefits from using > it at present. ...although I do have to say looking at the implementation that the cost seems low, it's just a flag set on an existing transfer. The only issue is if we'd get more win from coalesing the entire transaction (or entire transmit) into a single transfer that could be DMAed and/or requires fewer trips through the stack which does make it seem like an unclear tradeoff from the point of view of client drivers --Sw7tCqrGA+HQ0/zt Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAl/dFJ4ACgkQJNaLcl1U h9CG+Af9EpkMpglPLVubuN097h2axmsNXo9hXZa/vbZu+hYPoNUkicGdmvuK6xpO uPgtkvPbrwCqa/vzYbcvnGFxd7GTbSsOKxYIJgeGP+cCwsvCBPdt15zwL3xjqsEt BNpwz/gHAs4+bTzDW82ZN7Iwiqmeh0cUUjAZwRNo2LZOOopGIfdFh6bH47dVin9z Bwe70eRv98kRcEkXf86TTk2+Y10L2u6sp4B4gPgscggvq41gtUrOEYo+vNg5FZna RYwS5OGLRf41mS5TGr/jx/vefhcm1Mz8g5Bmb5KDNPWhP/QbY+I24F6GrNhr85zV lyAHbpBOa0twJHc051myuf9+SkbyBg== =6aAL -----END PGP SIGNATURE----- --Sw7tCqrGA+HQ0/zt--