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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 87FB0D35176 for ; Wed, 1 Apr 2026 11:00:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: List-Subscribe:List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: In-Reply-To:References:To:From:Cc:Subject:Message-Id:Date:Mime-Version: Reply-To:Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date :Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=8uHXqGycrFIr4OO/NjsPLWbs3DMWYd8EeZE4HipKifw=; b=fLDb06B1I8auxI1sLex9zy2pJC pYRBddfd9vLPG8ztMRylHNRbcyPcFnEm3JXKjiUjbsnXdAK1aTO68+Glf1r7TzSBwwCy9ffUBKhfc QVXRV6eusjtiQcWNuA6ynnggJRxOz382Top504MwB6bJUbq9WBRpc4gsHulvxVS54Cl4kmTQm5Z+X iIgPMNNpTxarzBN23o/mtzuf2ImbBGDhMenef6AEpS3eCDKvtzS3brTVw4y1knW/JGznVO9ArNAcW TcbmrwuWhPMGoziRXewyPO1RgCQi+EYBmGPJqGPFG0KuhGschtYvH96oe7//f/+m8gKJBVG7cJfeA gQLGd5kA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w7tJD-0000000EaWr-2SV2; Wed, 01 Apr 2026 11:00:27 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w7tJB-0000000EaWW-47Tv for linux-mtd@lists.infradead.org; Wed, 01 Apr 2026 11:00:26 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 48DBC60126; Wed, 1 Apr 2026 11:00:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1F7EC4CEF7; Wed, 1 Apr 2026 11:00:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775041225; bh=P4gPDzIC37mQ2XU2ES1ReyzNW1zgfb4XNdW83riZvtY=; h=Date:Subject:Cc:From:To:References:In-Reply-To:From; b=sFSPKFYweFFOdfbH0OagWFKdwhTq+1MKRsDYRdV0xhvI13BSdEYfJPfUUliaIsPZ8 59delv7rophLlaAEkA816DG+xemnbsLMn18Z6kK1y4E1ZuyYuvEiMYmsbG4+rvLY3I Qg0dOE9Aeo4I0uV48WTnU4mWriwqWLJfSDHwy6X+fp3uaudWzUyNUbrd3BFgqVMo83 tMI5nivsa18n4OrbifXTgH/cIcjG+hjs8npXnLpiNmTcbPCtrDpksT6Q7eFhIbhR0B +2LuH1JNsqXCPyTqkH3RAMie5qpNbRxJA/H/Fk6ORUkatElASRqgw/y/0ofC3NGIDj UyiGqB+8ucCjg== Mime-Version: 1.0 Date: Wed, 01 Apr 2026 13:00:20 +0200 Message-Id: Subject: Re: [PATCH RFC 6/7] spi: spi-mem: Call spi_set_rx_sampling_point() for each op Cc: "Frieder Schrempf" , "Mark Brown" , "Richard Weinberger" , "Vignesh Raghavendra" , "Han Xu" , "Eberhard Stoll" , "Tudor Ambarus" , "Pratyush Yadav" , , , , , "Santhosh Kumar K" From: "Michael Walle" To: "Miquel Raynal" , "Frieder Schrempf" X-Mailer: aerc 0.20.0 References: <20260303-fsl-qspi-rx-sampling-delay-v1-0-9326bbc492d6@kontron.de> <20260303-fsl-qspi-rx-sampling-delay-v1-6-9326bbc492d6@kontron.de> <87wlzlnioh.fsf@bootlin.com> <87ecl09wtv.fsf@bootlin.com> <633fee13-a397-410f-a595-db95e04b8110@kontron.de> <87ldf881gr.fsf@bootlin.com> <874ilv84j8.fsf@bootlin.com> In-Reply-To: <874ilv84j8.fsf@bootlin.com> X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============6949920430756587931==" Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org --===============6949920430756587931== Content-Type: multipart/signed; boundary=20ef4b1937c524c4b5e1cf3c92e15c2d5ceb7be4f72bca70e5220b66a6c0; micalg=pgp-sha384; protocol="application/pgp-signature" --20ef4b1937c524c4b5e1cf3c92e15c2d5ceb7be4f72bca70e5220b66a6c0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 On Wed Apr 1, 2026 at 10:32 AM CEST, Miquel Raynal wrote: >> Let's say for a worst case scenario a chip has an RX delay of 20ns (the >> highest I've seen in datasheets so far is 8ns). In that case the maximum >> clock we could safely use for reading the ID would be 1/(2*20e-9) =3D >> 25MHz. Do you think it really makes much of a difference if we read the >> ID (only a handful of bytes) at 25MHz or full speed (e. g. 104 MHz)? I >> mean this should be fast enough either way, no? But maybe I'm misjudging >> this. > > I am honestly not a big fan of the global penalty, but I am not totally > opposed either, especially since you just said you only observed 8ns > delays at most. This is 62.5MHz, which is already above what most > designs use, so the penalty would be minimal. What about taking this > approach and see if that fixes most of our use cases? What are the actual numbers we are talking about here? I mean, at least for SPI NOR, we only read the ID *once*. And it takes about 56 bits (command + id length of 6). That is about 2us at 25MHz. I'd guess the setup and the software handling takes far longer than that. -michael --20ef4b1937c524c4b5e1cf3c92e15c2d5ceb7be4f72bca70e5220b66a6c0 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iKgEABMJADAWIQTIVZIcOo5wfU/AngkSJzzuPgIf+AUCacz6xRIcbXdhbGxlQGtl cm5lbC5vcmcACgkQEic87j4CH/jivwF7BfdJ2oJO2K3l5ud626MmhRiz2MLQbewR E5u5gITBAhN2jHdEai/ryzBXc5JvEBklAYCLd3qRamZ8b67NsNkXMP4lXC5UL7VN gh53mq8O5Msc590EhY5l3GZxv8zwbYJGhFU= =FqVe -----END PGP SIGNATURE----- --20ef4b1937c524c4b5e1cf3c92e15c2d5ceb7be4f72bca70e5220b66a6c0-- --===============6949920430756587931== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/ --===============6949920430756587931==--