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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 9BD21C433FE for ; Thu, 17 Nov 2022 10:59:59 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7984D10E07E; Thu, 17 Nov 2022 10:59:58 +0000 (UTC) Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9632F10E07E for ; Thu, 17 Nov 2022 10:59:55 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id CE96A60BA6; Thu, 17 Nov 2022 10:59:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C113CC433D6; Thu, 17 Nov 2022 10:59:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668682794; bh=FTcXBVf4xKuIE7vas46JjAXZsr5dkNSkrqRgK59BR3E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=j3aCJYHiEH9yeDG4sHk7/Z9AsxDyOnRrOuUaaPmyFhDe4xZ7640/EoC+qQ21H+kXH 08J0YkV0AvOWwkIZgeORvNcR7+Thk9/gFhQ+j/07CgdiSiqgHT9sIkpbJnlNSmSYy7 F0s+Lkp/tCo9flUPLLLEOsKv77nTk0+dt8r9HQwPWNuFFrKmTl0g1PmuMnTR1dHuFK +EIKV6Bz/yqgXNyld4b+aneK1HPLhq8HFjHJiNQnrXiCMqPg/W7GwFnmcAzJ9Q24D4 g/OdUB4RLlrAVnEBDmQqm2/TGfn+5SaqpKMM4hfxrlG03xxcvz/cnqRwwzEEYNWBF6 8Rz0l/MIOY8Kg== Date: Thu, 17 Nov 2022 10:59:50 +0000 From: Mark Brown To: Carlo Caione Subject: Re: [PATCH 3/3] spi: meson-spicc: Lower CS between bursts Message-ID: References: <20221116-s905x_spi_ili9486-v1-0-630401cb62d5@baylibre.com> <20221116-s905x_spi_ili9486-v1-3-630401cb62d5@baylibre.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="sVW5maJnbV5GYFNa" Content-Disposition: inline In-Reply-To: <20221116-s905x_spi_ili9486-v1-3-630401cb62d5@baylibre.com> X-Cookie: Ego sum ens omnipotens. X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Neil Armstrong , Martin Blumenstingl , Kevin Hilman , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-spi@vger.kernel.org, linux-amlogic@lists.infradead.org, Kamlesh Gurudasani , linux-arm-kernel@lists.infradead.org, Jerome Brunet Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" --sVW5maJnbV5GYFNa Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Nov 17, 2022 at 09:47:41AM +0100, Carlo Caione wrote: > On some hardware (reproduced on S905X) when a large payload is > transmitted over SPI in bursts at the end of each burst, the clock line > briefly fluctuates creating spurious clock transitions that are being > recognised by the connected device as a genuine pulses, creating an > offset in the data being transmitted. > Lower the GPIO CS between bursts to avoid the clock being interpreted as > valid. This is just plain broken, *many* SPI devices attach meaning to chip select edges - for example register writes will typically have the register address followed by one or more register values for sequential registers. Bouncing chip select in the middle of transfer will corrupt data. If the device can't handle larger transfers it needs to advertise this limit and refuse to handle them. --sVW5maJnbV5GYFNa Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmN2FCYACgkQJNaLcl1U h9BA1Af9GvKfza2vtRbu0JnM9pTzjygGkt+vf4n801Z7oafMH+9AsCMpa4yyr7Dq zhMWNsKInloF+p+FGqJUx6iky4xR83YXfpR1dzXn9xh27MNjYMSvH9MgbDLKKPyZ TG+uVFrFsaus8eR7mzZw80l7KCiw6ypiGWh5o+qtO7UWGCVnbcwl1NeD0RDolNE+ tmRoPMEoZohX3XIGL5NGihK0buq/ZFq4EkrpUK7mfJ5kHSCwtX7O4ZR4SUI2VB8g WiLut2anQJ/MgXPdHnhKdrY47fwGRDi3TCI88Le+mb2gc3iUAf4r1rdqviUnMps7 6nf/3APDiJ0vw09mztpBv8KT1ASrrg== =atc7 -----END PGP SIGNATURE----- --sVW5maJnbV5GYFNa-- 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 4B10DC43217 for ; Thu, 17 Nov 2022 11:02:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239769AbiKQLBz (ORCPT ); Thu, 17 Nov 2022 06:01:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48014 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239647AbiKQLAk (ORCPT ); Thu, 17 Nov 2022 06:00:40 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 004BB1C7; Thu, 17 Nov 2022 02:59:56 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 7F8BCB81FF4; Thu, 17 Nov 2022 10:59:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C113CC433D6; Thu, 17 Nov 2022 10:59:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668682794; bh=FTcXBVf4xKuIE7vas46JjAXZsr5dkNSkrqRgK59BR3E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=j3aCJYHiEH9yeDG4sHk7/Z9AsxDyOnRrOuUaaPmyFhDe4xZ7640/EoC+qQ21H+kXH 08J0YkV0AvOWwkIZgeORvNcR7+Thk9/gFhQ+j/07CgdiSiqgHT9sIkpbJnlNSmSYy7 F0s+Lkp/tCo9flUPLLLEOsKv77nTk0+dt8r9HQwPWNuFFrKmTl0g1PmuMnTR1dHuFK +EIKV6Bz/yqgXNyld4b+aneK1HPLhq8HFjHJiNQnrXiCMqPg/W7GwFnmcAzJ9Q24D4 g/OdUB4RLlrAVnEBDmQqm2/TGfn+5SaqpKMM4hfxrlG03xxcvz/cnqRwwzEEYNWBF6 8Rz0l/MIOY8Kg== Date: Thu, 17 Nov 2022 10:59:50 +0000 From: Mark Brown To: Carlo Caione Cc: Kamlesh Gurudasani , Neil Armstrong , Jerome Brunet , David Airlie , Martin Blumenstingl , Kevin Hilman , Daniel Vetter , linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH 3/3] spi: meson-spicc: Lower CS between bursts Message-ID: References: <20221116-s905x_spi_ili9486-v1-0-630401cb62d5@baylibre.com> <20221116-s905x_spi_ili9486-v1-3-630401cb62d5@baylibre.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="sVW5maJnbV5GYFNa" Content-Disposition: inline In-Reply-To: <20221116-s905x_spi_ili9486-v1-3-630401cb62d5@baylibre.com> X-Cookie: Ego sum ens omnipotens. Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --sVW5maJnbV5GYFNa Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Nov 17, 2022 at 09:47:41AM +0100, Carlo Caione wrote: > On some hardware (reproduced on S905X) when a large payload is > transmitted over SPI in bursts at the end of each burst, the clock line > briefly fluctuates creating spurious clock transitions that are being > recognised by the connected device as a genuine pulses, creating an > offset in the data being transmitted. > Lower the GPIO CS between bursts to avoid the clock being interpreted as > valid. This is just plain broken, *many* SPI devices attach meaning to chip select edges - for example register writes will typically have the register address followed by one or more register values for sequential registers. Bouncing chip select in the middle of transfer will corrupt data. If the device can't handle larger transfers it needs to advertise this limit and refuse to handle them. --sVW5maJnbV5GYFNa Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmN2FCYACgkQJNaLcl1U h9BA1Af9GvKfza2vtRbu0JnM9pTzjygGkt+vf4n801Z7oafMH+9AsCMpa4yyr7Dq zhMWNsKInloF+p+FGqJUx6iky4xR83YXfpR1dzXn9xh27MNjYMSvH9MgbDLKKPyZ TG+uVFrFsaus8eR7mzZw80l7KCiw6ypiGWh5o+qtO7UWGCVnbcwl1NeD0RDolNE+ tmRoPMEoZohX3XIGL5NGihK0buq/ZFq4EkrpUK7mfJ5kHSCwtX7O4ZR4SUI2VB8g WiLut2anQJ/MgXPdHnhKdrY47fwGRDi3TCI88Le+mb2gc3iUAf4r1rdqviUnMps7 6nf/3APDiJ0vw09mztpBv8KT1ASrrg== =atc7 -----END PGP SIGNATURE----- --sVW5maJnbV5GYFNa-- 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 AEFE8C4332F for ; Thu, 17 Nov 2022 11:09:36 +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:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: 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=gW5ImMuxv+pOLLBYf06LV7nAYy2MjOIoRpIIYOgltzs=; b=wi81h20vA/1GtJJpSKFvk8h4AN +fqC2lS+oPfd4Uu4IGomY33OQdKZ7rzRXMBZOQmxtUTBBZcK59Tj4WqIZ1N7NGn3jPZcH1XzErFB3 s3xfKjj+Y9O8f02V538h4qrpEKzb/9Vo3WVQsfUsJFUcx1o/fWq9tD/VG1Dv5PltoIdmu3L3OQMJh Sdo98/Vfv7dIQQR6vsj156s7Ck6SwH+JhjrLrrGBBjf1DjPd/8xHPRyICT1+Zqy2WpZaIQFv/tgZj DzO+l8KWW4hdiNuZ5huxIVWbvDCyBK5xZYx7wc6ZcRRiY0S0Vgj9eTtaMqF+igQNbujtTAvm+M2kV aA8BzKLA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ovclp-00CyFq-5O; Thu, 17 Nov 2022 11:09:25 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ovccd-00CsJU-Hg; Thu, 17 Nov 2022 10:59:56 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id CE96A60BA6; Thu, 17 Nov 2022 10:59:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C113CC433D6; Thu, 17 Nov 2022 10:59:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668682794; bh=FTcXBVf4xKuIE7vas46JjAXZsr5dkNSkrqRgK59BR3E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=j3aCJYHiEH9yeDG4sHk7/Z9AsxDyOnRrOuUaaPmyFhDe4xZ7640/EoC+qQ21H+kXH 08J0YkV0AvOWwkIZgeORvNcR7+Thk9/gFhQ+j/07CgdiSiqgHT9sIkpbJnlNSmSYy7 F0s+Lkp/tCo9flUPLLLEOsKv77nTk0+dt8r9HQwPWNuFFrKmTl0g1PmuMnTR1dHuFK +EIKV6Bz/yqgXNyld4b+aneK1HPLhq8HFjHJiNQnrXiCMqPg/W7GwFnmcAzJ9Q24D4 g/OdUB4RLlrAVnEBDmQqm2/TGfn+5SaqpKMM4hfxrlG03xxcvz/cnqRwwzEEYNWBF6 8Rz0l/MIOY8Kg== Date: Thu, 17 Nov 2022 10:59:50 +0000 From: Mark Brown To: Carlo Caione Cc: Kamlesh Gurudasani , Neil Armstrong , Jerome Brunet , David Airlie , Martin Blumenstingl , Kevin Hilman , Daniel Vetter , linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH 3/3] spi: meson-spicc: Lower CS between bursts Message-ID: References: <20221116-s905x_spi_ili9486-v1-0-630401cb62d5@baylibre.com> <20221116-s905x_spi_ili9486-v1-3-630401cb62d5@baylibre.com> MIME-Version: 1.0 In-Reply-To: <20221116-s905x_spi_ili9486-v1-3-630401cb62d5@baylibre.com> X-Cookie: Ego sum ens omnipotens. X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221117_025955_654503_B12D5641 X-CRM114-Status: GOOD ( 14.67 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============2913346145751894704==" Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org --===============2913346145751894704== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="sVW5maJnbV5GYFNa" Content-Disposition: inline --sVW5maJnbV5GYFNa Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Nov 17, 2022 at 09:47:41AM +0100, Carlo Caione wrote: > On some hardware (reproduced on S905X) when a large payload is > transmitted over SPI in bursts at the end of each burst, the clock line > briefly fluctuates creating spurious clock transitions that are being > recognised by the connected device as a genuine pulses, creating an > offset in the data being transmitted. > Lower the GPIO CS between bursts to avoid the clock being interpreted as > valid. This is just plain broken, *many* SPI devices attach meaning to chip select edges - for example register writes will typically have the register address followed by one or more register values for sequential registers. Bouncing chip select in the middle of transfer will corrupt data. If the device can't handle larger transfers it needs to advertise this limit and refuse to handle them. --sVW5maJnbV5GYFNa Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmN2FCYACgkQJNaLcl1U h9BA1Af9GvKfza2vtRbu0JnM9pTzjygGkt+vf4n801Z7oafMH+9AsCMpa4yyr7Dq zhMWNsKInloF+p+FGqJUx6iky4xR83YXfpR1dzXn9xh27MNjYMSvH9MgbDLKKPyZ TG+uVFrFsaus8eR7mzZw80l7KCiw6ypiGWh5o+qtO7UWGCVnbcwl1NeD0RDolNE+ tmRoPMEoZohX3XIGL5NGihK0buq/ZFq4EkrpUK7mfJ5kHSCwtX7O4ZR4SUI2VB8g WiLut2anQJ/MgXPdHnhKdrY47fwGRDi3TCI88Le+mb2gc3iUAf4r1rdqviUnMps7 6nf/3APDiJ0vw09mztpBv8KT1ASrrg== =atc7 -----END PGP SIGNATURE----- --sVW5maJnbV5GYFNa-- --===============2913346145751894704== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic --===============2913346145751894704==-- 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 7E836C433FE for ; Thu, 17 Nov 2022 11:10:53 +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:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: 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=W5tcahgR3k/+M/43aDjSRSKSCbEZvdbF+JBXT0yyYgI=; b=zBQdqEjMT9fStFVdOK3rwtFWkG 5OzNXGVDUYITXenwP9J98eRa7OkcshTN1qDzk+drcUquUkc7w/+dzqAqgUyI1ETtZagKSTr1Ojpus R100sZ20MGQGJ4vt6qbekzUJCrmgTrSmGY5YrFI6y8Mpd2W8Jac6W4nTpve7UA4H4sROoiuze+vle K382FTFNSrfceseZcA5niEf1lbZCS+m40RzBdXVLoZe7wWAMLPQ3O+tnFuvALivkicAK8bxwBukql yJ+O1STvP1IPxjJ1fH0wUdRspURPHMMhLaaAPyVOXkJODiRRpJLuJYFxCwqZnLIfcuQBfhDCu7sUr I8dAADXQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ovcls-00CyIJ-AM; Thu, 17 Nov 2022 11:09:28 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ovccd-00CsJU-Hg; Thu, 17 Nov 2022 10:59:56 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id CE96A60BA6; Thu, 17 Nov 2022 10:59:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C113CC433D6; Thu, 17 Nov 2022 10:59:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668682794; bh=FTcXBVf4xKuIE7vas46JjAXZsr5dkNSkrqRgK59BR3E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=j3aCJYHiEH9yeDG4sHk7/Z9AsxDyOnRrOuUaaPmyFhDe4xZ7640/EoC+qQ21H+kXH 08J0YkV0AvOWwkIZgeORvNcR7+Thk9/gFhQ+j/07CgdiSiqgHT9sIkpbJnlNSmSYy7 F0s+Lkp/tCo9flUPLLLEOsKv77nTk0+dt8r9HQwPWNuFFrKmTl0g1PmuMnTR1dHuFK +EIKV6Bz/yqgXNyld4b+aneK1HPLhq8HFjHJiNQnrXiCMqPg/W7GwFnmcAzJ9Q24D4 g/OdUB4RLlrAVnEBDmQqm2/TGfn+5SaqpKMM4hfxrlG03xxcvz/cnqRwwzEEYNWBF6 8Rz0l/MIOY8Kg== Date: Thu, 17 Nov 2022 10:59:50 +0000 From: Mark Brown To: Carlo Caione Cc: Kamlesh Gurudasani , Neil Armstrong , Jerome Brunet , David Airlie , Martin Blumenstingl , Kevin Hilman , Daniel Vetter , linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH 3/3] spi: meson-spicc: Lower CS between bursts Message-ID: References: <20221116-s905x_spi_ili9486-v1-0-630401cb62d5@baylibre.com> <20221116-s905x_spi_ili9486-v1-3-630401cb62d5@baylibre.com> MIME-Version: 1.0 In-Reply-To: <20221116-s905x_spi_ili9486-v1-3-630401cb62d5@baylibre.com> X-Cookie: Ego sum ens omnipotens. X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221117_025955_654503_B12D5641 X-CRM114-Status: GOOD ( 14.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============6747875612799983720==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============6747875612799983720== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="sVW5maJnbV5GYFNa" Content-Disposition: inline --sVW5maJnbV5GYFNa Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Nov 17, 2022 at 09:47:41AM +0100, Carlo Caione wrote: > On some hardware (reproduced on S905X) when a large payload is > transmitted over SPI in bursts at the end of each burst, the clock line > briefly fluctuates creating spurious clock transitions that are being > recognised by the connected device as a genuine pulses, creating an > offset in the data being transmitted. > Lower the GPIO CS between bursts to avoid the clock being interpreted as > valid. This is just plain broken, *many* SPI devices attach meaning to chip select edges - for example register writes will typically have the register address followed by one or more register values for sequential registers. Bouncing chip select in the middle of transfer will corrupt data. If the device can't handle larger transfers it needs to advertise this limit and refuse to handle them. --sVW5maJnbV5GYFNa Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmN2FCYACgkQJNaLcl1U h9BA1Af9GvKfza2vtRbu0JnM9pTzjygGkt+vf4n801Z7oafMH+9AsCMpa4yyr7Dq zhMWNsKInloF+p+FGqJUx6iky4xR83YXfpR1dzXn9xh27MNjYMSvH9MgbDLKKPyZ TG+uVFrFsaus8eR7mzZw80l7KCiw6ypiGWh5o+qtO7UWGCVnbcwl1NeD0RDolNE+ tmRoPMEoZohX3XIGL5NGihK0buq/ZFq4EkrpUK7mfJ5kHSCwtX7O4ZR4SUI2VB8g WiLut2anQJ/MgXPdHnhKdrY47fwGRDi3TCI88Le+mb2gc3iUAf4r1rdqviUnMps7 6nf/3APDiJ0vw09mztpBv8KT1ASrrg== =atc7 -----END PGP SIGNATURE----- --sVW5maJnbV5GYFNa-- --===============6747875612799983720== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============6747875612799983720==--