From patchwork Wed Jun 15 06:13:31 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "J, KEERTHY" X-Patchwork-Id: 9177613 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id B264E6021C for ; Wed, 15 Jun 2016 06:16:59 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A0FFD27DF9 for ; Wed, 15 Jun 2016 06:16:59 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 94CA328340; Wed, 15 Jun 2016 06:16:59 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 2695627DF9 for ; Wed, 15 Jun 2016 06:16:58 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1bD46G-0006hk-3m; Wed, 15 Jun 2016 06:14:52 +0000 Received: from comal.ext.ti.com ([198.47.26.152]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1bD46C-0006ax-RA for linux-arm-kernel@lists.infradead.org; Wed, 15 Jun 2016 06:14:49 +0000 Received: from dflxv15.itg.ti.com ([128.247.5.124]) by comal.ext.ti.com (8.13.7/8.13.7) with ESMTP id u5F6Dsqx014321; Wed, 15 Jun 2016 01:13:54 -0500 Received: from DLEE70.ent.ti.com (dlemailx.itg.ti.com [157.170.170.113]) by dflxv15.itg.ti.com (8.14.3/8.13.8) with ESMTP id u5F6EKp1008693; Wed, 15 Jun 2016 01:14:20 -0500 Received: from dlep33.itg.ti.com (157.170.170.75) by DLEE70.ent.ti.com (157.170.170.113) with Microsoft SMTP Server id 14.3.294.0; Wed, 15 Jun 2016 01:14:19 -0500 Received: from ula0393675.india.ti.com (ileax41-snat.itg.ti.com [10.172.224.153]) by dlep33.itg.ti.com (8.14.3/8.13.8) with ESMTP id u5F6EDdA013350; Wed, 15 Jun 2016 01:14:14 -0500 From: Keerthy To: Subject: [tiL4.4-P PATCH] ARM: dts: am437x-sk-evm: Reduce i2c0 bus speed for tps65218 Date: Wed, 15 Jun 2016 11:43:31 +0530 Message-ID: <1465971211-15994-1-git-send-email-j-keerthy@ti.com> X-Mailer: git-send-email 1.9.1 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160614_231448_971560_0B7AA2E8 X-CRM114-Status: UNSURE ( 8.48 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, nm@ti.com, d-gerlach@ti.com, j-keerthy@ti.com, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, robh+dt@kernel.org, Franklin S Cooper Jr , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Aparna Balasubramanian Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP From: Dave Gerlach Based on the latest timing specifications for the TPS65218 from the data sheet, http://www.ti.com/lit/ds/symlink/tps65218.pdf, document SLDS206 from November 2014, we must change the i2c bus speed to better fit within the minimum high SCL time required for proper i2c transfer. When running at 400khz, measurements show that SCL spends 0.8125 uS/1.666 uS high/low which violates the requirement for minimum high period of SCL provided in datasheet Table 7.6 which is 1 uS. Switching to 100khz gives us 5 uS/5 uS high/low which both fall above the minimum given values for 100 khz, 4.0 uS/4.7 uS high/low. Without this patch occasionally a voltage set operation from the kernel will appear to have worked but the actual voltage reflected on the PMIC will not have updated, causing problems especially with cpufreq that may update to a higher OPP without actually raising the voltage on DCDC2, leading to a hang. Signed-off-by: Dave Gerlach Signed-off-by: Nishanth Menon Signed-off-by: Franklin S Cooper Jr Signed-off-by: Aparna Balasubramanian Signed-off-by: Keerthy --- arch/arm/boot/dts/am437x-sk-evm.dts | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/boot/dts/am437x-sk-evm.dts b/arch/arm/boot/dts/am437x-sk-evm.dts index 18a3445..5f67001 100644 --- a/arch/arm/boot/dts/am437x-sk-evm.dts +++ b/arch/arm/boot/dts/am437x-sk-evm.dts @@ -490,7 +490,7 @@ status = "okay"; pinctrl-names = "default"; pinctrl-0 = <&i2c0_pins>; - clock-frequency = <400000>; + clock-frequency = <100000>; tps@24 { compatible = "ti,tps65218";