From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752994AbcDRRDf (ORCPT ); Mon, 18 Apr 2016 13:03:35 -0400 Received: from lists.s-osg.org ([54.187.51.154]:60960 "EHLO lists.s-osg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751420AbcDRRDd (ORCPT ); Mon, 18 Apr 2016 13:03:33 -0400 Subject: Re: [PATCH v2] regulator: s2mps11: Set default ramp delay for S2MPS11 LDOs To: Krzysztof Kozlowski , Sangbeom Kim , Liam Girdwood , Mark Brown , Lee Jones , linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org References: <1460986390-9674-1-git-send-email-k.kozlowski@samsung.com> Cc: Bartlomiej Zolnierkiewicz From: Javier Martinez Canillas Message-ID: <5715135A.4010402@osg.samsung.com> Date: Mon, 18 Apr 2016 13:03:22 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.1 MIME-Version: 1.0 In-Reply-To: <1460986390-9674-1-git-send-email-k.kozlowski@samsung.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Krzysztof, On 04/18/2016 09:33 AM, Krzysztof Kozlowski wrote: > Driver did not provide default value for ramp delay for LDOs which lead > to warning in dmesg, e.g. on Odroid XU4: > > [ 1.486076] vdd_ldo9: ramp_delay not set > [ 1.506875] vddq_mmc2: ramp_delay not set > [ 1.523766] vdd_ldo15: ramp_delay not set > [ 1.544702] vdd_sd: ramp_delay not set > > The datasheet for all the S2MPS1x family is inconsistent here and does > not specify unambiguously the value of ramp delay for LDO. It mentions > 30 mV/us in one timing diagram but then omits it completely in LDO > regulator characteristics table (it is specified for bucks). > > However the vendor kernels for Galaxy S5 and Odroid XU3 use values of 12 > mV/us or 24 mV/us. > > Without the ramp delay value the consumers do not wait for voltage > settle after changing it. Although the proper value of ramp delay for > LDOs is unknown, it seems safer to use at least some value from > reference kernel than to leave it unset. > > Signed-off-by: Krzysztof Kozlowski > Reviewed-by: Javier Martinez Canillas Best regards, -- Javier Martinez Canillas Open Source Group Samsung Research America