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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 B51B8C10DCE for ; Thu, 12 Mar 2020 13:29:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 96D89206E7 for ; Thu, 12 Mar 2020 13:29:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727099AbgCLN3y (ORCPT ); Thu, 12 Mar 2020 09:29:54 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:41205 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726028AbgCLN3y (ORCPT ); Thu, 12 Mar 2020 09:29:54 -0400 Received: from pty.hi.pengutronix.de ([2001:67c:670:100:1d::c5]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jCNuC-0007Km-DG; Thu, 12 Mar 2020 14:29:44 +0100 Received: from ukl by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1jCNuA-0001ji-U0; Thu, 12 Mar 2020 14:29:42 +0100 Date: Thu, 12 Mar 2020 14:29:42 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Pascal Roeleven Cc: Thierry Reding , Maxime Ripard , Chen-Yu Tsai , Philipp Zabel , linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com Subject: Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1 Message-ID: <20200312132942.2kfspvmoc3mxkdx4@pengutronix.de> References: <6185b5540ca082d887d7d13330c9d938@pascalroeleven.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <6185b5540ca082d887d7d13330c9d938@pascalroeleven.nl> User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 12, 2020 at 01:22:13PM +0100, Pascal Roeleven wrote: > Hi all, > > I am working on adding an old A10 device to mainline and noticed an issue > when testing on 5.5.8 vs master. > > Since 5.6-rc1, I can't control the brightness of my LCD backlight anymore. > The backlight stays on full brightness instead. I am controlling the > brightness value via sysfs for testing. > > I am not sure if this is a general pwm-sun4i issue or if it is related to > the backlight. However I narrowed it down to one commit for pwm-sun4i: > > fa4d81784681a26bcf7d2a43c6ac5cf991ef28f5 > > If I use pwm-sun4i.c from 5b090b430d750961305030232314b6acdb0102aa on > master, the backlight works fine. Unfortunately, due to my lack of kernel > experience, I can't see how the commit above broke it. Hmm, I cannot see how fa4d81784681a26bcf7d2a43c6ac5cf991ef28f5 breaks this. Looking at the output of git show -b fa4d81784681a26bcf7d2a43c6ac5cf991ef28f5 (i.e. ignoring whitespace changes) I don't see how the behaviour you're reporting can be explained. Are you sure that fa4d81784681a26bcf7d2a43c6ac5cf991ef28f5 is the bad commit? Can you install a tool to inspect register values and check how the affected registers change if you switch kernel versions and/or pwm settings? (e.g. memtool md 0x1c20e00+0xc ) Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |