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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 7AD0CC0044D for ; Mon, 16 Mar 2020 07:26:29 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 504E120663 for ; Mon, 16 Mar 2020 07:26:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="LfsfZf77" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 504E120663 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=bGyQGv4xb1XNsDfT91qWSyksvV0g+b8GFtfz6yy8t/c=; b=LfsfZf77mwwuQL kg8+171yfxcLdDnzPO/GXsNRojVb89CnHgNIAY7s4U48E+PKw2bYnPFnE6Z8IcF0OUkeQkUclK3xA nXDu4AnRPw01Z5g//OQ0VFT9pFDAduusRqE95vpGmif38Q5fpAVB22UFq4IaI55cD8dIqqxI3i1Pm gN7eTe/uCjt6C5cLdphu4AWHrva0biHA9orsft7nw9c12JAUAtTykGcD3r+p98+4EEv+ci0hr/O1X cxvtczoH5TghD1I1qKlw4Ju2a8msXqJWPZE6l3FuwdI9GoMF6kO4Hg4sDp0O1YD8A3OTrciH7Vs6Q Smz2WfyVbOR81/M/rrlw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jDk8o-0006Ad-LE; Mon, 16 Mar 2020 07:26:26 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jDk8k-00069u-Sh for linux-arm-kernel@lists.infradead.org; Mon, 16 Mar 2020 07:26:24 +0000 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 1jDk8e-0006VD-7S; Mon, 16 Mar 2020 08:26:16 +0100 Received: from ukl by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1jDk8b-0003K3-GS; Mon, 16 Mar 2020 08:26:13 +0100 Date: Mon, 16 Mar 2020 08:26:13 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Pascal Roeleven Subject: Re: pwm: sun4i: pwm-backlight not working since 5.6-rc1 Message-ID: <20200316072613.37lnjfloac4npudf@pengutronix.de> References: <6185b5540ca082d887d7d13330c9d938@pascalroeleven.nl> <20200312132942.2kfspvmoc3mxkdx4@pengutronix.de> <6e995c4c22c4e6c93acb1f491e5aa109@pascalroeleven.nl> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <6e995c4c22c4e6c93acb1f491e5aa109@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-arm-kernel@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200316_002622_928259_5DD41402 X-CRM114-Status: GOOD ( 24.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-pwm@vger.kernel.org, linux-sunxi@googlegroups.com, linux-kernel@vger.kernel.org, Maxime Ripard , Chen-Yu Tsai , Thierry Reding , Philipp Zabel , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hello, On Thu, Mar 12, 2020 at 04:06:07PM +0100, Pascal Roeleven wrote: > On 2020-03-12 14:29, Uwe Kleine-K=F6nig wrote: > > 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 > = > Thanks for your response. > = > Yes I am sure that is the commit. If I am on master, and replace pwm-sun4= i.c > with the one from 5b090b43, everything works. If I then apply fa4d8178, it > stops working. > = > And strangely the output of the registers is exactly the same before and > after fa4d8178: > = > 01c20e00: 00000050 00130014 00000000 (full brightness) > 01c20e00: 00000050 00130006 00000000 (min brightness) > = > Even when I'm on 5b090b43 and cherry-pick fa4d8178 can I reproduce the > issue. Very strange. I'm out of sensible ideas. The remaining ones are: - enable tracing in the kernel and boot with trace_event=3Dpwm And then check after the problem occurred in /sys/kernel/debug/tracing/trace if something sticks out. - Try modifying the registers using memtool. E.g. memtool mw 0x01c20e04 0x00130012 - Do you have equipment to check the actual output of the PWM hardware? If so, what do you see? Best regards Uwe -- = Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | https://www.pengutronix.de/ | _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel