From patchwork Tue Dec 5 03:22:28 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nick Bowler X-Patchwork-Id: 10092501 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 8AEC66035E for ; Tue, 5 Dec 2017 08:50:36 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7AD7629500 for ; Tue, 5 Dec 2017 08:50:36 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6FB1129511; Tue, 5 Dec 2017 08:50:36 +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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 1257F29500 for ; Tue, 5 Dec 2017 08:50:36 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 19D4B6E445; Tue, 5 Dec 2017 08:49:54 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail3.start.ca (mail3.start.ca [IPv6:2600:1611:1::e:3]) by gabe.freedesktop.org (Postfix) with ESMTPS id EF8318990D for ; Tue, 5 Dec 2017 03:22:35 +0000 (UTC) Received: from localhost (ip-24-156-181-89.user.start.ca [24.156.181.89]) by mail3.start.ca (8.14.4/8.14.4/) with ESMTP id vB53MStr009424 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 4 Dec 2017 22:22:28 -0500 Date: Mon, 4 Dec 2017 22:22:28 -0500 From: Nick Bowler To: Laurent Pinchart Subject: Re: PROBLEM: Asus C201 video mode problems on HDMI hotplug (regression) Message-ID: <20171205032228.m62nquqgrnswfbxl@aura.draconx.ca> References: <1710500.fZbdeDGCTu@avalon> <20171204193001.dduxkafufgpeexk2@aura.draconx.ca> <2033574.q3E8txTlp8@avalon> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <2033574.q3E8txTlp8@avalon> User-Agent: NeoMutt/20171027 X-Mailman-Approved-At: Tue, 05 Dec 2017 08:49:51 +0000 Cc: Jose Abreu , Laurent Pinchart , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Dave Airlie , Linus Torvalds X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP On 2017-12-04 21:34 +0200, Laurent Pinchart wrote: > On Monday, 4 December 2017 21:30:01 EET Nick Bowler wrote: > > On 2017-12-04 21:06 +0200, Laurent Pinchart wrote: > > > As you reported that the PLL lock failure message is not printed, the > > > failure can only come from either the extra delay introduced by the > > > above loop, or from reading the HDMI_PHY_STAT0 register. > > > > > > How many iterations of the for loop execute before the condition > > > becomes true? > > > > Judging from the log posted elsethread (where I added extra printouts), > > it seems to consistently become true on the second iteration. > > > > I will try to rule out read side effects by replacing the polling loop > > with an unconditional delay. > > You're reading my mind :-) I did this test by applying the following patch on 4.15-rc1, and the problem remains. So it appears the delay is responsible somehow. Cheers, Nick diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c index bf14214fa464..4aec4d5c130e 100644 --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c @@ -1101,8 +1101,6 @@ static void dw_hdmi_phy_power_off(struct dw_hdmi *hdmi) static int dw_hdmi_phy_power_on(struct dw_hdmi *hdmi) { const struct dw_hdmi_phy_data *phy = hdmi->phy.data; - unsigned int i; - u8 val; if (phy->gen == 1) { dw_hdmi_phy_enable_powerdown(hdmi, false); @@ -1116,21 +1114,7 @@ static int dw_hdmi_phy_power_on(struct dw_hdmi *hdmi) dw_hdmi_phy_gen2_txpwron(hdmi, 1); dw_hdmi_phy_gen2_pddq(hdmi, 0); - /* Wait for PHY PLL lock */ - for (i = 0; i < 5; ++i) { - val = hdmi_readb(hdmi, HDMI_PHY_STAT0) & HDMI_PHY_TX_PHY_LOCK; - if (val) - break; - - usleep_range(1000, 2000); - } - - if (!val) { - dev_err(hdmi->dev, "PHY PLL failed to lock\n"); - return -ETIMEDOUT; - } - - dev_dbg(hdmi->dev, "PHY PLL locked %u iterations\n", i); + usleep_range(1000, 2000); return 0; }