From patchwork Mon Nov 16 20:07:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 11910697 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=-6.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 CDDFFC55ABD for ; Mon, 16 Nov 2020 20:08:15 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 8161C221FD for ; Mon, 16 Nov 2020 20:08:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="srUaf9bp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8161C221FD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id CC0C86E0EC; Mon, 16 Nov 2020 20:08:14 +0000 (UTC) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by gabe.freedesktop.org (Postfix) with ESMTPS id 8A2226E0EC for ; Mon, 16 Nov 2020 20:08:13 +0000 (UTC) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2399220702; Mon, 16 Nov 2020 20:08:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605557293; bh=pQrf1dmX9ae8/r7MNwZ83pHLz0ABOqnY7bgAmg2B1N8=; h=From:To:Cc:Subject:Date:From; b=srUaf9bpvjb3VSX+Tc0K0/NGfw0kacxmvrA1+Ey1/YE9Z2g3sDbYxmQnGbGN6jkKv zVMNVB2bhp8dSmDlzfWkmwt7NsJNssID73obAULRALeCYdho1BcaL1h4LITjbUkhcQ 12xsEh7+R2FGhnXwlLb1bq7sjYYvGLY5wWjby1mk= Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1keknK-00B7cF-Th; Mon, 16 Nov 2020 20:08:11 +0000 From: Marc Zyngier To: Neil Armstrong , Kevin Hilman Subject: [PATCH 0/4] drm/meson: Module removal fixes Date: Mon, 16 Nov 2020 20:07:40 +0000 Message-Id: <20201116200744.495826-1-maz@kernel.org> X-Mailer: git-send-email 2.28.0 MIME-Version: 1.0 X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: narmstrong@baylibre.com, khilman@baylibre.com, jbrunet@baylibre.com, martin.blumenstingl@googlemail.com, kernel-team@android.com, dri-devel@lists.freedesktop.org, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Martin Blumenstingl , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-amlogic@lists.infradead.org, kernel-team@android.com, linux-arm-kernel@lists.infradead.org, Jerome Brunet Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi all, Having recently moved over to a top-of-the-tree u-boot on one of my VIM3L systems in order to benefit from unrelated improvements (automatic PCIe detection, EFI...), I faced the issue that my kernel would hang like this: [ OK ] Finished Helper to synchronize boot up for ifupdown. [ OK ] Started Rule-based Manager for Device Events and Files. [ 7.114516] VDDCPU: supplied by regulator-dummy [ OK ] Found device /dev/ttyAML0. [ 7.146862] meson-drm ff900000.vpu: Queued 2 outputs on vpu [ 7.169630] fb0: switching to meson-drm-fb from simple [ 7.169944] Console: switching to colour dummy device 80x25 [ 7.179250] meson-drm ff900000.vpu: CVBS Output connector not available and that's it. After some poking around, I figured out that it is in the meson-dw-hdmi module that the CPU was hanging... Reverting to the kernel DT instead of u-boot's papered over it somehow, but it turned out that removing the module (modprobe -r) resulted in a firework. And for every issue I was fixing, another followed. Much fun for a rainy Monday in the basement! I ended up with the following 4 patches, which solve all my problems: I can now boot with the u-boot provided DT, and the hdmi and DRM drivers can be removed and re-inserted at will. The first patch is a straightforward use-after-free, causing a NULL pointer dereference. Moving things around fixes it. The second patch shows that I have no clue about the DRM subsystem whatsoever. I mimicked what my Rockchip systems are doing, and the two warnings disappeared. It can't completely be wrong (famous last words...). The third patch fixes a *very* common issue with regulators (I've fixed at least 3 drivers with a similar issue). I guess the devm subsystem needs to grow a new helper at some point. The last patch finally fixes the issue I was seeing: the HDMI driver hangs when accessing a register with clocks disabled, which they are on module removal. It also fixes my u-boot booting for similar reasons, I guess. I went as far as reaching out for a HDMI cable and verifying that I was getting a working display. Total dedication. Feedback much appreciated. M. Marc Zyngier (4): drm/meson: Free RDMA resources after tearing down DRM drm/meson: Unbind all connectors on module removal drm/meson: dw-hdmi: Register a callback to disable the regulator drm/meson: dw-hdmi: Ensure that clocks are enabled before touching the TOP registers drivers/gpu/drm/meson/meson_drv.c | 12 +++++++----- drivers/gpu/drm/meson/meson_dw_hdmi.c | 13 +++++++++++-- 2 files changed, 18 insertions(+), 7 deletions(-)