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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 89AC7C352A3 for ; Tue, 11 Feb 2020 08:26:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B2FC20714 for ; Tue, 11 Feb 2020 08:26:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cerno.tech header.i=@cerno.tech header.b="SNpkHcj8"; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="Wml2BvHI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727613AbgBKI0h (ORCPT ); Tue, 11 Feb 2020 03:26:37 -0500 Received: from out5-smtp.messagingengine.com ([66.111.4.29]:59369 "EHLO out5-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727578AbgBKI0h (ORCPT ); Tue, 11 Feb 2020 03:26:37 -0500 Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailout.nyi.internal (Postfix) with ESMTP id 8EE26217FC; Tue, 11 Feb 2020 03:26:33 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute3.internal (MEProxy); Tue, 11 Feb 2020 03:26:33 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cerno.tech; h= date:from:to:cc:subject:message-id:references:mime-version :content-type:in-reply-to; s=fm2; bh=aJFuuqSI2HhjxwelhEtc0Ez5YPf 0KrosR/wT6D9AufM=; b=SNpkHcj8DpzU9/RJO4Dx7NW+qlKd91YZZI1QJXfYz/r mjM6R+IwGn5lZEYn3UCPb5Qju528nBi/21tUOY/rEuvzmK8wnSnACdnG29mYio4t udEXGLB+eBK6xQn7/HDoPcBvcmfsKnO2ckqZcjmiDLx+m296E1rOHeap+Vi/Ry3n NhW4axLlOqzvys1Ul7u7Jq9MYLR2rlc1WTcwDpPJdOIGZzKzhhd1QXn3/0H8p365 8FvXCm0Wd28Tn3ycvgY9T/vMjdZOhf0yXRjjwi5IUT3Me4n23mMvT+qO3qoIizFL LSBnlo+dwPvRen5j179JPXmPAhSs41TvHkXt38svVPQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm2; bh=aJFuuq SI2HhjxwelhEtc0Ez5YPf0KrosR/wT6D9AufM=; b=Wml2BvHI6FDEY4f5OH7zsZ nYzr6x37E8Ztk9Hqxr4Yn2iacvL+KNSKkgrbzvsQkulIZUumb2iL2yLppIwQ2p6b bHs4jnVn2qMCF0CY/JyebH2oWKn1w1HyewQ8WGkPtZ28yZxOWw0J3uOOCdBunMhc xZwSIvsphbzbGHF048UA1zyi6cbAlmVJ3DHMdFGqGaRPfQue2Nyn8eckBihTpYqp eGiAsh+h6QgACz9ELwizRbuEBla1yg4CU6RnmiBcN4xBtfGd1eXfV/Ax5opKnJCJ 02DchwvpAAWoO+fXDSxIn53Vw/9zCmAcqtZad5bgNPKbmtP0u15jmhsjOnYVxkLA == X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedugedriedvgdduudelucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepfffhvffukfhfgggtuggjsehgtderredttddvnecuhfhrohhmpeforgigihhm vgcutfhiphgrrhguuceomhgrgihimhgvsegtvghrnhhordhtvggthheqnecukfhppeeltd drkeelrdeikedrjeeinecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghi lhhfrhhomhepmhgrgihimhgvsegtvghrnhhordhtvggthh X-ME-Proxy: Received: from localhost (lfbn-tou-1-1502-76.w90-89.abo.wanadoo.fr [90.89.68.76]) by mail.messagingengine.com (Postfix) with ESMTPA id C7872328005A; Tue, 11 Feb 2020 03:26:28 -0500 (EST) Date: Tue, 11 Feb 2020 09:26:27 +0100 From: Maxime Ripard To: Samuel Holland Cc: Chen-Yu Tsai , David Airlie , Daniel Vetter , dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 4/4] drm/sun4i: dsi: Remove incorrect use of runtime PM Message-ID: <20200211082627.nolf6npspw2a2rxs@gilmour.lan> References: <20200211072858.30784-1-samuel@sholland.org> <20200211072858.30784-4-samuel@sholland.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="kwpruo3coc5fkck7" Content-Disposition: inline In-Reply-To: <20200211072858.30784-4-samuel@sholland.org> Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org --kwpruo3coc5fkck7 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Hi, On Tue, Feb 11, 2020 at 01:28:58AM -0600, Samuel Holland wrote: > The driver currently uses runtime PM to perform some of the module > initialization and cleanup. This has three problems: > > 1) There is no Kconfig dependency on CONFIG_PM, so if runtime PM is > disabled, the driver will not work at all, since the module will > never be initialized. That's fairly easy to fix. > 2) The driver does not ensure that the device is suspended when > sun6i_dsi_probe() fails or when sun6i_dsi_remove() is called. It > simply disables runtime PM. From the docs of pm_runtime_disable(): > > The device can be either active or suspended after its runtime PM > has been disabled. > > And indeed, the device will likely still be active if sun6i_dsi_probe > fails. For example, if the panel driver is not yet loaded, we have > the following sequence: > > sun6i_dsi_probe() > pm_runtime_enable() > mipi_dsi_host_register() > of_mipi_dsi_device_add(child) > ...device_add()... > __device_attach() > pm_runtime_get_sync(dev->parent) -> Causes resume > bus_for_each_drv() > __device_attach_driver() -> No match for panel > pm_runtime_put(dev->parent) -> Async idle request > component_add() > __component_add() > try_to_bring_up_masters() > try_to_bring_up_master() > sun4i_drv_bind() > component_bind_all() > component_bind() > sun6i_dsi_bind() -> Fails with -EPROBE_DEFER > mipi_dsi_host_unregister() > pm_runtime_disable() > __pm_runtime_disable() > __pm_runtime_barrier() -> Idle request is still pending > cancel_work_sync() -> DSI host is *not* suspended! > > Since the device is not suspended, the clock and regulator are never > disabled. The imbalance causes a WARN at devres free time. That's interesting. I guess this is shown when you have the panel as a module? There's something pretty weird though. The comment in __pm_runtime_disable states that it will "wait for all operations in progress to complete" so at the end of __pm_runtime_disable call, the DSI host will be suspended and we shouldn't have a WARN at all. > 3) The driver relies on being suspended when sun6i_dsi_encoder_enable() > is called. The resume callback has a comment that says: > > Some part of it can only be done once we get a number of > lanes, see sun6i_dsi_inst_init > > And then part of the resume callback only runs if dsi->device is not > NULL (that is, if sun6i_dsi_attach() has been called). However, as > the above call graph shows, the resume callback is guaranteed to be > called before sun6i_dsi_attach(); it is called before child devices > get their drivers attached. Isn't it something that has been changed by your previous patch though? > Therefore, part of the controller initialization will only run if the > device is suspended between the calls to mipi_dsi_host_register() and > component_add() (which ends up calling sun6i_dsi_encoder_enable()). > Again, as shown by the above call graph, this is not the case. It > appears that the controller happens to work because it is still > initialized by the bootloader. We don't have any bootloader support for MIPI-DSI, so no, that's not it. > Because the connector is hardcoded to always be connected, the > device's runtime PM reference is not dropped until system suspend, > when sun4i_drv_drm_sys_suspend() ends up calling > sun6i_dsi_encoder_disable(). However, that is done as a system sleep > PM hook, and at that point the system PM core has already taken > another runtime PM reference, so sun6i_dsi_runtime_suspend() is > not called. Likewise, by the time the PM core releases its reference, > sun4i_drv_drm_sys_resume() has already re-enabled the encoder. > > So after system suspend and resume, we have *still never called* > sun6i_dsi_inst_init(), and now that the rest of the display pipeline > has been reset, the DSI host is unable to communicate with the panel, > causing VBLANK timeouts. Either way, I guess just moving the pm_runtime_enable call to sun6i_dsi_attach will fix this, right? We don't really need to have the DSI controller powered up before that time anyway. > Fix all of these issues by inlining the runtime PM hooks into the > encoder enable/disable functions, which are guaranteed to run after a > panel is attached. This allows sun6i_dsi_inst_init() to be called > unconditionally. Furthermore, this causes the hardware to be turned off > during system suspend and reinitialized on resume, which was not > happening before. That's not something we should do really. We're really lacking any power management, so we should be having more of runtime_pm, not less. Maxime --kwpruo3coc5fkck7 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRcEzekXsqa64kGDp7j7w1vZxhRxQUCXkJlMwAKCRDj7w1vZxhR xYOyAP4i7bV29YYxSgA7p6SjdiD9FeE7lQtf60arSA++ez4MuQD/bU6dsgSPYiwK hMZXytraIuKsW3QZc8GHvc91c2y+dAQ= =fkj2 -----END PGP SIGNATURE----- --kwpruo3coc5fkck7--