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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham 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 58024C4361A for ; Fri, 2 Apr 2021 22:29:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 390CF61183 for ; Fri, 2 Apr 2021 22:29:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236181AbhDBW3p (ORCPT ); Fri, 2 Apr 2021 18:29:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236105AbhDBW3n (ORCPT ); Fri, 2 Apr 2021 18:29:43 -0400 Received: from mail-pj1-x1035.google.com (mail-pj1-x1035.google.com [IPv6:2607:f8b0:4864:20::1035]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6273EC061797 for ; Fri, 2 Apr 2021 15:29:40 -0700 (PDT) Received: by mail-pj1-x1035.google.com with SMTP id ha17so3280327pjb.2 for ; Fri, 02 Apr 2021 15:29:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=Bd7ZOcdLbggTkWq/b11t2tsonPi+tFBvbqHGCQY6R64=; b=Y82Ifp58mbKXik+k+22lEwNmBxDnbi4EdOcUxNE4tS1v8FtKxAXjDKfbiCg1WQ1fwo 9m5VHOYO2zt2rDjV9NpyYNB5AaUcnKTAozlTmgHodqHfwDOnGzuV6pogLfdcuiiaB8C+ GfUTEIrZj4D0dVJE4meMDZmr4ij2391fcpK9o= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Bd7ZOcdLbggTkWq/b11t2tsonPi+tFBvbqHGCQY6R64=; b=tkxBkyOSVH0Qbk2GAuqYyKbJ+x+mM1oB7bAlR/0xrguSgvgRQPDb/ZPO7+KdcnvCZr fYnW4qRsMNEjVIP7oIa4kTgImN9J8+U9SCF0iu9L+pLNkbH1Dw5RIr7gG/fQLqjuZL2L un90vk6H7kPkPyG2VU1lOkUMmd6agcI+XZYS274JtZwB3xrSzgtH/HFnwCrLMq7GQXZu elu+TG4SJYE9Pj7J/9CNnFr4bGr/9USLXfAo2V7gIPmdjZuo1aReGy3OK5jjEyy2nxTp LYyZDvHCt87NhwQJ2kV2F6i/AAjjTMn83T1rRSdk9vxH4oZpwqL5Sl1/1+qTGfcOnZx9 Faqw== X-Gm-Message-State: AOAM531fQIHab5XcA/qasBiS762Scld8sM03NBQMAGzpp8+qp4b3tnLI mqXLBoMmgD3K+9X6TGysmKbymw== X-Google-Smtp-Source: ABdhPJxIVU3dtJ6L+VxCnlaevQ2t7j0kZEkmzIZuSwfT1L7CjV9b4QC3Izww+hVdZMWB+Q+O6j29oA== X-Received: by 2002:a17:902:e051:b029:e7:37d9:f32e with SMTP id x17-20020a170902e051b02900e737d9f32emr14488918plx.78.1617402579937; Fri, 02 Apr 2021 15:29:39 -0700 (PDT) Received: from tictac2.mtv.corp.google.com ([2620:15c:202:201:6c58:fab2:c5e2:f2d7]) by smtp.gmail.com with ESMTPSA id t16sm9233094pfc.204.2021.04.02.15.29.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Apr 2021 15:29:39 -0700 (PDT) From: Douglas Anderson To: Andrzej Hajda , Neil Armstrong , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Sam Ravnborg Cc: Linus W , Bjorn Andersson , robdclark@chromium.org, Stephen Boyd , Steev Klimaszewski , Maarten Lankhorst , linux-arm-msm@vger.kernel.org, Stanislav Lisovskiy , Douglas Anderson , Daniel Vetter , David Airlie , Thierry Reding , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 12/12] drm/panel: panel-simple: Use runtime pm to avoid excessive unprepare / prepare Date: Fri, 2 Apr 2021 15:28:46 -0700 Message-Id: <20210402152701.v3.12.I9e8bd33b49c496745bfac58ea9ab418bd3b6f5ce@changeid> X-Mailer: git-send-email 2.31.0.208.g409f899ff0-goog In-Reply-To: <20210402222846.2461042-1-dianders@chromium.org> References: <20210402222846.2461042-1-dianders@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Unpreparing and re-preparing a panel can be a really heavy operation. Panels datasheets often specify something on the order of 500ms as the delay you should insert after turning off the panel before turning it on again. In addition, turning on a panel can have delays on the order of 100ms - 200ms before the panel will assert HPD (AKA "panel ready"). The above means that we should avoid turning a panel off if we're going to turn it on again shortly. The above becomes a problem when we want to read the EDID of a panel. The way that ordering works is that userspace wants to read the EDID of the panel _before_ fully enabling it so that it can set the initial mode correctly. However, we can't read the EDID until we power it up. This leads to code that does this dance (like ps8640_bridge_get_edid()): 1. When userspace requests EDID / the panel modes (through an ioctl), we power on the panel just enough to read the EDID and then power it off. 2. Userspace then turns the panel on. There's likely not much time between step #1 and #2 and so we want to avoid powering the panel off and on again between those two steps. Let's use Runtime PM to help us. We'll move the existing prepare() and unprepare() to be runtime resume() and runtime suspend(). Now when we want to prepare() or unprepare() we just increment or decrement the refcount. We'll default to a 1 second autosuspend delay which seems sane given the typical delays we see for panels. A few notes: - It seems the existing unprepare() and prepare() are defined to be no-ops if called extra times. We'll preserve that behavior. - This is a slight change in the ABI of simple panel. If something was absolutely relying on the unprepare() to happen instantly that simply won't be the case anymore. I'm not aware of anyone relying on that behavior, but if there is someone then we'll need to figure out how to enable (or disable) this new delayed behavior selectively. - In order for this to work we now have a hard dependency on "PM". From memory this is a legit thing to assume these days and we don't have to find some fallback to keep working if someone wants to build their system without "PM". Signed-off-by: Douglas Anderson --- (no changes since v1) drivers/gpu/drm/panel/Kconfig | 1 + drivers/gpu/drm/panel/panel-simple.c | 93 +++++++++++++++++++++------- 2 files changed, 73 insertions(+), 21 deletions(-) diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig index 4894913936e9..ef87d92cdf49 100644 --- a/drivers/gpu/drm/panel/Kconfig +++ b/drivers/gpu/drm/panel/Kconfig @@ -80,6 +80,7 @@ config DRM_PANEL_SIMPLE tristate "support for simple panels" depends on OF depends on BACKLIGHT_CLASS_DEVICE + depends on PM select VIDEOMODE_HELPERS help DRM panel driver for dumb panels that need at most a regulator and diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c index be312b5c04dd..6b22872b3281 100644 --- a/drivers/gpu/drm/panel/panel-simple.c +++ b/drivers/gpu/drm/panel/panel-simple.c @@ -27,6 +27,7 @@ #include #include #include +#include #include #include