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[209.85.219.174]) by smtp.gmail.com with ESMTPSA id j13sm4647410qth.57.2021.04.23.09.53.20 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 23 Apr 2021 09:53:20 -0700 (PDT) Received: by mail-yb1-f174.google.com with SMTP id g38so56342349ybi.12 for ; Fri, 23 Apr 2021 09:53:20 -0700 (PDT) X-Received: by 2002:a25:6088:: with SMTP id u130mr7214627ybb.257.1619196429157; Fri, 23 Apr 2021 09:47:09 -0700 (PDT) MIME-Version: 1.0 References: <20210416223950.3586967-1-dianders@chromium.org> <20210416153909.v4.27.I502f2a92ddd36c3d28d014dd75e170c2d405a0a5@changeid> In-Reply-To: <20210416153909.v4.27.I502f2a92ddd36c3d28d014dd75e170c2d405a0a5@changeid> From: Doug Anderson Date: Fri, 23 Apr 2021 09:46:57 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v4 27/27] drm/panel: panel-simple: Prepare/unprepare are refcounted, not forced To: Andrzej Hajda , Neil Armstrong , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Sam Ravnborg , Wolfram Sang Cc: Stephen Boyd , Rob Clark , Maarten Lankhorst , Stanislav Lisovskiy , Steev Klimaszewski , Bjorn Andersson , linux-arm-msm , Linus W , Daniel Vetter , David Airlie , Thierry Reding , dri-devel , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Hi, On Fri, Apr 16, 2021 at 3:41 PM Douglas Anderson wrote: > > Historically simple-panel had code to make sure that if prepare() was > called on an already-prepared panel that it was a no-op. Similarly if > unprepare() was called on an already-unprepared panel it was also a > no-op. Essentially it means that these functions always "forced" the > value to be whatever the caller wanted it to be. You can see that the > forcing behavior dates back at least as far as 2014 by looking at > commit 613a633e7a56 ("drm/panel: simple: Add proper definition for > prepare and unprepare"). > > Apparently the code supporting the historical behavior may not be > needed [1] and prepare() / unprepare() are supposed to be > balanced. Let's try removing it and see if anyone breaks! If they do > then we can have a debate about whether we should change that code or > revert this patch. :-) If nobody breaks then we've nicely saved a few > lines of code and some complexity. > > [1] https://lore.kernel.org/r/YHePsQgqOau1V5lD@pendragon.ideasonboard.com > > Suggested-by: Laurent Pinchart > Signed-off-by: Douglas Anderson > --- > > (no changes since v1) > > drivers/gpu/drm/panel/panel-simple.c | 14 -------------- > 1 file changed, 14 deletions(-) So it turns out that when looking at panel_simple_remove() I already found a case that's not necessarily refcounting. There I see drm_panel_unprepare() just simply hardcoded, but (as I understand it) there's no reason to believe that the panel has been prepared at remove() time. Yes, I could fix panel_simple_remove() but instead, for now, I think I'm going to drop this patch from the series. If someone wants to pick it up then I certainly won't object, but for now keeping the way things are seems the best way to keep from getting shouted at. -Doug 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=-13.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 6FC06C433ED for ; Fri, 23 Apr 2021 16:47:14 +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 187D161476 for ; Fri, 23 Apr 2021 16:47:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 187D161476 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.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 503506EC06; Fri, 23 Apr 2021 16:47:13 +0000 (UTC) Received: from mail-qk1-x730.google.com (mail-qk1-x730.google.com [IPv6:2607:f8b0:4864:20::730]) by gabe.freedesktop.org (Postfix) with ESMTPS id B19696EC06 for ; Fri, 23 Apr 2021 16:47:11 +0000 (UTC) Received: by mail-qk1-x730.google.com with SMTP id x11so50159830qkp.11 for ; Fri, 23 Apr 2021 09:47:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=DND1iGGPjngmHTVlV+c4Q20wbAG71cect3ZWcNu/fqM=; b=HEvzLaXsM1O3YDF7kXj6cV9W3z/mj/YaZRnHFlBZ2rpsku/yo45gm9QY1TDQ+b0Q2Q 4QmACTulVrObY8AyQsXioItz4TGmlCVL/xhIo2hpFyVGQOkbET4Dy+zwn72r3lYZUfpH +pv1WLGIP5dCOKj6dRBy4N34rssSE/rrgyn1c= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=DND1iGGPjngmHTVlV+c4Q20wbAG71cect3ZWcNu/fqM=; b=rVOWv3q2llkZfuKdBMziKY3clwLuO7J+6VUhV/Qx/Un6Ci/ZqZM7nyPCoDm5fg68Cb ysXGey2KSSSRj8M5q/bdLSClVprKcHaBTXIdEek3Oc5CL5oPIXN14MBkgNOefW27Fapd jFYwhZlCJUDfwneq6PgqtdsD4Sus/aOvYIfX+4Bpm9v8tY6NUo4P2Q6rjbWY6nNSjXB+ UPnxSVng4eLbBIXRqFElloVp1PM4ojVL9I574bbqIn1g7N22Pnya77vQkUwKLEShKpJt VEhaUMUDzUnIFwCBztExOTmAh89241RGxe7nD3jtziH4dRWULuOkEXbR1EJ2IjqHaCI2 7kUw== X-Gm-Message-State: AOAM532IYSbXDd82qOOvDnBUnbcXJCQuZQ56zg7+ZG7LvHFggEX8qWGT 4gLCpsMBOYNAxDHZwR3Lhbxel1MHo4hdow== X-Google-Smtp-Source: ABdhPJw71DlWhcPVVs8K4+4Td0/+C90pPgEqv5eQNwLCW9nz0yltgtoPCQ8i9Or5NLh1ygFA050ZKA== X-Received: by 2002:a37:906:: with SMTP id 6mr4961565qkj.234.1619196430302; Fri, 23 Apr 2021 09:47:10 -0700 (PDT) Received: from mail-yb1-f175.google.com (mail-yb1-f175.google.com. [209.85.219.175]) by smtp.gmail.com with ESMTPSA id g185sm4733821qkf.62.2021.04.23.09.47.09 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 23 Apr 2021 09:47:09 -0700 (PDT) Received: by mail-yb1-f175.google.com with SMTP id g38so56321464ybi.12 for ; Fri, 23 Apr 2021 09:47:09 -0700 (PDT) X-Received: by 2002:a25:6088:: with SMTP id u130mr7214627ybb.257.1619196429157; Fri, 23 Apr 2021 09:47:09 -0700 (PDT) MIME-Version: 1.0 References: <20210416223950.3586967-1-dianders@chromium.org> <20210416153909.v4.27.I502f2a92ddd36c3d28d014dd75e170c2d405a0a5@changeid> In-Reply-To: <20210416153909.v4.27.I502f2a92ddd36c3d28d014dd75e170c2d405a0a5@changeid> From: Doug Anderson Date: Fri, 23 Apr 2021 09:46:57 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v4 27/27] drm/panel: panel-simple: Prepare/unprepare are refcounted, not forced To: Andrzej Hajda , Neil Armstrong , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Sam Ravnborg , Wolfram Sang 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: Rob Clark , David Airlie , linux-arm-msm , LKML , Steev Klimaszewski , Bjorn Andersson , Stanislav Lisovskiy , Thierry Reding , dri-devel , Stephen Boyd Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi, On Fri, Apr 16, 2021 at 3:41 PM Douglas Anderson wrote: > > Historically simple-panel had code to make sure that if prepare() was > called on an already-prepared panel that it was a no-op. Similarly if > unprepare() was called on an already-unprepared panel it was also a > no-op. Essentially it means that these functions always "forced" the > value to be whatever the caller wanted it to be. You can see that the > forcing behavior dates back at least as far as 2014 by looking at > commit 613a633e7a56 ("drm/panel: simple: Add proper definition for > prepare and unprepare"). > > Apparently the code supporting the historical behavior may not be > needed [1] and prepare() / unprepare() are supposed to be > balanced. Let's try removing it and see if anyone breaks! If they do > then we can have a debate about whether we should change that code or > revert this patch. :-) If nobody breaks then we've nicely saved a few > lines of code and some complexity. > > [1] https://lore.kernel.org/r/YHePsQgqOau1V5lD@pendragon.ideasonboard.com > > Suggested-by: Laurent Pinchart > Signed-off-by: Douglas Anderson > --- > > (no changes since v1) > > drivers/gpu/drm/panel/panel-simple.c | 14 -------------- > 1 file changed, 14 deletions(-) So it turns out that when looking at panel_simple_remove() I already found a case that's not necessarily refcounting. There I see drm_panel_unprepare() just simply hardcoded, but (as I understand it) there's no reason to believe that the panel has been prepared at remove() time. Yes, I could fix panel_simple_remove() but instead, for now, I think I'm going to drop this patch from the series. If someone wants to pick it up then I certainly won't object, but for now keeping the way things are seems the best way to keep from getting shouted at. -Doug _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel