From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F303DEEDD for ; Wed, 26 Jun 2024 09:55:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719395746; cv=none; b=tQQw90HTAjyM4N2Fc1RvTVeP6kRyd2Wyg+QXclpXokMlXh3n8vkW6Y4y4XwbYAq6vaFNAczP6Er4zVuIGVLB1g0TRaviB5VkJswlAGwLg/5lq8sN9ozThIq+2oW2smwn/r3mEfN+p3683UUsNWz14WjcATgTYUBiqFNGMEQ8ljs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719395746; c=relaxed/simple; bh=UqxORZFoWrTgtfacpB99r8lUREab2Fbrnsec5IXJypk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hHT5dWsINGoApVhi9c0TRuEJm2qsehcVzPP6IfoXR6Vluxach1ySgRtEvMG8S9rM2jNxMPzUCzNY8zvaG/dSJvSSAolWBt/qton6lDT0LwR0TBM4PeuRMkZ/etVZNgVA3vmaKq2rN0he02ssYdsl+PEoe8FNiymI8LaiIeIn+44= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=e2aRnLWM; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="e2aRnLWM" Received: from [192.168.88.20] (91-158-144-210.elisa-laajakaista.fi [91.158.144.210]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 54C8A73E; Wed, 26 Jun 2024 11:55:19 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1719395719; bh=UqxORZFoWrTgtfacpB99r8lUREab2Fbrnsec5IXJypk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=e2aRnLWMJZzQg5QGhcG3Z8Y4ptYSnu9vHoy8Chj5GttboagVtazoDYP7EsYQjnCtF b9pzjTIo1HyYUO5FyenMZS9ytFHSPxnclnqPf30bwkwlxrTlIyddjx8i24wBs9p6Gh 4mksNBvsEKLFo3uNQnKMMc+l0vRf9+Vnw0HcEOdo= Message-ID: <66ab4206-d1c8-4aad-99a7-c4c316e343a9@ideasonboard.com> Date: Wed, 26 Jun 2024 12:55:39 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/mipi-dsi: Fix devm unregister & detach To: Maxime Ripard Cc: Maarten Lankhorst , Thomas Zimmermann , David Airlie , Daniel Vetter , Laurent Pinchart , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Tomi Valkeinen References: <20240619-dsi-devres-fix-v1-1-a5c59310a52e@ideasonboard.com> <20240626-gabby-ladybug-of-freedom-08e6eb@houat> Content-Language: en-US From: Tomi Valkeinen Autocrypt: addr=tomi.valkeinen@ideasonboard.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 26/06/2024 11:49, Maxime Ripard wrote: > Hi, > > On Wed, Jun 19, 2024 at 12:07:48PM GMT, Tomi Valkeinen wrote: >> From: Tomi Valkeinen >> >> When a bridge driver uses devm_mipi_dsi_device_register_full() or >> devm_mipi_dsi_attach(), the resource management is moved to devres, >> which releases the resource automatically when the bridge driver is >> unbound. >> >> However, if the DSI host goes away first, the host unregistration code >> will automatically detach and unregister any DSI peripherals, without >> notifying the devres about it. So when the bridge driver later is >> unbound, the resources are released a second time, leading to crash. > > That's super surprising. mipi_dsi_device_unregister calls > device_unregister, which calls device_del, which in turn calls > devres_release_all. Hmm, right. > If that doesn't work like that, then it's what needs to be fixed, and > not worked around in the MIPI-DSI bus. Well, something causes a crash for both the device register/unregister case and the attach/detach case, and the call stacks and debug prints showed a double unregister/detach... I need to dig up the board and check again why the devres_release_all() in device_del() doesn't solve this. But I can probably only get back to this in August, so it's perhaps best to ignore this patch for now. However, the attach/detach case is still valid? I see no devres calls in the detach paths. Tomi