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 1815F18E776 for ; Wed, 26 Jun 2024 15:53:45 +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=1719417227; cv=none; b=RLJGNEVjGokBPaFeGfLxuN/5ggGEEOhBNG7YrbO1d7FKZ9c5ki8HVQAA5lJoK6+Oktc7Tboch5kHmWVUzCSh2xVfJ+n2a/w2RYfJSHe2s1wuZigBEv7b8YAH9oC0gI+1qIAdRfmX7Vq+E2UHs1DcQScCzac91LEcKYCdh4Sq/5o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719417227; c=relaxed/simple; bh=1IZh4xEQWMKnAW2kmKyoJwXV0mG3qqnDY0HTqt9psJs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=akvXj5+NzSovjMDd+MTV/kQx7XH/EF4tZMp++ZKaxKllhooiKfeBk+RMjhibIwcR3m5td+ThR2Bbgt2eKrHSgtMVc3cujHWXtIe3+jzLgi8AxVQpFZsX6Go+wrAnVftWu5ZhKn2V8/xolVnVnCzxQ58SMEelIPw0BUlx/frnowQ= ARC-Authentication-Results:i=1; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 26/06/2024 18:07, Maxime Ripard wrote: > On Wed, Jun 26, 2024 at 12:55:39PM GMT, Tomi Valkeinen wrote: >> 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. > > I'm not sure what you mean by the attach/detach case. Do you expect > device resources allocated in attach to be freed when detach run? Ah, never mind, the devres_release_all() would of course deal with that too. However, I just realized/remembered why it crashes. devm_mipi_dsi_device_register_full() and devm_mipi_dsi_attach() are given a device which is used for the devres. This device is probably always the bridge device. So when the bridge device goes away, so do those resources. The mipi_dsi_device_unregister() call deals with a DSI device, which was created in devm_mipi_dsi_device_register_full(). Unregistering that DSI device, which does happen when the DSI host is removed, does not affect the devres of the bridge. So, unloading the DSI host driver causes mipi_dsi_device_unregister() and mipi_dsi_detach() to be called (as part of mipi_dsi_host_unregister()), and unloading the bridge driver causes them to be called again via devres. Tomi