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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 20F5EC4332F for ; Tue, 5 Apr 2022 09:24:16 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id F335E10E5E4; Tue, 5 Apr 2022 09:24:14 +0000 (UTC) Received: from mail-oa1-x36.google.com (mail-oa1-x36.google.com [IPv6:2001:4860:4864:20::36]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0EC9710E5E4 for ; Tue, 5 Apr 2022 09:24:14 +0000 (UTC) Received: by mail-oa1-x36.google.com with SMTP id 586e51a60fabf-d39f741ba0so13709174fac.13 for ; Tue, 05 Apr 2022 02:24:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=8lxRDcdRQ5w1Q2jCVMX+xvmqdaWkgW8uu97T4fHS8x4=; b=E7utYSEQMMriUu3qMfwO6HZ+45PXmrgq9OM+1s//K6zpWGIFlVpV9kYS7Tmb7YhWlD NkBhw6QH+PA6UFcYFNsQg+mT3l+j/b3yiMV0z5OgJqRnaezfoO6hggNnTdTjEqHTI0zV 2wAOmzOy1RGhDB2wL/45uzYgskBCHCu8iM08c= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=8lxRDcdRQ5w1Q2jCVMX+xvmqdaWkgW8uu97T4fHS8x4=; b=Zrq25AG6riRWiC/s1Hz/I5uFgu6Zi8MO1LHe0jNYNbZ5d03FC+U/zGb+OMOZwffmjJ 2VS4OlIo4PYY7CEJuCdBubpNnndxY6IjgrVBoe11/eCMyJdWReh4txEzDXQm2GYwOTUo jwak57C3tFuT0Xf9RM0NiS/aay8NmyjEeg27lQ17XdYmI8KKptzD+iVhKr4WyDqeTF4h E/l4wAk50IH0ACj4bzbYvlCjoAsCdeEe8np5KgnBTXqtr1l2b6YAFADYGjxc5wHOib8F b2N1P62qBGt1wUIWPjBAppAp6hr75LI2QJKtqbcPTyV++aGzhrDLyzGndqyZs7jdRRfh DRww== X-Gm-Message-State: AOAM530IEWt0ivAPnro+pq6BViBZ+b/rBN7d8uB6efm655rvdexra/yU 0RU+C+tUTBvgsRvYqBTXh4a/EeRZ6+It3uMbM2cUdg== X-Google-Smtp-Source: ABdhPJyzL3zZzTHLZEn2qSsiB+5Zic+Cf7QVJB23RMBqDKq8SPt6RfSyxRU86S94alZw81SeHDZ6ususLht4Jn/mafs= X-Received: by 2002:a05:6870:eaa5:b0:da:b3f:2b45 with SMTP id s37-20020a056870eaa500b000da0b3f2b45mr1132529oap.228.1649150653253; Tue, 05 Apr 2022 02:24:13 -0700 (PDT) MIME-Version: 1.0 References: <20220208210824.2238981-1-daniel.vetter@ffwll.ch> <20220208210824.2238981-19-daniel.vetter@ffwll.ch> <4ae20b63-f452-fdb4-ced6-d4968a8d69f0@redhat.com> <408ffe9b-f09f-dc7e-7f5e-a93b311a06fa@redhat.com> In-Reply-To: <408ffe9b-f09f-dc7e-7f5e-a93b311a06fa@redhat.com> From: Daniel Vetter Date: Tue, 5 Apr 2022 11:24:01 +0200 Message-ID: Subject: Re: [PATCH v2 18/19] Revert "fbdev: Prevent probing generic drivers if a FB is already registered" To: Javier Martinez Canillas Content-Type: text/plain; charset="UTF-8" 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: linux-fbdev@vger.kernel.org, Intel Graphics Development , LKML , DRI Development , Hans de Goede , Peter Jones , Thomas Zimmermann , Ilya Trukhanov , Daniel Vetter Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, 5 Apr 2022 at 11:19, Javier Martinez Canillas wrote: > > Hello Daniel, > > On 4/5/22 10:40, Daniel Vetter wrote: > > On Tue, Apr 05, 2022 at 10:36:35AM +0200, Daniel Vetter wrote: > >> On Wed, Feb 09, 2022 at 01:19:26AM +0100, Javier Martinez Canillas wrote: > >>> On 2/8/22 22:08, Daniel Vetter wrote: > >>>> This reverts commit fb561bf9abde49f7e00fdbf9ed2ccf2d86cac8ee. > >>>> > >>>> With > >>>> > >>>> commit 27599aacbaefcbf2af7b06b0029459bbf682000d > >>>> Author: Thomas Zimmermann > >>>> Date: Tue Jan 25 10:12:18 2022 +0100 > >>>> > >>>> fbdev: Hot-unplug firmware fb devices on forced removal > >>>> > >>>> this should be fixed properly and we can remove this somewhat hackish > >>>> check here (e.g. this won't catch drm drivers if fbdev emulation isn't > >>>> enabled). > >>>> > >>> > >>> Unfortunately this hack can't be reverted yet. Thomas' patch solves the issue > >>> of platform devices matched with fbdev drivers to be properly unregistered if > >>> a DRM driver attempts to remove all the conflicting framebuffers. > >>> > >>> But the problem that fb561bf9abde ("fbdev: Prevent probing generic drivers if > >>> a FB is already registered") worked around is different. It happens when the > >>> DRM driver is probed before the {efi,simple}fb and other fbdev drivers, the > >>> kicking out of conflicting framebuffers already happened and these drivers > >>> will be allowed to probe even when a DRM driver is already present. > >>> > >>> We need a clearer way to prevent it, but can't revert fb561bf9abde until that. > >> > >> Yeah that entire area is a mess still, ideally we'd have something else > >> creating the platform devices, and efifb/offb and all these would just > >> bind against them. > >> > >> Hm one idea that just crossed my mind: Could we have a flag in fb_info for > >> fw drivers, and check this in framebuffer_register? Then at least all the > >> logic would be in the fbdev core. > > > > I can't answer right away since I've since forgotten this part of the code > and will require to do a detailed read to refresh my memory. > > I'll answer later but preferred to mention the other question ASAP. > > > Ok coffee just kicked in, how exactly does your scenario work? > > > > This code I'm reverting here is in the platform_dev->probe function. > > Thomas' patch removes the platform_dev. How exactly can you still probe > > against a platform dev if that platform dev is gone? > > > > Because the platform was not even registered by the time the DRM driver > probed and all the devices for the conflicting drivers were unregistered. > > > Iow, now that I reponder your case after a few weeks I'm no longer sure > > things work like you claim. > > > > This is how I think that work, please let me know if you see something > wrong in my logic: > > 1) A PCI device of OF device is registered for the GPU, this attempt to > match a registered driver but no driver was registered that match yet. > > 2) The efifb driver is built-in, will be initialized according to the link > order of the objects under drivers/video and the fbdev driver is registered. > > There is no platform device or PCI/OF device registered that matches. > > 3) The DRM driver is built-in, will be initialized according to the link > order of the objects under drivers/gpu and the DRM driver is registered. > > This matches the device registered in (1) and the DRM driver probes. > > 4) The DRM driver .probe kicks out any conflicting DRM drivers and pdev > before registering the DRM device. > > There are no conflicting drivers or platform device at this point. > > 5) Latter at some point the drivers/firmware/sysfb.c init function is > executed, and this registers a platform device for the generic fb. > > This device matches the efifb driver registered in (2) and the fbdev > driver probes. > > Since that happens *after* the DRM driver already matched, probed > and registered the DRM device, that is a bug and what the reverted > patch worked around. > > So we need to prevent (5) if (1) and (3) already happened. Having a flag > set in the fbdev core somewhere when remove_conflicting_framebuffers() > is called could be a solution indeed. > > That is, the fbdev core needs to know that a DRM driver already probed > and make register_framebuffer() fail if info->flag & FBINFO_MISC_FIRMWARE > > I can attempt to write a patch for that. Ah yeah that could be an issue. I think the right fix is to replace the platform dev unregister with a sysfb_unregister() function in sysfb.c, which is synced with a common lock with the sysfb_init function and a small boolean. I think I can type that up quickly for v3. -Daniel > > -- > Best regards, > > Javier Martinez Canillas > Linux Engineering > Red Hat > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id B0537C433F5 for ; Tue, 5 Apr 2022 09:24:15 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 034A710EA26; Tue, 5 Apr 2022 09:24:15 +0000 (UTC) Received: from mail-oa1-x34.google.com (mail-oa1-x34.google.com [IPv6:2001:4860:4864:20::34]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2FCDA10EA26 for ; Tue, 5 Apr 2022 09:24:14 +0000 (UTC) Received: by mail-oa1-x34.google.com with SMTP id 586e51a60fabf-deb9295679so13752397fac.6 for ; Tue, 05 Apr 2022 02:24:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=8lxRDcdRQ5w1Q2jCVMX+xvmqdaWkgW8uu97T4fHS8x4=; b=E7utYSEQMMriUu3qMfwO6HZ+45PXmrgq9OM+1s//K6zpWGIFlVpV9kYS7Tmb7YhWlD NkBhw6QH+PA6UFcYFNsQg+mT3l+j/b3yiMV0z5OgJqRnaezfoO6hggNnTdTjEqHTI0zV 2wAOmzOy1RGhDB2wL/45uzYgskBCHCu8iM08c= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=8lxRDcdRQ5w1Q2jCVMX+xvmqdaWkgW8uu97T4fHS8x4=; b=qCJNtv4iIqENESmEFXecdE8fPvIa3D7hURecZJG3K2HCugXNIZFAntzs+G9SrReLVG N/UJ+Fr/PsRVMIvRRTFYDBLNoPYeDhLBqdGdKOBekAhhpeptOL2SoeDsDnO9/CQtZtwV GPeAWqO+HKTVuZpJBdrT2W/hAlRv/K91R8lUq5alsP/GyfMj38sPSk0JwXEqZANbIcrS bAbKJmS1N6yKz85F3yeXqJ2ZebGZ7wK6z6YfQMi4FpsgFWretny5nOYmJuK/bZcIbts7 nfG30QXBbQB4ujsLc0rBsIoYrDdUcoKF3xzvOc9CMIxjupaMRjORE602vpRGdnywQN1K KnQw== X-Gm-Message-State: AOAM5301+OHotfoGs/UnsRNepxsZGGQJZnTJj8Z6WZkLXFpPD0SlsWcZ iaDRjXvI8eKlNvEIolRrFL5wQkC5SVxhrBsBkFTg5g== X-Google-Smtp-Source: ABdhPJyzL3zZzTHLZEn2qSsiB+5Zic+Cf7QVJB23RMBqDKq8SPt6RfSyxRU86S94alZw81SeHDZ6ususLht4Jn/mafs= X-Received: by 2002:a05:6870:eaa5:b0:da:b3f:2b45 with SMTP id s37-20020a056870eaa500b000da0b3f2b45mr1132529oap.228.1649150653253; Tue, 05 Apr 2022 02:24:13 -0700 (PDT) MIME-Version: 1.0 References: <20220208210824.2238981-1-daniel.vetter@ffwll.ch> <20220208210824.2238981-19-daniel.vetter@ffwll.ch> <4ae20b63-f452-fdb4-ced6-d4968a8d69f0@redhat.com> <408ffe9b-f09f-dc7e-7f5e-a93b311a06fa@redhat.com> In-Reply-To: <408ffe9b-f09f-dc7e-7f5e-a93b311a06fa@redhat.com> From: Daniel Vetter Date: Tue, 5 Apr 2022 11:24:01 +0200 Message-ID: To: Javier Martinez Canillas Content-Type: text/plain; charset="UTF-8" Subject: Re: [Intel-gfx] [PATCH v2 18/19] Revert "fbdev: Prevent probing generic drivers if a FB is already registered" X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-fbdev@vger.kernel.org, Intel Graphics Development , LKML , DRI Development , Peter Jones , Thomas Zimmermann , Ilya Trukhanov , Daniel Vetter , Zack Rusin Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Tue, 5 Apr 2022 at 11:19, Javier Martinez Canillas wrote: > > Hello Daniel, > > On 4/5/22 10:40, Daniel Vetter wrote: > > On Tue, Apr 05, 2022 at 10:36:35AM +0200, Daniel Vetter wrote: > >> On Wed, Feb 09, 2022 at 01:19:26AM +0100, Javier Martinez Canillas wrote: > >>> On 2/8/22 22:08, Daniel Vetter wrote: > >>>> This reverts commit fb561bf9abde49f7e00fdbf9ed2ccf2d86cac8ee. > >>>> > >>>> With > >>>> > >>>> commit 27599aacbaefcbf2af7b06b0029459bbf682000d > >>>> Author: Thomas Zimmermann > >>>> Date: Tue Jan 25 10:12:18 2022 +0100 > >>>> > >>>> fbdev: Hot-unplug firmware fb devices on forced removal > >>>> > >>>> this should be fixed properly and we can remove this somewhat hackish > >>>> check here (e.g. this won't catch drm drivers if fbdev emulation isn't > >>>> enabled). > >>>> > >>> > >>> Unfortunately this hack can't be reverted yet. Thomas' patch solves the issue > >>> of platform devices matched with fbdev drivers to be properly unregistered if > >>> a DRM driver attempts to remove all the conflicting framebuffers. > >>> > >>> But the problem that fb561bf9abde ("fbdev: Prevent probing generic drivers if > >>> a FB is already registered") worked around is different. It happens when the > >>> DRM driver is probed before the {efi,simple}fb and other fbdev drivers, the > >>> kicking out of conflicting framebuffers already happened and these drivers > >>> will be allowed to probe even when a DRM driver is already present. > >>> > >>> We need a clearer way to prevent it, but can't revert fb561bf9abde until that. > >> > >> Yeah that entire area is a mess still, ideally we'd have something else > >> creating the platform devices, and efifb/offb and all these would just > >> bind against them. > >> > >> Hm one idea that just crossed my mind: Could we have a flag in fb_info for > >> fw drivers, and check this in framebuffer_register? Then at least all the > >> logic would be in the fbdev core. > > > > I can't answer right away since I've since forgotten this part of the code > and will require to do a detailed read to refresh my memory. > > I'll answer later but preferred to mention the other question ASAP. > > > Ok coffee just kicked in, how exactly does your scenario work? > > > > This code I'm reverting here is in the platform_dev->probe function. > > Thomas' patch removes the platform_dev. How exactly can you still probe > > against a platform dev if that platform dev is gone? > > > > Because the platform was not even registered by the time the DRM driver > probed and all the devices for the conflicting drivers were unregistered. > > > Iow, now that I reponder your case after a few weeks I'm no longer sure > > things work like you claim. > > > > This is how I think that work, please let me know if you see something > wrong in my logic: > > 1) A PCI device of OF device is registered for the GPU, this attempt to > match a registered driver but no driver was registered that match yet. > > 2) The efifb driver is built-in, will be initialized according to the link > order of the objects under drivers/video and the fbdev driver is registered. > > There is no platform device or PCI/OF device registered that matches. > > 3) The DRM driver is built-in, will be initialized according to the link > order of the objects under drivers/gpu and the DRM driver is registered. > > This matches the device registered in (1) and the DRM driver probes. > > 4) The DRM driver .probe kicks out any conflicting DRM drivers and pdev > before registering the DRM device. > > There are no conflicting drivers or platform device at this point. > > 5) Latter at some point the drivers/firmware/sysfb.c init function is > executed, and this registers a platform device for the generic fb. > > This device matches the efifb driver registered in (2) and the fbdev > driver probes. > > Since that happens *after* the DRM driver already matched, probed > and registered the DRM device, that is a bug and what the reverted > patch worked around. > > So we need to prevent (5) if (1) and (3) already happened. Having a flag > set in the fbdev core somewhere when remove_conflicting_framebuffers() > is called could be a solution indeed. > > That is, the fbdev core needs to know that a DRM driver already probed > and make register_framebuffer() fail if info->flag & FBINFO_MISC_FIRMWARE > > I can attempt to write a patch for that. Ah yeah that could be an issue. I think the right fix is to replace the platform dev unregister with a sysfb_unregister() function in sysfb.c, which is synced with a common lock with the sysfb_init function and a small boolean. I think I can type that up quickly for v3. -Daniel > > -- > Best regards, > > Javier Martinez Canillas > Linux Engineering > Red Hat > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch 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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27E02C4332F for ; Tue, 5 Apr 2022 14:40:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349350AbiDEOgr (ORCPT ); Tue, 5 Apr 2022 10:36:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239532AbiDEJfV (ORCPT ); Tue, 5 Apr 2022 05:35:21 -0400 Received: from mail-oa1-x2e.google.com (mail-oa1-x2e.google.com [IPv6:2001:4860:4864:20::2e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 26ABA88B27 for ; Tue, 5 Apr 2022 02:24:13 -0700 (PDT) Received: by mail-oa1-x2e.google.com with SMTP id 586e51a60fabf-df22f50e0cso13785054fac.3 for ; Tue, 05 Apr 2022 02:24:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=8lxRDcdRQ5w1Q2jCVMX+xvmqdaWkgW8uu97T4fHS8x4=; b=E7utYSEQMMriUu3qMfwO6HZ+45PXmrgq9OM+1s//K6zpWGIFlVpV9kYS7Tmb7YhWlD NkBhw6QH+PA6UFcYFNsQg+mT3l+j/b3yiMV0z5OgJqRnaezfoO6hggNnTdTjEqHTI0zV 2wAOmzOy1RGhDB2wL/45uzYgskBCHCu8iM08c= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=8lxRDcdRQ5w1Q2jCVMX+xvmqdaWkgW8uu97T4fHS8x4=; b=W313WGgMHesyXX2zRaa1FBp5pohdc0eBNcctyIKBeONwep+uN69NXiRsPjZdUvmrhw F6ZcI7lDl5pxit8X35qoPo1Ls0bPMFqrnclKmbAT9bANCi36Cjxd2rJmLj3CRHlfz+Fs 5oCZp6GCq1pUupa3dUX4GP1jMDBntQLHgFnGFsS0+4cQUkClUFjxGHrNtBNA05GeNg57 weJntVWuzzf0SFfXntxpUJhXrBaNxAh7xhu1s0LELVctDoepAqfKeqQIUw3zFTIdGz/y t+0xzBIlUeC0fjSkCbjnT7wlx0znDjh7SRQJREcrfxRfqhwV+BPxfFoEsx+HWZEE81lM qjmQ== X-Gm-Message-State: AOAM531JWrfMCpFhdri0ECiwq/RGxyAf6EAAHxvGKBgqXWXgJ1WPWMjI gqRK/4nYCWTLZmfSoc5/K2t5Ycdi5jYm3/h7jRfGPw== X-Google-Smtp-Source: ABdhPJyzL3zZzTHLZEn2qSsiB+5Zic+Cf7QVJB23RMBqDKq8SPt6RfSyxRU86S94alZw81SeHDZ6ususLht4Jn/mafs= X-Received: by 2002:a05:6870:eaa5:b0:da:b3f:2b45 with SMTP id s37-20020a056870eaa500b000da0b3f2b45mr1132529oap.228.1649150653253; Tue, 05 Apr 2022 02:24:13 -0700 (PDT) MIME-Version: 1.0 References: <20220208210824.2238981-1-daniel.vetter@ffwll.ch> <20220208210824.2238981-19-daniel.vetter@ffwll.ch> <4ae20b63-f452-fdb4-ced6-d4968a8d69f0@redhat.com> <408ffe9b-f09f-dc7e-7f5e-a93b311a06fa@redhat.com> In-Reply-To: <408ffe9b-f09f-dc7e-7f5e-a93b311a06fa@redhat.com> From: Daniel Vetter Date: Tue, 5 Apr 2022 11:24:01 +0200 Message-ID: Subject: Re: [PATCH v2 18/19] Revert "fbdev: Prevent probing generic drivers if a FB is already registered" To: Javier Martinez Canillas Cc: DRI Development , Intel Graphics Development , linux-fbdev@vger.kernel.org, LKML , Thomas Zimmermann , Zack Rusin , Hans de Goede , Ilya Trukhanov , Daniel Vetter , Peter Jones Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 5 Apr 2022 at 11:19, Javier Martinez Canillas wrote: > > Hello Daniel, > > On 4/5/22 10:40, Daniel Vetter wrote: > > On Tue, Apr 05, 2022 at 10:36:35AM +0200, Daniel Vetter wrote: > >> On Wed, Feb 09, 2022 at 01:19:26AM +0100, Javier Martinez Canillas wrote: > >>> On 2/8/22 22:08, Daniel Vetter wrote: > >>>> This reverts commit fb561bf9abde49f7e00fdbf9ed2ccf2d86cac8ee. > >>>> > >>>> With > >>>> > >>>> commit 27599aacbaefcbf2af7b06b0029459bbf682000d > >>>> Author: Thomas Zimmermann > >>>> Date: Tue Jan 25 10:12:18 2022 +0100 > >>>> > >>>> fbdev: Hot-unplug firmware fb devices on forced removal > >>>> > >>>> this should be fixed properly and we can remove this somewhat hackish > >>>> check here (e.g. this won't catch drm drivers if fbdev emulation isn't > >>>> enabled). > >>>> > >>> > >>> Unfortunately this hack can't be reverted yet. Thomas' patch solves the issue > >>> of platform devices matched with fbdev drivers to be properly unregistered if > >>> a DRM driver attempts to remove all the conflicting framebuffers. > >>> > >>> But the problem that fb561bf9abde ("fbdev: Prevent probing generic drivers if > >>> a FB is already registered") worked around is different. It happens when the > >>> DRM driver is probed before the {efi,simple}fb and other fbdev drivers, the > >>> kicking out of conflicting framebuffers already happened and these drivers > >>> will be allowed to probe even when a DRM driver is already present. > >>> > >>> We need a clearer way to prevent it, but can't revert fb561bf9abde until that. > >> > >> Yeah that entire area is a mess still, ideally we'd have something else > >> creating the platform devices, and efifb/offb and all these would just > >> bind against them. > >> > >> Hm one idea that just crossed my mind: Could we have a flag in fb_info for > >> fw drivers, and check this in framebuffer_register? Then at least all the > >> logic would be in the fbdev core. > > > > I can't answer right away since I've since forgotten this part of the code > and will require to do a detailed read to refresh my memory. > > I'll answer later but preferred to mention the other question ASAP. > > > Ok coffee just kicked in, how exactly does your scenario work? > > > > This code I'm reverting here is in the platform_dev->probe function. > > Thomas' patch removes the platform_dev. How exactly can you still probe > > against a platform dev if that platform dev is gone? > > > > Because the platform was not even registered by the time the DRM driver > probed and all the devices for the conflicting drivers were unregistered. > > > Iow, now that I reponder your case after a few weeks I'm no longer sure > > things work like you claim. > > > > This is how I think that work, please let me know if you see something > wrong in my logic: > > 1) A PCI device of OF device is registered for the GPU, this attempt to > match a registered driver but no driver was registered that match yet. > > 2) The efifb driver is built-in, will be initialized according to the link > order of the objects under drivers/video and the fbdev driver is registered. > > There is no platform device or PCI/OF device registered that matches. > > 3) The DRM driver is built-in, will be initialized according to the link > order of the objects under drivers/gpu and the DRM driver is registered. > > This matches the device registered in (1) and the DRM driver probes. > > 4) The DRM driver .probe kicks out any conflicting DRM drivers and pdev > before registering the DRM device. > > There are no conflicting drivers or platform device at this point. > > 5) Latter at some point the drivers/firmware/sysfb.c init function is > executed, and this registers a platform device for the generic fb. > > This device matches the efifb driver registered in (2) and the fbdev > driver probes. > > Since that happens *after* the DRM driver already matched, probed > and registered the DRM device, that is a bug and what the reverted > patch worked around. > > So we need to prevent (5) if (1) and (3) already happened. Having a flag > set in the fbdev core somewhere when remove_conflicting_framebuffers() > is called could be a solution indeed. > > That is, the fbdev core needs to know that a DRM driver already probed > and make register_framebuffer() fail if info->flag & FBINFO_MISC_FIRMWARE > > I can attempt to write a patch for that. Ah yeah that could be an issue. I think the right fix is to replace the platform dev unregister with a sysfb_unregister() function in sysfb.c, which is synced with a common lock with the sysfb_init function and a small boolean. I think I can type that up quickly for v3. -Daniel > > -- > Best regards, > > Javier Martinez Canillas > Linux Engineering > Red Hat > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch