Message-ID: <ZUsbO7syWsbiCcdo@P70.localdomain>
Date:   Tue, 7 Nov 2023 21:23:07 -0800
From:   Evan Preston <x.arch@...eston.net>
To:     Evan Preston <x.arch@...eston.net>
Cc:     Huacai Chen <chenhuacai@...nel.org>,
        Linux regressions mailing list <regressions@...ts.linux.dev>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Linux DRI Development <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Jaak Ristioja <jaak@...tioja.ee>,
        Bagas Sanjaya <bagasdotme@...il.com>
Subject: Re: Blank screen on boot of Linux 6.5 and later on Lenovo ThinkPad
 L570

On 2023-11-06 Mon 09:39pm, Evan Preston wrote:
> Hi Huacai,
> 
> On 2023-11-07 Tue 09:49am, Huacai Chen wrote:
> > Hi, Evan,
> > 
> > On Tue, Nov 7, 2023 at 4:32 AM Evan Preston <x.arch@...eston.net> wrote:
> > >
> > > Hi Huacai,
> > >
> > > On 2023-11-06 Mon 10:22pm, Huacai Chen wrote:
> > > > On Mon, Nov 6, 2023 at 9:49 PM Jaak Ristioja <jaak@...tioja.ee> wrote:
> > > > >
> > > > > On 06.11.23 04:15, Huacai Chen wrote:
> > > > > > Hi, Jaak and Evan,
> > > > > >
> > > > > > On Mon, Nov 6, 2023 at 12:28 AM Jaak Ristioja <jaak@...tioja.ee> wrote:
> > > > > >>
> > > > > >> On 05.11.23 14:40, Huacai Chen wrote:
> > > > > >>> Hi, Evan,
> > > > > >>>
> > > > > >>> On Sat, Nov 4, 2023 at 10:50 AM Evan Preston <x.arch@...eston.net> wrote:
> > > > > >>>>
> > > > > >>>> Hi Huacai,
> > > > > >>>>
> > > > > >>>> On 2023-11-03 Fri 02:36pm, Huacai Chen wrote:
> > > > > >>>>> Hi, Evan,
> > > > > >>>>>
> > > > > >>>>> On Fri, Nov 3, 2023 at 1:54 PM Evan Preston <x.arch@...eston.net> wrote:
> > > > > >>>>>>
> > > > > >>>>>> Hi Huacai,
> > > > > >>>>>>
> > > > > >>>>>> On 2023-11-02 Thu 08:38pm, Huacai Chen wrote:
> > > > > >>>>>>> Hi, Jaak,
> > > > > >>>>>>>
> > > > > >>>>>>> On Wed, Nov 1, 2023 at 7:52 PM Jaak Ristioja <jaak@...tioja.ee> wrote:
> > > > > >>>>>>>>
> > > > > >>>>>>>> On 31.10.23 14:17, Huacai Chen wrote:
> > > > > >>>>>>>>> Hi, Jaak and Evan,
> > > > > >>>>>>>>>
> > > > > >>>>>>>>> On Sun, Oct 29, 2023 at 9:42 AM Huacai Chen <chenhuacai@...nel.org> wrote:
> > > > > >>>>>>>>>>
> > > > > >>>>>>>>>> On Sat, Oct 28, 2023 at 7:06 PM Jaak Ristioja <jaak@...tioja.ee> wrote:
> > > > > >>>>>>>>>>>
> > > > > >>>>>>>>>>> On 26.10.23 03:58, Huacai Chen wrote:
> > > > > >>>>>>>>>>>> Hi, Jaak,
> > > > > >>>>>>>>>>>>
> > > > > >>>>>>>>>>>> On Thu, Oct 26, 2023 at 2:49 AM Jaak Ristioja <jaak@...tioja.ee> wrote:
> > > > > >>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>> On 25.10.23 16:23, Huacai Chen wrote:
> > > > > >>>>>>>>>>>>>> On Wed, Oct 25, 2023 at 6:08 PM Thorsten Leemhuis
> > > > > >>>>>>>>>>>>>> <regressions@...mhuis.info> wrote:
> > > > > >>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>> Javier, Dave, Sima,
> > > > > >>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>> On 23.10.23 00:54, Evan Preston wrote:
> > > > > >>>>>>>>>>>>>>>> On 2023-10-20 Fri 05:48pm, Huacai Chen wrote:
> > > > > >>>>>>>>>>>>>>>>> On Fri, Oct 20, 2023 at 5:35 PM Linux regression tracking (Thorsten
> > > > > >>>>>>>>>>>>>>>>> Leemhuis) <regressions@...mhuis.info> wrote:
> > > > > >>>>>>>>>>>>>>>>>> On 09.10.23 10:54, Huacai Chen wrote:
> > > > > >>>>>>>>>>>>>>>>>>> On Mon, Oct 9, 2023 at 4:45 PM Bagas Sanjaya <bagasdotme@...il.com> wrote:
> > > > > >>>>>>>>>>>>>>>>>>>> On Mon, Oct 09, 2023 at 09:27:02AM +0800, Huacai Chen wrote:
> > > > > >>>>>>>>>>>>>>>>>>>>> On Tue, Sep 26, 2023 at 10:31 PM Huacai Chen <chenhuacai@...nel.org> wrote:
> > > > > >>>>>>>>>>>>>>>>>>>>>> On Tue, Sep 26, 2023 at 7:15 PM Linux regression tracking (Thorsten
> > > > > >>>>>>>>>>>>>>>>>>>>>> Leemhuis) <regressions@...mhuis.info> wrote:
> > > > > >>>>>>>>>>>>>>>>>>>>>>> On 13.09.23 14:02, Jaak Ristioja wrote:
> > > > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>>>>>>>>> Upgrading to Linux 6.5 on a Lenovo ThinkPad L570 (Integrated Intel HD
> > > > > >>>>>>>>>>>>>>>>>>>>>>>> Graphics 620 (rev 02), Intel(R) Core(TM) i7-7500U) results in a blank
> > > > > >>>>>>>>>>>>>>>>>>>>>>>> screen after boot until the display manager starts... if it does start
> > > > > >>>>>>>>>>>>>>>>>>>>>>>> at all. Using the nomodeset kernel parameter seems to be a workaround.
> > > > > >>>>>>>>>>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>>>>>>>>> I've bisected this to commit 60aebc9559492cea6a9625f514a8041717e3a2e4
> > > > > >>>>>>>>>>>>>>>>>>>>>>>> ("drivers/firmware: Move sysfb_init() from device_initcall to
> > > > > >>>>>>>>>>>>>>>>>>>>>>>> subsys_initcall_sync").
> > > > > >>>>>>>>>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>>>>>> As confirmed by Jaak, disabling DRM_SIMPLEDRM makes things work fine
> > > > > >>>>>>>>>>>>>>>>>>>>> again. So I guess the reason:
> > > > > >>>>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>>> Well, this to me still looks a lot (please correct me if I'm wrong) like
> > > > > >>>>>>>>>>>>>>>>>> regression that should be fixed, as DRM_SIMPLEDRM was enabled beforehand
> > > > > >>>>>>>>>>>>>>>>>> if I understood things correctly. Or is there a proper fix for this
> > > > > >>>>>>>>>>>>>>>>>> already in the works and I just missed this? Or is there some good
> > > > > >>>>>>>>>>>>>>>>>> reason why this won't/can't be fixed?
> > > > > >>>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>> DRM_SIMPLEDRM was enabled but it didn't work at all because there was
> > > > > >>>>>>>>>>>>>>>>> no corresponding platform device. Now DRM_SIMPLEDRM works but it has a
> > > > > >>>>>>>>>>>>>>>>> blank screen. Of course it is valuable to investigate further about
> > > > > >>>>>>>>>>>>>>>>> DRM_SIMPLEDRM on Jaak's machine, but that needs Jaak's effort because
> > > > > >>>>>>>>>>>>>>>>> I don't have a same machine.
> > > > > >>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>> Side note: Huacai, have you tried working with Jaak to get down to the
> > > > > >>>>>>>>>>>>>>> real problem? Evan, might you be able to help out here?
> > > > > >>>>>>>>>>>>>> No, Jaak has no response after he 'fixed' his problem by disabling SIMPLEDRM.
> > > > > >>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>> I'm sorry, what was it exactly you want me to do? Please be mindful that
> > > > > >>>>>>>>>>>>> I'm not familiar with the internals of the Linux kernel and DRI, and it
> > > > > >>>>>>>>>>>>> might sometimes take weeks before I have time to work and respond on this.
> > > > > >>>>>>>>>>>> It doesn't matter. I hope you can do some experiments to investigate
> > > > > >>>>>>>>>>>> deeper. The first experiment you can do is enabling SIMPLEFB (i.e.
> > > > > >>>>>>>>>>>> CONFIG_FB_SIMPLE) instead of SIMPLEDRM (CONFIG_DRM_SIMPLEDRM) to see
> > > > > >>>>>>>>>>>> whether there is also a blank screen. If no blank screen, that
> > > > > >>>>>>>>>>>> probably means SIMPLEDRM has a bug, if still blank screen, that means
> > > > > >>>>>>>>>>>> the firmware may pass wrong screen information.
> > > > > >>>>>>>>>>>
> > > > > >>>>>>>>>>> Testing with 6.5.9 I get a blank screen with CONFIG_DRM_SIMPLEDRM=y and
> > > > > >>>>>>>>>>> get no blank screen with CONFIG_FB_SIMPLE=y and CONFIG_DRM_SIMPLEDRM unset.
> > > > > >>>>>>>>>> CONFIG_FB_SIMPLE and  CONFIG_DRM_SIMPLEDRM use the same device created
> > > > > >>>>>>>>>> by sysfb_init(). Since FB_SIMPLE works fine, I think the real problem
> > > > > >>>>>>>>>> is that DRM_SIMPLEDRM has a bug. The next step is to enable
> > > > > >>>>>>>>>> CONFIG_DRM_SIMPLEDRM and trace its initialization. In detail, adding
> > > > > >>>>>>>>>> some printk() in simpledrm_probe() and its sub-routines to see where
> > > > > >>>>>>>>>> the driver fails. The output of these printk() can be seen by the
> > > > > >>>>>>>>>> 'dmesg' command after boot.
> > > > > >>>>>>>>> I need your help. I tried with my laptop (ThinkPad E490, Intel Core
> > > > > >>>>>>>>> i3-8145U, UHD Graphics 620) but I can't reproduce your problem. So
> > > > > >>>>>>>>> please patch your 6.5.x kernel with this temporary patch [1], then
> > > > > >>>>>>>>> build a "bad kernel" with SIMPLEDRM enabled. And after booting your
> > > > > >>>>>>>>> machine with this "bad kernel", please give me the dmesg output. Thank
> > > > > >>>>>>>>> you very much.
> > > > > >>>>>>>>>
> > > > > >>>>>>>>> [1] http://ddns.miaomiaomiao.top:9000/download/kernel/patch-6.5.9
> > > > > >>>>>>>>
> > > > > >>>>>>>> I'm unable to download it. Can you please send it by e-mail?
> > > > > >>>>>>> I'm sorry, please download from attachment.
> > > > > >>>>>>
> > > > > >>>>>> When applying this patch the first hunk (drivers/firmware/sysfb.c) fails for
> > > > > >>>>>> me with 6.5.9.  Attempting to load the 6.5.9 kernel without this patch
> > > > > >>>>>> produces no dmesg output on my machine.
> > > > > >>>>> You copy-paste the patch? If you download it directly it can be
> > > > > >>>>> applied successfully, I think.
> > > > > >>>>
> > > > > >>>> The patch downloaded from your URL applies successfully.  However, I still
> > > > > >>>> see no dmesg output using the patched 6.5.9 kernel.  'journalctl -k -b all'
> > > > > >>>> shows no dmesg output from any 6.5.x boots, only from 6.4.12 boots.
> > > > > >>> Thank you for your testing. Since you cannot boot to GUI successfully
> > > > > >>> as Jaak, you may have some troubles with getting the dmesg output. But
> > > > > >>> you can try to use "systemd.unit=multi-user.target" boot parameters.
> > > > > >>> In this way you may boot to the login: prompt and then you can get
> > > > > >>> dmesg output. Or if you still fail, you may use 'jornalctl -k -b -1'
> > > > > >>> to get the previous dmesg output with 6.4.12.
> > > > > >>>
> > > > > >>> Hi, Jaak,
> > > > > >>>
> > > > > >>> Have you tested? I think you can successfully get a dmesg output with my patch.
> > > > > >>
> > > > > >> Yes, just tested it, here I think are the relevant parts from a dmesg
> > > > > >> produced with CONFIG_DRM_SIMPLEDRM and the patch provided by Huacai:
> > > > > >>
> > > > > >> ...
> > > > > >> [    2.909625] sysfb 1
> > > > > >> [    2.909627] sysfb 2
> > > > > >> ...
> > > > > >> [    2.951477] ACPI: bus type drm_connector registered
> > > > > >> [    2.952096] i915 0000:00:02.0: [drm] VT-d active for gfx access
> > > > > >> [    2.952105] resource: resource sanity check: requesting [mem
> > > > > >> 0x00000000e0000000-0x00000000efffffff], which spans more than BOOTFB
> > > > > >> [mem 0xe0000000-0xe012bfff]
> > > > > >> [    2.952111] caller i915_ggtt_init_hw+0x88/0x120 mapping multiple BARs
> > > > > >> [    2.952138] i915 0000:00:02.0: [drm] Using Transparent Hugepages
> > > > > >> [    2.953204] Loading firmware: i915/kbl_dmc_ver1_04.bin
> > > > > >> [    2.953485] i915 0000:00:02.0: [drm] Finished loading DMC firmware
> > > > > >> i915/kbl_dmc_ver1_04.bin (v1.4)
> > > > > >> ...
> > > > > >> [    4.142075] [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on
> > > > > >> minor 0
> > > > > >> [    4.144269] ACPI: video: Video Device [GFX0] (multi-head: yes  rom:
> > > > > >> no  post: no)
> > > > > >> [    4.144414] input: Video Bus as
> > > > > >> /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input4
> > > > > >> [    4.144580] [drm] Initialized vgem 1.0.0 20120112 for vgem on minor 1
> > > > > >> [    4.144590] usbcore: registered new interface driver udl
> > > > > >> [    4.144603] T: probe 1
> > > > > >> [    4.144605] T: create 1
> > > > > >> [    4.144610] T: create 2
> > > > > >> [    4.144611] T: create 3a-1
> > > > > >> [    4.144613] T: create 3a-2
> > > > > >> [    4.144614] T: create 3a-3
> > > > > >> [    4.144616] T: create 3a-4
> > > > > >> [    4.144618] T: create 4
> > > > > >> [    4.144619] T: create 5
> > > > > >> [    4.144621] simple-framebuffer simple-framebuffer.0: [drm] display
> > > > > >> mode={"": 60 18432 640 640 640 640 480 480 480 480 0x40 0x0}
> > > > > >> [    4.144628] simple-framebuffer simple-framebuffer.0: [drm]
> > > > > >> framebuffer format=XR24 little-endian (0x34325258), size=640x480,
> > > > > >> stride=2560 byte
> > > > > >> [    4.144633] T: create 6b-1
> > > > > >> [    4.144635] T: create 6b-2
> > > > > >> [    4.144637] simple-framebuffer simple-framebuffer.0: [drm] using I/O
> > > > > >> memory framebuffer at [mem 0xe0000000-0xe012bfff flags 0x200]
> > > > > >> [    4.144643] T: create 6b-3
> > > > > >> [    4.144660] T: create 6b-4
> > > > > >> [    4.144662] T: create 7
> > > > > >> [    4.144673] T: create 8
> > > > > >> [    4.144676] T: create 9
> > > > > >> [    4.144678] T: create 10
> > > > > >> [    4.144681] T: create 11
> > > > > >> [    4.144685] T: create 12
> > > > > >> [    4.144689] T: probe 2
> > > > > >> [    4.144728] [drm] Initialized simpledrm 1.0.0 20200625 for
> > > > > >> simple-framebuffer.0 on minor 2
> > > > > >> [    4.144732] T: probe 3
> > > > > >> [    4.145905] Console: switching to colour frame buffer device 80x30
> > > > > >> [    4.150437] simple-framebuffer simple-framebuffer.0: [drm] fb0:
> > > > > >> simpledrmdrmfb frame buffer device
> > > > > >> [    4.150766] T: probe 4
> > > > > >> [    4.151218] loop: module loaded
> > > > > >> [    4.154434] i915 0000:00:02.0: [drm] fb1: i915drmfb frame buffer device
> > > > > >> ...
> > > > > >> [   44.630789] simple-framebuffer simple-framebuffer.0: swiotlb buffer
> > > > > >> is full (sz: 1310720 bytes), total 32768 (slots), used 0 (slots)
> > > > > >> ...
> > > > > >>
> > > > > >> The last message might be due to the display manager starting up.
> > > > > >>
> > > > > >> Hope it helps.
> > > > > > Thank you for your testing. Jaak's problem seems related to the
> > > > > > initialization order, you can try to modify drivers/gpu/drm/Makefile,
> > > > > > move
> > > > > >
> > > > > > obj-y                  += tiny/
> > > > > >
> > > > > > to between these two lines
> > > > > >
> > > > > > obj-$(CONFIG_DRM_SCHED) += scheduler/
> > > > > > obj-$(CONFIG_DRM_RADEON)+= radeon/
> > > > > >
> > > > > > then build a new 6.5.x kernel to see whether your problem is resolved.
> > > > >
> > > > > Yes, this seems to have resolved it.
> > > > Hi, Jaak,
> > > >
> > > > Thank you very much, and I hope this also solves Evan's problem.
> > >
> > > I still get a blank screen if I modify drivers/gpu/drm/Makefile to move the
> > > order of 'tiny'.
> > You probably encounter another problem which has no relationship with
> > 60aebc9559492cea6a9625f514a804 ("drivers/firmware: Move sysfb_init()
> > from device_initcall to subsys_initcall_sync"). You can revert it to
> > test 6.5.x again.
> 
> You are right.  I reverted "drivers/firmware: Move sysfb_init() from 
> device_initcall to subsys_initcall_sync" on 6.5.9 and still get a blank 
> screen immediately after boot loader entry selection.
> 
> Evan
> 

Just to close the loop on my issue: after a BIOS update I can boot 6.5.x 
successfully.

Evan

> > 
> > Huacai
> > 
> > >
> > > >
> > > > Hi, Javier,
> > > >
> > > > I think I have mostly found the root cause. DRM_SIMPLEDRM has no bugs,
> > > > Jaak's problem is due to the initialization order of drivers, and this
> > > > order depends on the Makefile.
> > > >
> > > > FB_SIMPLE is before native DRM drivers (e.g. i915, radeon, amdgpu, and
> > > > so on), but DRM_SIMPLEDRM is after them. Thus, if Jaak uses FB_SIMPLE,
> > > > I915 will takeover FB_SIMPLE, then no problem; and if Jaak uses
> > > > DRM_SIMPLEDRM, DRM_SIMPLEDRM will try to takeover I915, but fails to
> > > > work.
> > > >
> > > > So, when I move the "tiny" directory before i915, the problem is
> > > > solved. But the new problem is: is it acceptable to solve this problem
> > > > by adjusting Makefile?
> > > >
> > > > Huacai
> > > >
> > > > >
> > > > > Jaak
> > > > >
> > > > > >
> > > > > > Evan's problem seems a little strange, could you please give me your
> > > > > > config files of both 6.4.12 and 6.5.x? And you can also try the above
> > > > > > method to see if anything changes.
> > >
> > > I'll send you my config files.
> > >
> > > > > >
> > > > > > Huacai
> > > > > >
> > > > > >>
> > > > > >> J
> > > > > >>
> > > > > >>>
> > > > > >>>>
> > > > > >>>> Evan
> > > > > >>>>
> > > > > >>>>>
> > > > > >>>>> Huacai
> > > > > >>>>>
> > > > > >>>>>>
> > > > > >>>>>> Evan
> > > > > >>>>>>
> > > > > >>>>>>>
> > > > > >>>>>>> Huacai
> > > > > >>>>>>>
> > > > > >>>>>>>>
> > > > > >>>>>>>> Jaak
> > > > > >>>>>>>>
> > > > > >>>>>>>>>
> > > > > >>>>>>>>>
> > > > > >>>>>>>>> Huacai
> > > > > >>>>>>>>>
> > > > > >>>>>>>>>>
> > > > > >>>>>>>>>> Huacai
> > > > > >>>>>>>>>>
> > > > > >>>>>>>>>>>
> > > > > >>>>>>>>>>> Jaak
> > > > > >>>>>>>>>>>
> > > > > >>>>>>>>>>>>
> > > > > >>>>>>>>>>>> Huacai
> > > > > >>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>> Jaak
> > > > > >>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>> But I write this mail for a different reason:
> > > > > >>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>> I am having the same issue on a Lenovo Thinkpad P70 (Intel
> > > > > >>>>>>>>>>>>>>>> Corporation HD Graphics 530 (rev 06), Intel(R) Core(TM) i7-6700HQ).
> > > > > >>>>>>>>>>>>>>>> Upgrading from Linux 6.4.12 to 6.5 and later results in only a blank
> > > > > >>>>>>>>>>>>>>>> screen after boot and a rapidly flashing device-access-status
> > > > > >>>>>>>>>>>>>>>> indicator.
> > > > > >>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>> This additional report makes me wonder if we should revert the culprit
> > > > > >>>>>>>>>>>>>>> (60aebc9559492c ("drivers/firmware: Move sysfb_init() from
> > > > > >>>>>>>>>>>>>>> device_initcall to subsys_initcall_sync") [v6.5-rc1]). But I guess that
> > > > > >>>>>>>>>>>>>>> might lead to regressions for some users? But the patch description says
> > > > > >>>>>>>>>>>>>>> that this is not a common configuration, so can we maybe get away with that?
> > > > > >>>>>>>>>>>>>>      From my point of view, this is not a regression, 60aebc9559492c
> > > > > >>>>>>>>>>>>>> doesn't cause a problem, but exposes a problem. So we need to fix the
> > > > > >>>>>>>>>>>>>> real problem (SIMPLEDRM has a blank screen on some conditions). This
> > > > > >>>>>>>>>>>>>> needs Jaak or Evan's help.
> > > > > >>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>> Huacai
> > > > > >>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> > > > > >>>>>>>>>>>>>>> --
> > > > > >>>>>>>>>>>>>>> Everything you wanna know about Linux kernel regression tracking:
> > > > > >>>>>>>>>>>>>>> https://linux-regtracking.leemhuis.info/about/#tldr
> > > > > >>>>>>>>>>>>>>> If I did something stupid, please tell me, as explained on that page.
> > > > > >>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>>>>>> When SIMPLEDRM takes over the framebuffer, the screen is blank (don't
> > > > > >>>>>>>>>>>>>>>>>>>>> know why). And before 60aebc9559492cea6a9625f ("drivers/firmware: Move
> > > > > >>>>>>>>>>>>>>>>>>>>> sysfb_init() from device_initcall to subsys_initcall_sync") there is
> > > > > >>>>>>>>>>>>>>>>>>>>> no platform device created for SIMPLEDRM at early stage, so it seems
> > > > > >>>>>>>>>>>>>>>>>>>>> also "no problem".
> > > > > >>>>>>>>>>>>>>>>>>>> I don't understand above. You mean that after that commit the platform
> > > > > >>>>>>>>>>>>>>>>>>>> device is also none, right?
> > > > > >>>>>>>>>>>>>>>>>>> No. The SIMPLEDRM driver needs a platform device to work, and that
> > > > > >>>>>>>>>>>>>>>>>>> commit makes the platform device created earlier. So, before that
> > > > > >>>>>>>>>>>>>>>>>>> commit, SIMPLEDRM doesn't work, but the screen isn't blank; after that
> > > > > >>>>>>>>>>>>>>>>>>> commit, SIMPLEDRM works, but the screen is blank.
> > > > > >>>>>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>>>> Huacai
> > > > > >>>>>>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>>>>> Confused...
> > > > > >>>>>>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>>>>> --
> > > > > >>>>>>>>>>>>>>>>>>>> An old man doll... just what I always wanted! - Clara
> > > > > >>>>>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>>>>
> > > > > >>>>>>>>>>>>>
> > > > > >>>>>>>>>>>
> > > > > >>>>>>>>
> > > > > >>>>>>
> > > > > >>>>>>
> > > > > >>
> > > > >

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