Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[Denis Gessert]

Hi,

I found this email chain while troubleshooting why my Levovo Duet
(with the MT8183 chip) would not boot using any 6.18.* kernel.

I can confirm that on my device the current stable 6.18.8 does not
boot unless I revert the commit

commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Date:   Thu Jul 24 10:39:08 2025 +0200

    arm64: dts: mediatek: mt8183: Migrate to display controller OF graph

mentioned below. With the reverted commit the device boots as intended.

PS: Apologies for the potential double-mail. My first message bounced
because it was HTML, so I am sending it again text-only. (This is my
first time on the mailing list..)

Cheers,

Denis

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[Thorsten Leemhuis]

On 2/6/26 12:33, Denis Gessert wrote:
> 
> I found this email chain while troubleshooting why my Levovo Duet
> (with the MT8183 chip) would not boot using any 6.18.* kernel.
> 
> I can confirm that on my device the current stable 6.18.8 does not
> boot unless I revert the commit
> 
> commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
> Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> Date:   Thu Jul 24 10:39:08 2025 +0200
> 
>     arm64: dts: mediatek: mt8183: Migrate to display controller OF graph
> 
> mentioned below. With the reverted commit the device boots as intended.

There is a fix for it from Otto here that I guess should help
https://lore.kernel.org/lkml/20260106-mt8183-display-graph-v2-1-e7e56054eef5@abscue.de/

Side note: lacks a stable tag and maybe should have been merged this
cycle instead of the next. But given that 6.19 is immanent it might be
good if this could be backported to 6.19.y once it landed in mainline.

> PS: Apologies for the potential double-mail. 
No worries, happens.

Ciao, Thortsten

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[Denis Gessert]

Thanks for the quick response. I compiled 6.18.9 with this patch
(without reverting the previous commit) and it boots successfully.

Cheers,
Denis

Am Fr., 6. Feb. 2026 um 15:55 Uhr schrieb Thorsten Leemhuis
<regressions@leemhuis.info>:
>
> On 2/6/26 12:33, Denis Gessert wrote:
> >
> > I found this email chain while troubleshooting why my Levovo Duet
> > (with the MT8183 chip) would not boot using any 6.18.* kernel.
> >
> > I can confirm that on my device the current stable 6.18.8 does not
> > boot unless I revert the commit
> >
> > commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
> > Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> > Date:   Thu Jul 24 10:39:08 2025 +0200
> >
> >     arm64: dts: mediatek: mt8183: Migrate to display controller OF graph
> >
> > mentioned below. With the reverted commit the device boots as intended.
>
> There is a fix for it from Otto here that I guess should help
> https://lore.kernel.org/lkml/20260106-mt8183-display-graph-v2-1-e7e56054eef5@abscue.de/
>
> Side note: lacks a stable tag and maybe should have been merged this
> cycle instead of the next. But given that 6.19 is immanent it might be
> good if this could be backported to 6.19.y once it landed in mainline.
>
> > PS: Apologies for the potential double-mail.
> No worries, happens.
>
> Ciao, Thortsten

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[AngeloGioacchino Del Regno]

Il 06/02/26 17:58, Denis Gessert ha scritto:
> Thanks for the quick response. I compiled 6.18.9 with this patch
> (without reverting the previous commit) and it boots successfully.
> 
> Cheers,
> Denis
> 

Well, I missed all those replies to this thread, and sent a redundant reply
saying .. well, the same as Thorsten (hey, thanks for being faster than me!).


Happy to see further confirmation that the patch that we both mentioned is
actually fixing the issue.

Cheers!
Angelo

> Am Fr., 6. Feb. 2026 um 15:55 Uhr schrieb Thorsten Leemhuis
> <regressions@leemhuis.info>:
>>
>> On 2/6/26 12:33, Denis Gessert wrote:
>>>
>>> I found this email chain while troubleshooting why my Levovo Duet
>>> (with the MT8183 chip) would not boot using any 6.18.* kernel.
>>>
>>> I can confirm that on my device the current stable 6.18.8 does not
>>> boot unless I revert the commit
>>>
>>> commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
>>> Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
>>> Date:   Thu Jul 24 10:39:08 2025 +0200
>>>
>>>      arm64: dts: mediatek: mt8183: Migrate to display controller OF graph
>>>
>>> mentioned below. With the reverted commit the device boots as intended.
>>
>> There is a fix for it from Otto here that I guess should help
>> https://lore.kernel.org/lkml/20260106-mt8183-display-graph-v2-1-e7e56054eef5@abscue.de/
>>
>> Side note: lacks a stable tag and maybe should have been merged this
>> cycle instead of the next. But given that 6.19 is immanent it might be
>> good if this could be backported to 6.19.y once it landed in mainline.
>>
>>> PS: Apologies for the potential double-mail.
>> No worries, happens.
>>
>> Ciao, Thortsten

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[Thorsten Leemhuis]

On 2/9/26 12:42, AngeloGioacchino Del Regno wrote:
> Il 06/02/26 17:58, Denis Gessert ha scritto:
>> Thanks for the quick response. I compiled 6.18.9 with this patch
>> (without reverting the previous commit) and it boots successfully.
> 
> Well, I missed all those replies to this thread, and sent a redundant reply
> saying .. well, the same as Thorsten (hey, thanks for being faster than
> me!).

Happens. :-D

> Happy to see further confirmation that the patch that we both mentioned is
> actually fixing the issue.

The big question remains: Now that this landed in mainline, should we as
the stable team to pick this up for 6.18.y and 6.19.y to get it resolved
there quickly? They might pick it up on their own due to the Fixes tag,
but that is not guaranteed.

Ciao, Thorsten

>> Am Fr., 6. Feb. 2026 um 15:55 Uhr schrieb Thorsten Leemhuis
>> <regressions@leemhuis.info>:
>>>
>>> On 2/6/26 12:33, Denis Gessert wrote:
>>>>
>>>> I found this email chain while troubleshooting why my Levovo Duet
>>>> (with the MT8183 chip) would not boot using any 6.18.* kernel.
>>>>
>>>> I can confirm that on my device the current stable 6.18.8 does not
>>>> boot unless I revert the commit
>>>>
>>>> commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
>>>> Author: AngeloGioacchino Del Regno
>>>> <angelogioacchino.delregno@collabora.com>
>>>> Date:   Thu Jul 24 10:39:08 2025 +0200
>>>>
>>>>      arm64: dts: mediatek: mt8183: Migrate to display controller OF
>>>> graph
>>>>
>>>> mentioned below. With the reverted commit the device boots as intended.
>>>
>>> There is a fix for it from Otto here that I guess should help
>>> https://lore.kernel.org/lkml/20260106-mt8183-display-graph-v2-1-
>>> e7e56054eef5@abscue.de/
>>>
>>> Side note: lacks a stable tag and maybe should have been merged this
>>> cycle instead of the next. But given that 6.19 is immanent it might be
>>> good if this could be backported to 6.19.y once it landed in mainline.
>>>
>>>> PS: Apologies for the potential double-mail.
>>> No worries, happens.
>>>
>>> Ciao, Thortsten
> 
> 
> 

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[AngeloGioacchino Del Regno]

Il 13/02/26 10:27, Thorsten Leemhuis ha scritto:
> On 2/9/26 12:42, AngeloGioacchino Del Regno wrote:
>> Il 06/02/26 17:58, Denis Gessert ha scritto:
>>> Thanks for the quick response. I compiled 6.18.9 with this patch
>>> (without reverting the previous commit) and it boots successfully.
>>
>> Well, I missed all those replies to this thread, and sent a redundant reply
>> saying .. well, the same as Thorsten (hey, thanks for being faster than
>> me!).
> 
> Happens. :-D
> 
>> Happy to see further confirmation that the patch that we both mentioned is
>> actually fixing the issue.
> 
> The big question remains: Now that this landed in mainline, should we as
> the stable team to pick this up for 6.18.y and 6.19.y to get it resolved
> there quickly? They might pick it up on their own due to the Fixes tag,
> but that is not guaranteed.
> 

Yes, please, that'd be great.

Cheers,
Angelo

> Ciao, Thorsten
> 
>>> Am Fr., 6. Feb. 2026 um 15:55 Uhr schrieb Thorsten Leemhuis
>>> <regressions@leemhuis.info>:
>>>>
>>>> On 2/6/26 12:33, Denis Gessert wrote:
>>>>>
>>>>> I found this email chain while troubleshooting why my Levovo Duet
>>>>> (with the MT8183 chip) would not boot using any 6.18.* kernel.
>>>>>
>>>>> I can confirm that on my device the current stable 6.18.8 does not
>>>>> boot unless I revert the commit
>>>>>
>>>>> commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
>>>>> Author: AngeloGioacchino Del Regno
>>>>> <angelogioacchino.delregno@collabora.com>
>>>>> Date:   Thu Jul 24 10:39:08 2025 +0200
>>>>>
>>>>>       arm64: dts: mediatek: mt8183: Migrate to display controller OF
>>>>> graph
>>>>>
>>>>> mentioned below. With the reverted commit the device boots as intended.
>>>>
>>>> There is a fix for it from Otto here that I guess should help
>>>> https://lore.kernel.org/lkml/20260106-mt8183-display-graph-v2-1-
>>>> e7e56054eef5@abscue.de/
>>>>
>>>> Side note: lacks a stable tag and maybe should have been merged this
>>>> cycle instead of the next. But given that 6.19 is immanent it might be
>>>> good if this could be backported to 6.19.y once it landed in mainline.
>>>>
>>>>> PS: Apologies for the potential double-mail.
>>>> No worries, happens.
>>>>
>>>> Ciao, Thortsten
>>
>>
>>
> 

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[Thorsten Leemhuis]

On 2/16/26 11:46, AngeloGioacchino Del Regno wrote:
> Il 13/02/26 10:27, Thorsten Leemhuis ha scritto:
>> On 2/9/26 12:42, AngeloGioacchino Del Regno wrote:
>>> Il 06/02/26 17:58, Denis Gessert ha scritto:
>>>> Thanks for the quick response. I compiled 6.18.9 with this patch
>>>> (without reverting the previous commit) and it boots successfully.
>>> Happy to see further confirmation that the patch that we both
>>> mentioned is
>>> actually fixing the issue.
>> The big question remains: Now that this landed in mainline, should we as
>> the stable team to pick this up for 6.18.y and 6.19.y to get it resolved
>> there quickly? They might pick it up on their own due to the Fixes tag,
>> but that is not guaranteed.
> Yes, please, that'd be great.

Hi stable team! Could you please pick up be0b304eeb8c5f ("arm64: dts:
mediatek: mt8183: Add missing endpoint IDs to display graph") [merged
v6.19-post, committed by Angelo, who ACKed this request; see quote
above] for 6.18.y and 6.19.y? It fixes a regression in e72d63fa0563
("arm64: dts: mediatek: mt8183: Migrate to display controller OF
graph"). tia! Ciao, Thorsten

>>>> Am Fr., 6. Feb. 2026 um 15:55 Uhr schrieb Thorsten Leemhuis
>>>> <regressions@leemhuis.info>:
>>>>>
>>>>> On 2/6/26 12:33, Denis Gessert wrote:
>>>>>>
>>>>>> I found this email chain while troubleshooting why my Levovo Duet
>>>>>> (with the MT8183 chip) would not boot using any 6.18.* kernel.
>>>>>>
>>>>>> I can confirm that on my device the current stable 6.18.8 does not
>>>>>> boot unless I revert the commit
>>>>>>
>>>>>> commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
>>>>>> Author: AngeloGioacchino Del Regno
>>>>>> <angelogioacchino.delregno@collabora.com>
>>>>>> Date:   Thu Jul 24 10:39:08 2025 +0200
>>>>>>
>>>>>>       arm64: dts: mediatek: mt8183: Migrate to display controller OF
>>>>>> graph
>>>>>>
>>>>>> mentioned below. With the reverted commit the device boots as
>>>>>> intended.
>>>>>
>>>>> There is a fix for it from Otto here that I guess should help
>>>>> https://lore.kernel.org/lkml/20260106-mt8183-display-graph-v2-1-
>>>>> e7e56054eef5@abscue.de/
>>>>>
>>>>> Side note: lacks a stable tag and maybe should have been merged this
>>>>> cycle instead of the next. But given that 6.19 is immanent it might be
>>>>> good if this could be backported to 6.19.y once it landed in mainline.
>>>>>
>>>>>> PS: Apologies for the potential double-mail.
>>>>> No worries, happens.
>>>>>
>>>>> Ciao, Thortsten
>>>
>>>
>>>
>>
> 
> 
> 

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[Greg KH]

On Tue, Feb 17, 2026 at 09:18:00AM +0100, Thorsten Leemhuis wrote:
> On 2/16/26 11:46, AngeloGioacchino Del Regno wrote:
> > Il 13/02/26 10:27, Thorsten Leemhuis ha scritto:
> >> On 2/9/26 12:42, AngeloGioacchino Del Regno wrote:
> >>> Il 06/02/26 17:58, Denis Gessert ha scritto:
> >>>> Thanks for the quick response. I compiled 6.18.9 with this patch
> >>>> (without reverting the previous commit) and it boots successfully.
> >>> Happy to see further confirmation that the patch that we both
> >>> mentioned is
> >>> actually fixing the issue.
> >> The big question remains: Now that this landed in mainline, should we as
> >> the stable team to pick this up for 6.18.y and 6.19.y to get it resolved
> >> there quickly? They might pick it up on their own due to the Fixes tag,
> >> but that is not guaranteed.
> > Yes, please, that'd be great.
> 
> Hi stable team! Could you please pick up be0b304eeb8c5f ("arm64: dts:
> mediatek: mt8183: Add missing endpoint IDs to display graph") [merged
> v6.19-post, committed by Angelo, who ACKed this request; see quote
> above] for 6.18.y and 6.19.y? It fixes a regression in e72d63fa0563
> ("arm64: dts: mediatek: mt8183: Migrate to display controller OF
> graph"). tia! Ciao, Thorsten

Now queued up, thanks.

greg k-h

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[AngeloGioacchino Del Regno]

Il 06/02/26 12:33, Denis Gessert ha scritto:
> Hi,
> 
> I found this email chain while troubleshooting why my Levovo Duet
> (with the MT8183 chip) would not boot using any 6.18.* kernel.
> 
> I can confirm that on my device the current stable 6.18.8 does not
> boot unless I revert the commit
> 
> commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
> Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> Date:   Thu Jul 24 10:39:08 2025 +0200
> 
>      arm64: dts: mediatek: mt8183: Migrate to display controller OF graph
> 
> mentioned below. With the reverted commit the device boots as intended.
> 
> PS: Apologies for the potential double-mail. My first message bounced
> because it was HTML, so I am sending it again text-only. (This is my
> first time on the mailing list..)
> 
> Cheers,
> 
> Denis

Hello Denis,

This patch should be resolving the issue -> 
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/arch/arm64/boot/dts/mediatek?h=next-20260205&id=be0b304eeb8c5f77e4f98f64e58729d879195f2f


Cheers,
Angelo

Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[Evans Jahja]

Hi Angelo, I was able to isolate the problem further to the dts. After
bisecting the arch/arm64/boot/dts/mediatek/ and building the dts, it
seems like this is the first commit that introduced the issue on my
device.

commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Date:   Thu Jul 24 10:39:08 2025 +0200

    arm64: dts: mediatek: mt8183: Migrate to display controller OF graph

I am linking my full bisect log here:

https://bugzilla.kernel.org/attachment.cgi?id=308962&action=edit

Thank you,

Evans Jahja

On Wed, Nov 26, 2025 at 3:01 AM Evans Jahja <evansjahja13@gmail.com> wrote:
>
> Hi,
>
> I have a Lenovo IdeaPad Duet Chromebook CT-X636F, detected as Mediatek
> krane sku176 board. (mt8183-kukui-krane)
>
> The display failed to initialize on the mainline kernel (linux
> 6.18-rc7). Using the same config, on stable (linux 6.17.9) the display
> works fine.
>
> config: https://bugzilla.kernel.org/show_bug.cgi?id=220803
>
> With the system on mainline kernel, I was able to check the serial
> console, the error on dmesg looks like this:
>
> [    6.513400] mediatek-drm mediatek-drm.18.auto: Building display
> pipeline for MMSYS 0
> [    6.514983] mediatek-drm mediatek-drm.18.auto: Display HW Pipeline
> built with 9 components.
> [    6.515009] mediatek-drm mediatek-drm.18.auto: Invalid display hw
> pipeline. Last component: 38 (ret=-2)
> [    6.524422] mediatek-drm mediatek-drm.18.auto: probe with driver
> mediatek-drm failed with error -22
>
> Temporarily modifying mtk_drm_drv.c by commenting calls to
> mtk_drm_of_ddp_path_build_one CRTC_EXT and CRTC_THIRD allows the
> display to function even on mainline. I was also able to add some
> logging and determine that building the HW pipeline for CRTC_MAIN
> works, but because building CRTC_EXT fails, the entire display would
> not initialize.
>
> I am on ArchLinuxARM, its prebuilt kernel was based on linux 6.17.8
> with distro-specific patches, also failed to init display. I have not
> checked why that failed, I am currently focusing on a clean upstream
> kernel.
>
> Please let me know how I can help. My apologies but I am rather new
> and may confuse terminologies. I will update as I learn more about the
> issue.
>
> Best regards,
>
> Evans Jahja

[REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[Evans Jahja]

#regzbot ^introduced: e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6
#regzbot monitor: https://bugzilla.kernel.org/attachment.cgi?id=308962
Hi,

There has been a regression in the dts for my system
mt8183-kukui-krane, where changes in dts/mediatek/mt8183.dtsi broke my
machine.

The display works under v6.17.9 but is broken in v6.18-rc7. I was able
to replicate / fix the issue just by using the dts from the other
version.

> On Wed, Nov 26, 2025 at 3:01 AM Evans Jahja <evansjahja13@gmail.com> wrote:
> >
> > Hi,
> >
> > I have a Lenovo IdeaPad Duet Chromebook CT-X636F, detected as Mediatek
> > krane sku176 board. (mt8183-kukui-krane)
> >
> > The display failed to initialize on the mainline kernel (linux
> > 6.18-rc7). Using the same config, on stable (linux 6.17.9) the display
> > works fine.
> >
> > config: https://bugzilla.kernel.org/show_bug.cgi?id=220803
> >
> > With the system on mainline kernel, I was able to check the serial
> > console, the error on dmesg looks like this:
> >
> > [    6.513400] mediatek-drm mediatek-drm.18.auto: Building display
> > pipeline for MMSYS 0
> > [    6.514983] mediatek-drm mediatek-drm.18.auto: Display HW Pipeline
> > built with 9 components.
> > [    6.515009] mediatek-drm mediatek-drm.18.auto: Invalid display hw
> > pipeline. Last component: 38 (ret=-2)
> > [    6.524422] mediatek-drm mediatek-drm.18.auto: probe with driver
> > mediatek-drm failed with error -22
> >
> > Temporarily modifying mtk_drm_drv.c by commenting calls to
> > mtk_drm_of_ddp_path_build_one CRTC_EXT and CRTC_THIRD allows the
> > display to function even on mainline. I was also able to add some
> > logging and determine that building the HW pipeline for CRTC_MAIN
> > works, but because building CRTC_EXT fails, the entire display would
> > not initialize.
> >

I think this is the issue:
https://lkml.org/lkml/2025/9/12/1242

On Wed, Nov 26, 2025 at 2:06 PM Evans Jahja <evansjahja13@gmail.com> wrote:
>
> Hi Angelo, I was able to isolate the problem further to the dts. After
> bisecting the arch/arm64/boot/dts/mediatek/ and building the dts, it
> seems like this is the first commit that introduced the issue on my
> device.
>
> commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
> Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> Date:   Thu Jul 24 10:39:08 2025 +0200
>
>     arm64: dts: mediatek: mt8183: Migrate to display controller OF graph
>
> I am linking my full bisect log here:
>
> https://bugzilla.kernel.org/attachment.cgi?id=308962&action=edit

where we're unconditionally adding mmsys_ep_ext.

The issue seems to be caused by the recent addition of CRTC_EXT on the
base mt8183

Please kindly take a look. Apologies for any mistake, this is my first issue.

Evans Jahja

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[Evans Jahja]

#regzbot introduced: v6.17..e72d63fa0563
#regzbot monitor: https://bugzilla.kernel.org/attachment.cgi?id=308962

Re: [REGRESSION] mt8183-kukui: dts: changes in dts caused display to no longer initialize - Was: Re: mt8183-kukui: drm/mediatek: dts: Invalid display hw pipeline when probing mediatek-drm

[Thorsten Leemhuis]

Lo!

Matthias, AngeloGioacchino, have you maybe looked into regression that
seems to be caused by 72d63fa0563f8 ("arm64: dts: mediatek: mt8183:
Migrate to display controller OF graph")?

Evans Jahja, just to be sure: I suppose it still happens with 6.18
final? And have you tried if reverting the change fixes this ("fix the
issue just by using the dts from the other version" might have changed
other things as well, that's why I'm asking)

Ciao, Thorsten

On 11/28/25 03:59, Evans Jahja wrote:
> Hi,
> 
> There has been a regression in the dts for my system
> mt8183-kukui-krane, where changes in dts/mediatek/mt8183.dtsi broke my
> machine.
> 
> The display works under v6.17.9 but is broken in v6.18-rc7. I was able
> to replicate / fix the issue just by using the dts from the other
> version.
> 
>> On Wed, Nov 26, 2025 at 3:01 AM Evans Jahja <evansjahja13@gmail.com> wrote:
>>>
>>> Hi,
>>>
>>> I have a Lenovo IdeaPad Duet Chromebook CT-X636F, detected as Mediatek
>>> krane sku176 board. (mt8183-kukui-krane)
>>>
>>> The display failed to initialize on the mainline kernel (linux
>>> 6.18-rc7). Using the same config, on stable (linux 6.17.9) the display
>>> works fine.
>>>
>>> config: https://bugzilla.kernel.org/show_bug.cgi?id=220803
>>>
>>> With the system on mainline kernel, I was able to check the serial
>>> console, the error on dmesg looks like this:
>>>
>>> [    6.513400] mediatek-drm mediatek-drm.18.auto: Building display
>>> pipeline for MMSYS 0
>>> [    6.514983] mediatek-drm mediatek-drm.18.auto: Display HW Pipeline
>>> built with 9 components.
>>> [    6.515009] mediatek-drm mediatek-drm.18.auto: Invalid display hw
>>> pipeline. Last component: 38 (ret=-2)
>>> [    6.524422] mediatek-drm mediatek-drm.18.auto: probe with driver
>>> mediatek-drm failed with error -22
>>>
>>> Temporarily modifying mtk_drm_drv.c by commenting calls to
>>> mtk_drm_of_ddp_path_build_one CRTC_EXT and CRTC_THIRD allows the
>>> display to function even on mainline. I was also able to add some
>>> logging and determine that building the HW pipeline for CRTC_MAIN
>>> works, but because building CRTC_EXT fails, the entire display would
>>> not initialize.
>>>
> 
> I think this is the issue:
> https://lkml.org/lkml/2025/9/12/1242
> 
> On Wed, Nov 26, 2025 at 2:06 PM Evans Jahja <evansjahja13@gmail.com> wrote:
>>
>> Hi Angelo, I was able to isolate the problem further to the dts. After
>> bisecting the arch/arm64/boot/dts/mediatek/ and building the dts, it
>> seems like this is the first commit that introduced the issue on my
>> device.
>>
>> commit e72d63fa0563f8a6e98c10fed3a9ce74dc0536e6 (HEAD)
>> Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
>> Date:   Thu Jul 24 10:39:08 2025 +0200
>>
>>     arm64: dts: mediatek: mt8183: Migrate to display controller OF graph
>>
>> I am linking my full bisect log here:
>>
>> https://bugzilla.kernel.org/attachment.cgi?id=308962&action=edit
> 
> where we're unconditionally adding mmsys_ep_ext.
> 
> The issue seems to be caused by the recent addition of CRTC_EXT on the
> base mt8183
> 
> Please kindly take a look. Apologies for any mistake, this is my first issue.
> 
> Evans Jahja
> 
>