Re: [PATCH v2 5/5] arm64: dts: qcom: sdm845-xiaomi-beryllium-tianma: Disable MDSS

Re: [PATCH v2 5/5] arm64: dts: qcom: sdm845-xiaomi-beryllium-tianma: Disable MDSS

[David Heidelberg]

On 18/03/2026 15:47, Dmitry Baryshkov wrote:
> On Tue, Mar 17, 2026 at 11:12:35PM +0100, David Heidelberg via B4 Relay wrote:
>> From: Petr Hodina <petr.hodina@protonmail.com>
>>
>> Currently the panel driver for tianma is broken.
>> Disable MDSS to prevent DRM taking over the framebuffer.
> 
> I'd still hope that somebody can get it to work. I'd start by using
> prepare_prev_first. Sumit reported the panel as working in 2020 and I
> have no doubts that it was the case. Another option migt be something
> related to the dispcc (see my [1]).

Sadly, the prepare_prev_first didn't solve the issue. The framebuffer -> MDSS 
takover happens, but at greetd (login) loading screen goes black and never restores.

Will need more work.

David>
> [1] https://lore.kernel.org/linux-arm-msm/20260217-sdm845-hdk-v1-1-866f1965fef7@oss.qualcomm.com/

Re: [PATCH v2 5/5] arm64: dts: qcom: sdm845-xiaomi-beryllium-tianma: Disable MDSS

[Dmitry Baryshkov]

On Fri, Apr 10, 2026 at 03:51:12PM +0200, David Heidelberg wrote:
> On 18/03/2026 15:47, Dmitry Baryshkov wrote:
> > On Tue, Mar 17, 2026 at 11:12:35PM +0100, David Heidelberg via B4 Relay wrote:
> > > From: Petr Hodina <petr.hodina@protonmail.com>
> > > 
> > > Currently the panel driver for tianma is broken.
> > > Disable MDSS to prevent DRM taking over the framebuffer.
> > 
> > I'd still hope that somebody can get it to work. I'd start by using
> > prepare_prev_first. Sumit reported the panel as working in 2020 and I
> > have no doubts that it was the case. Another option migt be something
> > related to the dispcc (see my [1]).
> 
> Sadly, the prepare_prev_first didn't solve the issue. The framebuffer ->
> MDSS takover happens, but at greetd (login) loading screen goes black and
> never restores.
> 
> Will need more work.

Do you see a console _while_ it boots, after the handover? I'd check the
mode programming. Maybe, disabling panel reset would also (temporarily)
help.

> 
> David>
> > [1] https://lore.kernel.org/linux-arm-msm/20260217-sdm845-hdk-v1-1-866f1965fef7@oss.qualcomm.com/

-- 
With best wishes
Dmitry

Re: [PATCH v2 5/5] arm64: dts: qcom: sdm845-xiaomi-beryllium-tianma: Disable MDSS

[David Heidelberg]

On 12/04/2026 02:36, Dmitry Baryshkov wrote:
> On Fri, Apr 10, 2026 at 03:51:12PM +0200, David Heidelberg wrote:
>> On 18/03/2026 15:47, Dmitry Baryshkov wrote:
>>> On Tue, Mar 17, 2026 at 11:12:35PM +0100, David Heidelberg via B4 Relay wrote:
>>>> From: Petr Hodina <petr.hodina@protonmail.com>
>>>>
>>>> Currently the panel driver for tianma is broken.
>>>> Disable MDSS to prevent DRM taking over the framebuffer.
>>>
>>> I'd still hope that somebody can get it to work. I'd start by using
>>> prepare_prev_first. Sumit reported the panel as working in 2020 and I
>>> have no doubts that it was the case. Another option migt be something
>>> related to the dispcc (see my [1]).
>>
>> Sadly, the prepare_prev_first didn't solve the issue. The framebuffer ->
>> MDSS takover happens, but at greetd (login) loading screen goes black and
>> never restores.
>>
>> Will need more work.
> 
> Do you see a console _while_ it boots, after the handover? I'd check the
> mode programming. Maybe, disabling panel reset would also (temporarily)
> help.

When I get access to the phone for longer period of time I'll try to debug it 
step by step. This time I had only time to flash kernel and test if it boots 
with prepare_prev_first.

David

> 
>>
>> David>
>>> [1] https://lore.kernel.org/linux-arm-msm/20260217-sdm845-hdk-v1-1-866f1965fef7@oss.qualcomm.com/
> 

-- 
David Heidelberg