From: Petr Hodina <petr.hodina@protonmail.com>

Currently the panel driver for tianma is broken.
Disable MDSS to prevent DRM taking over the framebuffer.

Signed-off-by: Petr Hodina <petr.hodina@protonmail.com>
Signed-off-by: David Heidelberg <david@ixit.cz>
---
 arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts b/arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts
index b58964cde8342..d1c7bccaab500 100644
--- a/arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts
+++ b/arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts
@@ -36,3 +36,13 @@ touchscreen@1 {
 		touchscreen-size-y = <2246>;
 	};
 };
+
+&dispcc {
+	/* Disable for now so simple-framebuffer continues working */
+	status = "disabled";
+};
+
+&mdss {
+	/* Disable for now so simple-framebuffer continues working */
+	status = "disabled";
+};

-- 
2.53.0

On Wed, Mar 11, 2026 at 07:44:30PM +0100, David Heidelberg via B4 Relay wrote:
> From: Petr Hodina <petr.hodina@protonmail.com>
> 
> Currently the panel driver for tianma is broken.

How broken? Can it be fixed instead?

> Disable MDSS to prevent DRM taking over the framebuffer.
> 
> Signed-off-by: Petr Hodina <petr.hodina@protonmail.com>
> Signed-off-by: David Heidelberg <david@ixit.cz>
> ---
>  arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts b/arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts
> index b58964cde8342..d1c7bccaab500 100644
> --- a/arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts
> +++ b/arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts
> @@ -36,3 +36,13 @@ touchscreen@1 {
>  		touchscreen-size-y = <2246>;
>  	};
>  };
> +
> +&dispcc {
> +	/* Disable for now so simple-framebuffer continues working */
> +	status = "disabled";
> +};
> +
> +&mdss {
> +	/* Disable for now so simple-framebuffer continues working */
> +	status = "disabled";
> +};
> 
> -- 
> 2.53.0
> 
> 

-- 
With best wishes
Dmitry

On 12/03/2026 03:46, Dmitry Baryshkov wrote:
> On Wed, Mar 11, 2026 at 07:44:30PM +0100, David Heidelberg via B4 Relay wrote:
>> From: Petr Hodina <petr.hodina@protonmail.com>
>>
>> Currently the panel driver for tianma is broken.
> 
> How broken? Can it be fixed instead?

No output to the panel. Definitely can be fixed, but current situation is that 
we don't have anyone who has available time or device to tackle the problem.

I know it's not optimal, but on a way to achieve working mainline phones, my 
thinking is better to mark it as broken in mainline until someone fixes 
(assuming Fixes tag and backport) then just going black display (when we have at 
least framebuffer now).

David

> 
>> Disable MDSS to prevent DRM taking over the framebuffer.
>>
>> Signed-off-by: Petr Hodina <petr.hodina@protonmail.com>
>> Signed-off-by: David Heidelberg <david@ixit.cz>
>> ---
>>   arch/arm64/boot/dts/qcom/sdm845-xiaomi-beryllium-tianma.dts | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>

[...]

On 3/12/26 12:25 PM, David Heidelberg wrote:
> On 12/03/2026 03:46, Dmitry Baryshkov wrote:
>> On Wed, Mar 11, 2026 at 07:44:30PM +0100, David Heidelberg via B4 Relay wrote:
>>> From: Petr Hodina <petr.hodina@protonmail.com>
>>>
>>> Currently the panel driver for tianma is broken.
>>
>> How broken? Can it be fixed instead?
> 
> No output to the panel. Definitely can be fixed, but current situation is that we don't have anyone who has available time or device to tackle the problem.
> 
> I know it's not optimal, but on a way to achieve working mainline phones, my thinking is better to mark it as broken in mainline until someone fixes (assuming Fixes tag and backport) then just going black display (when we have at least framebuffer now).

If you have a person with limited time, would simply copying this:

2b973ca48ff3 ("drm/panel: sony-td4353-jdi: Enable prepare_prev_first")

fix it?

Konrad

On 13/03/2026 13:38, Konrad Dybcio wrote:
> On 3/12/26 12:25 PM, David Heidelberg wrote:
>> On 12/03/2026 03:46, Dmitry Baryshkov wrote:
>>> On Wed, Mar 11, 2026 at 07:44:30PM +0100, David Heidelberg via B4 Relay wrote:
>>>> From: Petr Hodina <petr.hodina@protonmail.com>
>>>>
>>>> Currently the panel driver for tianma is broken.
>>>
>>> How broken? Can it be fixed instead?
>>
>> No output to the panel. Definitely can be fixed, but current situation is that we don't have anyone who has available time or device to tackle the problem.
>>
>> I know it's not optimal, but on a way to achieve working mainline phones, my thinking is better to mark it as broken in mainline until someone fixes (assuming Fixes tag and backport) then just going black display (when we have at least framebuffer now).
> 
> If you have a person with limited time, would simply copying this:
> 
> 2b973ca48ff3 ("drm/panel: sony-td4353-jdi: Enable prepare_prev_first")

Sorry, I don't follow. You meant introducing prepare_prev_first?

I asked if it's possible to test, but looking at the rest of the driver, it'll 
need refactor anyway.

David>
> fix it?
> 
> Konrad

-- 
David Heidelberg

On 3/13/26 2:09 PM, David Heidelberg wrote:
> On 13/03/2026 13:38, Konrad Dybcio wrote:
>> On 3/12/26 12:25 PM, David Heidelberg wrote:
>>> On 12/03/2026 03:46, Dmitry Baryshkov wrote:
>>>> On Wed, Mar 11, 2026 at 07:44:30PM +0100, David Heidelberg via B4 Relay wrote:
>>>>> From: Petr Hodina <petr.hodina@protonmail.com>
>>>>>
>>>>> Currently the panel driver for tianma is broken.
>>>>
>>>> How broken? Can it be fixed instead?
>>>
>>> No output to the panel. Definitely can be fixed, but current situation is that we don't have anyone who has available time or device to tackle the problem.
>>>
>>> I know it's not optimal, but on a way to achieve working mainline phones, my thinking is better to mark it as broken in mainline until someone fixes (assuming Fixes tag and backport) then just going black display (when we have at least framebuffer now).
>>
>> If you have a person with limited time, would simply copying this:
>>
>> 2b973ca48ff3 ("drm/panel: sony-td4353-jdi: Enable prepare_prev_first")
> 
> Sorry, I don't follow. You meant introducing prepare_prev_first?

Yes, just setting that single flag

> I asked if it's possible to test, but looking at the rest of the driver, it'll need refactor anyway.

Well I'dve assumed it worked at least at some point in time given it's
in mainline?

Konrad

On 16/03/2026 10:30, Konrad Dybcio wrote:
> On 3/13/26 2:09 PM, David Heidelberg wrote:
>> On 13/03/2026 13:38, Konrad Dybcio wrote:
>>> On 3/12/26 12:25 PM, David Heidelberg wrote:
>>>> On 12/03/2026 03:46, Dmitry Baryshkov wrote:
>>>>> On Wed, Mar 11, 2026 at 07:44:30PM +0100, David Heidelberg via B4 Relay wrote:
>>>>>> From: Petr Hodina <petr.hodina@protonmail.com>
>>>>>>
>>>>>> Currently the panel driver for tianma is broken.
>>>>>
>>>>> How broken? Can it be fixed instead?
>>>>
>>>> No output to the panel. Definitely can be fixed, but current situation is that we don't have anyone who has available time or device to tackle the problem.
>>>>
>>>> I know it's not optimal, but on a way to achieve working mainline phones, my thinking is better to mark it as broken in mainline until someone fixes (assuming Fixes tag and backport) then just going black display (when we have at least framebuffer now).
>>>
>>> If you have a person with limited time, would simply copying this:
>>>
>>> 2b973ca48ff3 ("drm/panel: sony-td4353-jdi: Enable prepare_prev_first")
>>
>> Sorry, I don't follow. You meant introducing prepare_prev_first?
> 
> Yes, just setting that single flag
> 
>> I asked if it's possible to test, but looking at the rest of the driver, it'll need refactor anyway.
> 
> Well I'dve assumed it worked at least at some point in time given it's
> in mainline?

That's not sure, for previous panel drivers (OP6/6T) upstreamed drivers didn't 
worked on mainline at all.

Trying prepare_prev_first could work thou. Hopefully Petr will be able to give 
it a shot.

David

> 
> Konrad

-- 
David Heidelberg