Re: [PATCH 3/4] arm64: dts: qcom: sdm845: Add missing MDSS reset

[David Heidelberg <david@ixit.cz>]

On 18/02/2026 13:19, Dmitry Baryshkov wrote:
> On Wed, Feb 18, 2026 at 12:18:39PM +0100, David Heidelberg wrote:
>> On 18/02/2026 11:30, Konrad Dybcio wrote:
>>> On 2/17/26 10:20 PM, Dmitry Baryshkov wrote:
>>>> From: David Heidelberg <david@ixit.cz>
>>>>
>>>> If the OS does not support recovering the state left by the
>>>> bootloader it needs a way to reset display hardware, so that it can
>>>> start from a clean state. Add a reference to the relevant reset.
>>>
>>> This is not the relevant reset
>>>
>>> You want MDSS_CORE_BCR @ 0xaf0_2000
>>
>> Thanks, I prepared the fixes [1].
> 
> UPD: touching that register resets the device. So, it seems, we will
> have to live without the MDSS Core reset of SDM845.

For me, so far, one test on Pixel 3 it freezes the device. Haven't found 
UART dongle, so not sure where exactly.

David

> 
>>
>> I'll try to test it if it's not breaking anything for us and send as v2 of
>> [2].
>>
>> David
>>
>> [1] https://codeberg.org/sdm845/linux/commits/branch/b4/mdss-reset
>> [2] https://patchwork.kernel.org/project/linux-arm-msm/patch/20260112-mdss-reset-v1-1-af7c572204d3@ixit.cz/
>>
>>>
>>> Konrad
>>>
>>>>
>>>> Signed-off-by: David Heidelberg <david@ixit.cz>
>>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
>>>> ---
>>>
>>>
>>>>    arch/arm64/boot/dts/qcom/sdm845.dtsi | 1 +
>>>>    1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/arch/arm64/boot/dts/qcom/sdm845.dtsi b/arch/arm64/boot/dts/qcom/sdm845.dtsi
>>>> index bf2f9c04adba..75c192eddc57 100644
>>>> --- a/arch/arm64/boot/dts/qcom/sdm845.dtsi
>>>> +++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi
>>>> @@ -4550,6 +4550,7 @@ mdss: display-subsystem@ae00000 {
>>>>    			reg-names = "mdss";
>>>>    			power-domains = <&dispcc MDSS_GDSC>;
>>>> +			resets = <&dispcc DISP_CC_MDSS_RSCC_BCR>;
>>>>    			clocks = <&dispcc DISP_CC_MDSS_AHB_CLK>,
>>>>    				 <&dispcc DISP_CC_MDSS_MDP_CLK>;
>>>>
>>
>> -- 
>> David Heidelberg
>>
> 

-- 
David Heidelberg