Re: [PATCH 4/4] arm64: dts: qcom: sm7225-fairphone-fp4: Wire up PM6150L LCDB

["Luca Weiss" <luca.weiss@fairphone.com>]

On Fri Nov 13, 2026 at 2:09 PM CET, Val Packett wrote:
>
> On 11/13/26 9:59 AM, Luca Weiss wrote:
>> On Fri Nov 13, 2026 at 9:16 AM CET, Luca Weiss wrote:
>>> Since Linux has gained LCDB support now, wire up the LCDB regulators so
>>> we can turn them off and on as desired.
>> Actually after some more testing with extra patches, it seems that on
>> FP4 the touchscreen stays dead after toggling the lcdb regulator, while
>> on FP3 it works perfectly fine.
>>
>> So please ignore this specific patch for now, I will figure out what the
>> problem is and re-submit. All the other patches in the series are still
>> good to go in!
>
> Your touchscreen needs to be a drm panel follower and/or reference the 
> same supplies as well :) Most modern touch controllers are part of the 
> same physical DDIC as the actual display side

Yep, I assumed the same. Probably need to resend the init sequence [0]
after power cycle, when the panel is back on again, to get everything
running again.

[0] https://lore.kernel.org/linux-arm-msm/20260821-fp4-hx83112a-v1-2-474941bd8860@fairphone.com/ hx83112a_init()

Fairphone 3 should be a similar setup (FP3: hx83112b, FP4: hx83112a) but
apparently the hx83112b doesn't need any sort of init to start sending
touch inputs compared to hx83112a.

Regards
Luca