Re: [PATCH] arm64: dts: qcom: sm8750-mtp: Set sufficient voltage for panel nt37801

[Bjorn Andersson <andersson@kernel.org>]

On Thu, Mar 26, 2026 at 03:06:52PM +0530, Ayushi Makhija wrote:
> On 3/24/2026 7:34 AM, Bjorn Andersson wrote:
> > On Mon, Mar 23, 2026 at 03:52:29PM +0530, Ayushi Makhija wrote:
> >> The NT37801 Sepc V1.0 chapter "5.7.1 Power On Sequence" states
> >> VDDI=1.65V~1.95V, so set sufficient voltage for panel nt37801.
> >>
> > 
> > Please add Fixes: tag.
> > 
> 
> Hi Bjorn,
> 
> Sure, will add in new patchset.
> 
> >> Signed-off-by: Ayushi Makhija <quic_amakhija@quicinc.com>
> > 
> > Please start using your oss.qualcomm.com address.
> > 
> >> ---
> >>  arch/arm64/boot/dts/qcom/sm8750-mtp.dts | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/arch/arm64/boot/dts/qcom/sm8750-mtp.dts b/arch/arm64/boot/dts/qcom/sm8750-mtp.dts
> >> index 3837f6785320..6ba4e69bf377 100644
> >> --- a/arch/arm64/boot/dts/qcom/sm8750-mtp.dts
> >> +++ b/arch/arm64/boot/dts/qcom/sm8750-mtp.dts
> >> @@ -462,7 +462,7 @@ vreg_l11b_1p0: ldo11 {
> >>  
> >>  		vreg_l12b_1p8: ldo12 {
> >>  			regulator-name = "vreg_l12b_1p8";
> >> -			regulator-min-microvolt = <1200000>;
> >> +			regulator-min-microvolt = <1650000>;
> > 
> > Are you sure it's not supposed to be 1.8V, given the name of the rail?
> > 
> > Regards,
> > Bjorn
> 
> There was already discussion regarding the minimum voltage for this regulator on sm8550 target
> on other upstream patch. 
> 
> Link: https://lore.kernel.org/all/aQQdQoCLeKhYtY7W@yuanjiey.ap.qualcomm.com/
> 
> This values is according to the NT37801 panel sec
> "The NT37801 Sepc V1.0 chapter "5.7.1 Power On Sequence" states 
> VDDI=1.65V~1.95V."
> 

Yes, so the panel requires 1.65V, so regulator-min-microvolt needs to be
at least that. But regulator-min-microvolt should account for all the
consumers of the rail, are there any others?

Which leads me to my question, the people designing the board named the
rail VREG_L12B_1P8 in the schematics, why didn't they name it
VREG_L12B_1P65?

Please check all the consumers and make the regulator-min-microvolt work
for all of them - if that's 1.65V, then your change is good.

Regards,
Bjorn

> Thanks,
> Ayushi
> 
> >>  			regulator-max-microvolt = <1800000>;
> >>  			regulator-initial-mode = <RPMH_REGULATOR_MODE_HPM>;
> >>  			regulator-allow-set-load;
> >> -- 
> >> 2.34.1
> >>
>