RE: [PATCH RESEND 2/5] ARM: dts: imx7d-sdb: Assign corresponding power supply for LDOs

[Anson Huang]

Hi, Leonard

> -----Original Message-----
> From: Leonard Crestez
> Sent: Wednesday, May 29, 2019 3:24 AM
> To: Anson Huang <anson.huang@xxxxxxx>
> Cc: robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx; shawnguo@xxxxxxxxxx;
> s.hauer@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>
> Subject: Re: [PATCH RESEND 2/5] ARM: dts: imx7d-sdb: Assign corresponding
> power supply for LDOs
> 
> On 12.05.2019 12:57, Anson Huang wrote:
> > On i.MX7D SDB board, sw2 supplies 1p0d/1p2 LDO, this patch assigns
> > corresponding power supply for 1p0d/1p2 LDO to avoid confusion by
> > below log:
> >
> > vdd1p0d: supplied by regulator-dummy
> > vdd1p2: supplied by regulator-dummy
> >
> > With this patch, the power supply is more accurate:
> >
> > vdd1p0d: supplied by SW2
> > vdd1p2: supplied by SW2
> >
> > diff --git a/arch/arm/boot/dts/imx7d-sdb.dts
> > b/arch/arm/boot/dts/imx7d-sdb.dts
> >
> > +&reg_1p0d {
> > +	vin-supply = <&sw2_reg>;
> > +};
> > +
> > +&reg_1p2 {
> > +	vin-supply = <&sw2_reg>;
> > +};
> 
> It's not clear why but this patch breaks imx7d-sdb boot. Checked two
> boards: in a board farm and on my desk.

Thanks for reporting this issue, I can reproduce it now, a quick debug shows
that with this patch, when setting reg_1p0d's voltage to 1.0V, the SW2's voltage
will be changed to 1.5V, the expected voltage should be 1.8V, so 1.5V cause board
reset. Below patch can fix this issue, but I am still checking if this is the best fix, once
I figure out, I will send out a fix patch for review:

+++ b/arch/arm/boot/dts/imx7d-sdb.dts
@@ -267,6 +267,7 @@
                                regulator-max-microvolt = <1850000>;
                                regulator-boot-on;
                                regulator-always-on;
+                               regulator-max-step-microvolt = <25000>;
                        };

Thanks,
Anson

> 
> --
> Regards,
> Leonard