[PATCH] [RFC] ARM: dts: imx6sx-sdb: Drop OPP hackery

[Leonard Crestez]

On Tue, 2017-04-25 at 21:30 +0200, Marek Vasut wrote:
> On 04/25/2017 06:42 PM, Marek Vasut wrote:
> > The imx6sx-sdb has one power supply that drives both VDDARM_IN
> > and VDDSOC_IN, which is the sw1a regulator on the PFUZE PMIC.
> > Connect both inputs to the sw1a regulator on the PMIC and drop
> > the OPP hackery which is no longer needed as the power framework
> > will take care of the regulator configuration as needed.
> > 
> > Signed-off-by: Marek Vasut <marex at denx.de>
> > Cc: Fabio Estevam <fabio.estevam at nxp.com>
> > Cc: Shawn Guo <shawnguo at kernel.org>
> 
> +CC Leonard

Tested-by: Leonard Crestez <leonard.crestez at nxp.com>

The OPP hack only applies to LDO bypass mode and that is not in
upstream. When LDOs are enabled the effect is to use higher voltages
than necessary for no good reason.

Setting these higher voltages can make some boards (for example Rev B)
fail to boot with ugly semi-random crashes reminiscent of memory
corruption. These failures happen the first time the lowest idle state
is used. This patch fixes those crashes.

It's not clear exactly why the crashes happen. Perhaps waking up from
idle draws more power than is available? I don't think it matters.

I sent a very similar patch a few minutes after this one:

http://lists.infradead.org/pipermail/linux-arm-kernel/2017-April/503241
.html

> > @@ -145,3 +128,11 @@
> >  		reg = <1>;
> >  	};
> >  };
> > +
> > +&reg_arm {
> > +	vin-supply = <&sw1a_reg>;
> > +};
> > +
> > +&reg_soc {
> > +	vin-supply = <&sw1a_reg>;
> > +};

This is also good, it will result in lower voltages will result in
lower voltages on VDD_ARM_SOC_IN rather than a fixed 1375 mV.

-- 
Regards,
Leonard