RE: [PATCH v1] ARM: dts: imx6sl-evk: keep sw4 always on
From: Anson Huang
Date: Tue Jul 03 2018 - 03:44:21 EST
> -----Original Message-----
> From: Shawn Guo [mailto:shawnguo@xxxxxxxxxx]
> Sent: Tuesday, July 3, 2018 1:39 PM
> To: Robin Gong <yibin.gong@xxxxxxx>
> Cc: festevam@xxxxxxxxx; Anson Huang <anson.huang@xxxxxxx>;
> mark.rutland@xxxxxxx; devicetree@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx; dl-linux-imx
> <linux-imx@xxxxxxx>; kernel@xxxxxxxxxxxxxx; Fabio Estevam
> <fabio.estevam@xxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v1] ARM: dts: imx6sl-evk: keep sw4 always on
> On Mon, Jul 02, 2018 at 02:12:52AM +0000, Robin Gong wrote:
> > But in fact, the original dts is not correct without
> > 'regulator-always- on'since SW4 is the critical DDR power rail,
> > although, it's kept on in the previous kernel by no switches
> > enable/disable interfaces provided in pfuze driver. Adding new
> > property which can be done totally by the common 'regulator-always-on'
> > is not a good choice. Keep the dts patch adding 'regulator-always-on'
> > ahead of pfuze driver pach adding enable/disable interface is enough for such
> case I think.
> We can not just break the installed DTBs like this. If patching regulator driver
> with a new property is really difficult, we could migrate the existing users in a
> 'soft' way:
Patching regulator driver needs to add property for those regulators can be OFF,
it will make users confuse with original regulator framework knowledge, NOT a
> - Add required regulator-always-on for regulator nodes in DTS.
I & Yibin already sent out patch to add " regulator-always-on " for regulator nodes in DTS,
so they can be applied first?
> - Patch i.MX platform code to check the presence of regulator-always-on
> property for critical regulators, and give a big warning if it's
It is NOT easy to identify which switch is critical or NOT, and different platforms
have different board design, it will introduce many platform specified code, so I think
just revert the pfuze100 switch enable/disable patch should be OK for now.
> - Wait for a couple of release cycles for users to migrate.
> - Add regulator driver patch back and break users who keep ignoring
> the warning.
After a couple of release cycles, add the pfuze100 switch enable/disable patch
back to support this feature, I believe users should switch to new dtb with "regulator-always-on"