Re: [PATCH 0/2] soc: imx: gpc: Power off PU domain in suspend/resume on 6qp

From: Lucas Stach
Date: Mon Jul 02 2018 - 09:58:37 EST

Am Montag, den 02.07.2018, 13:49 +0000 schrieb Leonard Crestez:
> On Mon, 2018-07-02 at 14:15 +0200, Lucas Stach wrote:
> > Am Montag, den 02.07.2018, 14:52 +0300 schrieb Leonard Crestez:
> > > With current code (even without my patches) attempting to dynamically
> > > remove/probe the GPC fils since since the per-pgc platform_device
> > > instances are not removed. I'm trying something like this:
> > >
> > > echo 130000.gpu > /sys/bus/platform/drivers/etnaviv-gpu/unbind
> > > echo 134000.gpu > /sys/bus/platform/drivers/etnaviv-gpu/unbind
> > > echo 20dc000.gpcÂÂ> /sys/bus/platform/drivers/imx-gpc/unbind
> > > echo 20dc000.gpcÂÂ> /sys/bus/platform/drivers/imx-gpc/bind
> > >
> > > But is there any usecase for dynamically removing the GPC? Instead of
> > > trying to fix it I'd rather delete imx_gpc_driver.remove, just like
> > > for gpcv2. Would anyone object to a patch doing this?
> >
> > Yes, as this is taking things in wrong direction. With device-links we
> > are able to unbind consumer devices when a provider is removed. As the
> > GPC is a consumer of a regulator, not having the ability to unbind it
> > would break that use case.
> The GPC is a "consumer" of the LDO regulators which are built into the
> SOC. Why would you want to unbind any of this stuff?

Which in turn might be consumers of external regulators, which may have
a module driver that can be reloaded by the user at will.

> I don't understand the usecase, maybe you can elaborate?

You could make that argument for almost every device on a SoC, yet the
explicit default in Linux is for device drivers to be hot-pluggable.

Anything that changes the system layout at Linux runtime, like
devicetree overlays or dynamic system partition solutions like
Jailhouse depend on driver/device hotplug to work. I know that there
are quite a few bugs in this area, because it's less tested than other
code paths, but I'm unwilling to accept that we are actively going in
the direction of breaking this stuff.