On Fri, 19 Mar 2021 at 04:31, Aisheng Dong <aisheng.d...@nxp.com> wrote: > > Hi Ulf, > > > From: Ulf Hansson <ulf.hans...@linaro.org> > > Sent: Wednesday, March 17, 2021 5:31 PM > > > > Since the introduction of the PM domain support for the scu-pd, the genpd > > framework has been continuously improved. More preciously, using a single > > global power domain can quite easily be deployed for imx platforms. > > > > To avoid confusions, let's therefore make an update to the comments about > > the missing pieces. > > > > Signed-off-by: Ulf Hansson <ulf.hans...@linaro.org> > > Thanks for the update. > Reviewed-by: Dong Aisheng <aisheng.d...@nxp.com> > > BTW, I'm still uncertain if the new approach can finally work well for i.MX > as SCU PD > also supports multiple low power state. > I could investigate it more when I adding multi low power states support.
The multiple low power states are currently only supported per genpd and not per device. So, yes, in principle you could have one genpd per device as you currently model it, to support this. Although, thinking long term wise, we probably want something else that doesn't rely on the device to be attached to a genpd to support this use case. In the past, I have been talking to different people from various SoC vendors and it looks like the use case is there, but it's kind of messy to support it. I would certainly be very interested to hear about your use case, would you mind sharing some more about this? Moreover, note that, there is a limitation in the genpd infrastructure when you build a hierarchy with parent/childs genpds, when each genpd has multiple idle states. That is, a parent-genpd may be allowed to enter any of its idle states, no matter what idle state that has been selected for the child-genpd. As a matter of fact, I am about to fix this problem quite soon. Is perhaps this something that could be valuable for your platforms too? [...] Kind regards Uffe
