Re: [PATCH 0/9] Add Reset Controller support for Actions Semi Owl SoCs

Manivannan Sadhasivam
2018-08-08T17:30:05Z

Hi Rob,

On Tue, Aug 07, 2018 at 12:47:10PM -0600, Rob Herring wrote:
> On Mon, Jul 30, 2018 at 08:41:31PM +0530, Manivannan Sadhasivam wrote:
> > Hi Andreas,
> >
> > On Mon, Jul 30, 2018 at 12:26:07PM +0200, Andreas Färber wrote:
> > > Hi Mani,
> > >
> > > Am 27.07.2018 um 20:45 schrieb Manivannan Sadhasivam:
> > > > This patchset adds Reset Controller (RMU) support for Actions Semi
> > > > Owl SoCs, S900 and S700. For the Owl SoCs, RMU has been integrated into
> > > > the clock subsystem in hardware. Hence, in software we integrate RMU
> > > > support into common clock driver inorder to maintain compatibility.
> > >
> > > Can this not be placed into drivers/reset/ by using mfd-simple with a
> > > sub-node in DT?
>
> That is exactly what I tell folks not to do. Design the DT based on h/w
> blocks, not current desired driver split for some OS.
>
> > Actually I was not sure where to place this reset controller driver. When I
> > looked into other similar ones such as sunxi, they just integrated into the
> > clk subsystem. So I just chose that path. But yeah, this is hacky!
> >
> > But this RMU is not MFD by any means. Since the CMU (Clock) and RMU (Reset)
> > are two separate IPs inside SoC, we shouldn't describe it as a MFD driver. Since
> > RMU has only 2 registers, the HW designers decided to use up the CMU memory
> > map. So, maybe syscon would be best option I think. What is your opinion?
>
> If there's nothing shared then it is not a syscon. If you can create
> separate address ranges, then 2 nodes is probably okay. If the registers
> are all mixed up, then 1 node.
>

I don't quite understand the reason for not being syscon. The definition
of syscon says that, "System controller node represents a register region
containing a set of miscellaneous registers. The registers are not cohesive
enough to represent as any specific type of device." which exactly fits
this case. Only the registers of CMU & RMU are shared and not the HW block!

Can you please clarify?

Thanks,
Mani

> Rob