Re: [PATCH 2/3] Documentation: dt: binding: fsl: update property description for RCPM

[Li Yang]

On Mon, Sep 10, 2018 at 3:46 AM Ran Wang <ran.wang_1@xxxxxxx> wrote:
>
> Hi Scott,
>
> On 2018/9/8 4:23, Scott Wood wrote:
> >
> > On Fri, 2018-08-31 at 11:52 +0800, Ran Wang wrote:
> > > +Optional properties:
> > > + - big-endian : Indicate RCPM registers is big-endian. A RCPM node
> > > +   that doesn't have this property will be regarded as little-endian.
> >
> > You've just broken all the existing powerpc device trees that are big-endian
> > and have no big-endian property.
>
> Yes, powerpc RCPM driver (arch/powerpc/sysdev/fsl_rcpm.c) will not refer
> to big-endian. However, I think if Layerscape RCPM driver use different compatible
> id (such as ' fsl,qoriq-rcpm-2.2'), it might be safe. Is that OK?

For Layerscape Chassis(gen3) based chips, the Reference Manual named
the power management IP as COP_PMU instead of RCPM which makes sense
to me as the register map is also quite different from the reg map of
RCPM.  So I think it is reasonable to create a new binding and driver
for the Chassis Gen3 based PMU.  However, the
arch/powerpc/sysdev/fsl_rcpm.c driver probably should be moved to
drivers/soc/fsl, as the Gen2.x Chassis and RCPM IP are also used in
some non-PowerPC Layerscape SoCs.  From what I know, all the RCPM
based IP are all big endian, so there is no need to add this property
for the old binding.

>
> > > + - <property 'compatible' string of consumer device> : This string
> > > +   is referred by RCPM driver to judge if the consumer (such as flex timer)
> > > +   is able to be regards as wakeup source or not, such as
> > > + 'fsl,ls1012a-
> > > ftm'.
> > > +   Further, this property will carry the bit mask info to control
> > > +   coresponding wake up source.
> >
> > What will you do if there are multiple instances of a device with the same
> > compatible, and different wakeup bits?
>
> You got me! This is a problem in current version. Well, we have to decouple wake up
> source IP and RCPM driver. That's why I add a plat_pm driver to prevent wake up IP
> knowing any information of RCPM. So in current context, one idea come to me is to
> redesign property ' fsl,ls1012a-ftm = <0x20000>;', change to 'fsl,ls1012a-ftm = <&ftm0 0x20000>;'
> What do you say? And could you tell me which API I can use to check if that device's
> name is ftm0 (for example we want to find a node ftm0: ftm@29d000)?
>
> >Plus, it's an awkward design in
> > general, and you don't describe what the value actually means (bits in which
> > register?).
>
> Yes, I admit my design looks ugly and not flexible and extensible enough. However, for above reason,
> do you have any good idea, please? :)

Why do you have to move the wakeup information from device nodes to
the RCPM/PMU node?  For information related to both on-chip device and
SoC integration, the information normally goes into the node of
on-chip device instead of the integration IP's device node.  Existing
example like: interrupt, clock, memory map, and etc.  It is much
cleaner than listing all the interrupts in the interrupt controller's
node, right?

>
> As to the register information, I can explain here in details (will add to commit
> message of next version): There is a RCPM HW block which has register named IPPDEXPCR.
> It controls whether prevent certain IP (such as timer, usb, etc) from entering low
> power mode when system suspended. So it's necessary to program it if we want one
> of those IP work as a wakeup source. However, different Layerscape SoCs have different bit vs.
> IP mapping  layout. So I have to record this information in device tree and fetched by RCPM driver
> directly.
>
> Do I need to list all SoC's mapping information in this binding doc for reference?
>
> >What was wrong with the existing binding?
>
> There was one version of RCPM patch which requiring property 'fsl,#rcpm-wakeup-cells' but was not
> accepted by upstream finally. Now we will no need it any longer due to new design allow case of multiple
> RCPM devices existing case.
>
> >Alternatively, use the clock bindings.
>
> Sorry I didn't get your point.
>
> > > -
> > > -Example:
> > > -   lpuart0: serial@2950000 {
> > > -           compatible = "fsl,ls1021a-lpuart";
> > > -           reg = <0x0 0x2950000 0x0 0x1000>;
> > > -           interrupts = <GIC_SPI 80 IRQ_TYPE_LEVEL_HIGH>;
> > > -           clocks = <&sysclk>;
> > > -           clock-names = "ipg";
> > > -           fsl,rcpm-wakeup = <&rcpm 0x0 0x40000000>;
> > > +           big-endian;
> > > +           fsl,ls1012a-ftm = <0x20000>;
> > > +           fsl,pfe = <0xf0000020>;
> >
> > fsl,pfe is not documented.
>
> pfe patch is not upstream yet, will remove it.
>
> Regards,
> Ran
>
> > -Scott
>