[RFC PATCH 20/36] arm_mpam: Probe the hardware features resctrl supports

[Jonathan Cameron]

}
> >   
> > +/*
> > + * IHI009A.a has this nugget: "If a monitor does not support automatic behaviour
> > + * of NRDY, software can use this bit for any purpose" - so hardware might not
> > + * implement this - but it isn't RES0.
> > + *
> > + * Try and see what values stick in this bit. If we can write either value,
> > + * its probably not implemented by hardware.
> > + */
> > +#define mpam_ris_hw_probe_hw_nrdy(_ris, _mon_reg, _result)			\
> > +do {										\
> > +	u32 now;								\
> > +	u64 mon_sel;								\
> > +	bool can_set, can_clear;						\
> > +	struct mpam_msc *_msc = _ris->vmsc->msc;				\
> > +										\
> > +	if (WARN_ON_ONCE(!mpam_mon_sel_inner_lock(_msc))) {			\
> > +		_result = false;						\
> > +		break;								\
> > +	}									\
> > +	mon_sel = FIELD_PREP(MSMON_CFG_MON_SEL_MON_SEL, 0) |			\
> > +		  FIELD_PREP(MSMON_CFG_MON_SEL_RIS, _ris->ris_idx);		\
> > +	mpam_write_monsel_reg(_msc, CFG_MON_SEL, mon_sel);			\
> > +										\
> > +	mpam_write_monsel_reg(_msc, _mon_reg, MSMON___NRDY);			\
> > +	now = mpam_read_monsel_reg(_msc, _mon_reg);				\
> > +	can_set = now & MSMON___NRDY;						\
> > +										\
> > +	mpam_write_monsel_reg(_msc, _mon_reg, 0);				\
> > +	now = mpam_read_monsel_reg(_msc, _mon_reg);				\
> > +	can_clear = !(now & MSMON___NRDY);					\
> > +	mpam_mon_sel_inner_unlock(_msc);					\
> > +										\
> > +	_result = (!can_set || !can_clear);					\
> > +} while (0)  
> It is a bit surprising that something that looks like a function 
> modifies a boolean passed by value. Consider continuing the pattern you 
> have above:
> #define mpam_ris_hw_probe_hw_nrdy(_ris, _mon_reg, _result) 
> _mpam_ris_hw_probe_hw_nrdy(_ris, MSMON##_mon_reg, _result)
> 
> with signature:
> void _mpam_ris_hw_probe_hw_nrdy(struct mpam_msc *msc, u16 reg, bool 
> *hw_managed);
> 
> and using the _mpam functions from the new _mpam_ris_hw_probe_hw_nrdy().
> 

Agreed that this is ugly.  Only a tiny bit of macro stuff is actually going on here.
I'd make it function.

If you really want to construct MSMON_CSU etc then wrap that helper with
a macro that builds reg from the name.

I might have missed something though in converting this.
The version I have has some other changes though so not trivial to post here :(