[PATCH 10/33] arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate

[James Morse]

Hi Ben,

On 01/09/2025 10:11, Ben Horgan wrote:
> On 8/22/25 16:29, James Morse wrote:
>> Probing MPAM is convoluted. MSCs that are integrated with a CPU may
>> only be accessible from those CPUs, and they may not be online.
>> Touching the hardware early is pointless as MPAM can't be used until
>> the system-wide common values for num_partid and num_pmg have been
>> discovered.
>>
>> Start with driver probe/remove and mapping the MSC.

>> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
>> new file mode 100644
>> index 000000000000..07e0f240eaca
>> --- /dev/null
>> +++ b/drivers/resctrl/mpam_internal.h
>> @@ -0,0 +1,62 @@

>> +struct mpam_msc {
>> +	/* member of mpam_all_msc */
>> +	struct list_head        glbl_list;
>> +
>> +	int			id;
>> +	struct platform_device *pdev;
>> +
>> +	/* Not modified after mpam_is_enabled() becomes true */
>> +	enum mpam_msc_iface	iface;
>> +	u32			pcc_subspace_id;
>> +	struct mbox_client	pcc_cl;
>> +	struct pcc_mbox_chan	*pcc_chan;
>> +	u32			nrdy_usec;
>> +	cpumask_t		accessibility;
>> +
>> +	/*
>> +	 * probe_lock is only take during discovery. After discovery these
>> +	 * properties become read-only and the lists are protected by SRCU.
>> +	 */
>> +	struct mutex		probe_lock;
>> +	unsigned long		ris_idxs[128 / BITS_PER_LONG];

> Why is this sized this way? RIS_MAX is 4 bits and so there are at most
> 16 RIS per msc.

Hmmm, lost in time - I agree with the 16 reasoning. Fixed.
(It's likely due to RES0 space above the field - but that has been filled in with other
 stuff since then. RIS was added as a 'backward compatible feature' - I was wary of them
 extending it)


>> +	u32			ris_max;
>> +
>> +	/* mpam_msc_ris of this component */
>> +	struct list_head	ris;
>> +
>> +	/*
>> +	 * part_sel_lock protects access to the MSC hardware registers that are
>> +	 * affected by MPAMCFG_PART_SEL. (including the ID registers that vary
>> +	 * by RIS).
>> +	 * If needed, take msc->lock first.
>> +	 */
>> +	struct mutex		part_sel_lock;
>> +
>> +	/*
>> +	 * mon_sel_lock protects access to the MSC hardware registers that are
>> +	 * affeted by MPAMCFG_MON_SEL.
>> +	 * If needed, take msc->lock first.
>> +	 */
>> +	struct mutex		outer_mon_sel_lock;
>> +	raw_spinlock_t		inner_mon_sel_lock;
>> +	unsigned long		inner_mon_sel_flags;
>> +
>> +	void __iomem		*mapped_hwpage;
>> +	size_t			mapped_hwpage_sz;
>> +};
>> +
>> +#endif /* MPAM_INTERNAL_H */

Thanks,

James