Re: [RFC PATCH 30/36] arm_mpam: Add mpam_msmon_read() to read monitor value

[Ben Horgan <ben.horgan@arm.com>]

Hi James,

On 7/11/25 19:36, James Morse wrote:
> Reaing a monitor involves configuring what you want to monitor, and
nit: s/Reaing/Reading/
> reading the value. Components made up of multiple MSC may need values
> from each MSC. MSCs may take time to configure, returning 'not ready'.
> The maximum 'not ready' time should have been provided by firmware.
> 
> Add mpam_msmon_read() to hide all this. If (one of) the MSC returns
> not ready, then wait the full timeout value before trying again.
> 
> CC: Shanker Donthineni <sdonthineni@nvidia.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
>   drivers/platform/arm64/mpam/mpam_devices.c  | 222 ++++++++++++++++++++
>   drivers/platform/arm64/mpam/mpam_internal.h |  18 ++
>   2 files changed, 240 insertions(+)
> 
> diff --git a/drivers/platform/arm64/mpam/mpam_devices.c b/drivers/platform/arm64/mpam/mpam_devices.c
> index b11503d8ef1b..7d2d2929b292 100644
> --- a/drivers/platform/arm64/mpam/mpam_devices.c
> +++ b/drivers/platform/arm64/mpam/mpam_devices.c
> @@ -960,6 +960,228 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
>   	return 0;
>   }
>   
> +struct mon_read {
> +	struct mpam_msc_ris		*ris;
> +	struct mon_cfg			*ctx;
> +	enum mpam_device_features	type;
> +	u64				*val;
> +	int				err;
> +};
> +
> +static void gen_msmon_ctl_flt_vals(struct mon_read *m, u32 *ctl_val,
> +				   u32 *flt_val)
> +{
> +	struct mon_cfg *ctx = m->ctx;
> +
> +	switch (m->type) {
> +	case mpam_feat_msmon_csu:
> +		*ctl_val = MSMON_CFG_MBWU_CTL_TYPE_CSU;
> +		break;
> +	case mpam_feat_msmon_mbwu:
> +		*ctl_val = MSMON_CFG_MBWU_CTL_TYPE_MBWU;
> +		break;
> +	default:
> +		return;
> +	}
> +
> +	/*
> +	 * For CSU counters its implementation-defined what happens when not
> +	 * filtering by partid.
> +	 */
> +	*ctl_val |= MSMON_CFG_x_CTL_MATCH_PARTID;
> +
> +	*flt_val = FIELD_PREP(MSMON_CFG_MBWU_FLT_PARTID, ctx->partid);
> +	if (m->ctx->match_pmg) {
> +		*ctl_val |= MSMON_CFG_x_CTL_MATCH_PMG;
> +		*flt_val |= FIELD_PREP(MSMON_CFG_MBWU_FLT_PMG, ctx->pmg);
> +	}
> +
> +	if (mpam_has_feature(mpam_feat_msmon_mbwu_rwbw, &m->ris->props))
> +		*flt_val |= FIELD_PREP(MSMON_CFG_MBWU_FLT_RWBW, ctx->opts);
> +}
> +
> +static void read_msmon_ctl_flt_vals(struct mon_read *m, u32 *ctl_val,
> +				    u32 *flt_val)
> +{
> +	struct mpam_msc *msc = m->ris->vmsc->msc;
> +
> +	switch (m->type) {
> +	case mpam_feat_msmon_csu:
> +		*ctl_val = mpam_read_monsel_reg(msc, CFG_CSU_CTL);
> +		*flt_val = mpam_read_monsel_reg(msc, CFG_CSU_FLT);
> +		break;
> +	case mpam_feat_msmon_mbwu:
> +		*ctl_val = mpam_read_monsel_reg(msc, CFG_MBWU_CTL);
> +		*flt_val = mpam_read_monsel_reg(msc, CFG_MBWU_FLT);
> +		break;
> +	default:
> +		return;
> +	}
> +}
> +
> +/* Remove values set by the hardware to prevent aparant mismatches. */
> +static void clean_msmon_ctl_val(u32 *cur_ctl)
> +{
> +	*cur_ctl &= ~MSMON_CFG_x_CTL_OFLOW_STATUS;
> +}
> +
> +static void write_msmon_ctl_flt_vals(struct mon_read *m, u32 ctl_val,
> +				     u32 flt_val)
> +{
> +	struct mpam_msc *msc = m->ris->vmsc->msc;
> +
> +	/*
> +	 * Write the ctl_val with the enable bit cleared, reset the counter,
> +	 * then enable counter.
> +	 */
> +	switch (m->type) {
> +	case mpam_feat_msmon_csu:
> +		mpam_write_monsel_reg(msc, CFG_CSU_FLT, flt_val);
> +		mpam_write_monsel_reg(msc, CFG_CSU_CTL, ctl_val);
> +		mpam_write_monsel_reg(msc, CSU, 0);
> +		mpam_write_monsel_reg(msc, CFG_CSU_CTL, ctl_val | MSMON_CFG_x_CTL_EN);
> +		break;
> +	case mpam_feat_msmon_mbwu:
> +		mpam_write_monsel_reg(msc, CFG_MBWU_FLT, flt_val);
> +		mpam_write_monsel_reg(msc, CFG_MBWU_CTL, ctl_val);
> +		mpam_write_monsel_reg(msc, MBWU, 0);
> +		mpam_write_monsel_reg(msc, CFG_MBWU_CTL, ctl_val | MSMON_CFG_x_CTL_EN);
> +		break;
> +	default:
> +		return;
> +	}
> +}
> +
> +/* Call with MSC lock held */
> +static void __ris_msmon_read(void *arg)
> +{
> +	u64 now;
> +	bool nrdy = false;
> +	struct mon_read *m = arg;
> +	struct mon_cfg *ctx = m->ctx;
> +	struct mpam_msc_ris *ris = m->ris;
> +	struct mpam_props *rprops = &ris->props;
> +	struct mpam_msc *msc = m->ris->vmsc->msc;
> +	u32 mon_sel, ctl_val, flt_val, cur_ctl, cur_flt;
> +
> +	if (!mpam_mon_sel_inner_lock(msc)) {
> +		m->err = -EIO;
> +		return;
> +	}
> +	mon_sel = FIELD_PREP(MSMON_CFG_MON_SEL_MON_SEL, ctx->mon) |
> +		  FIELD_PREP(MSMON_CFG_MON_SEL_RIS, ris->ris_idx);
> +	mpam_write_monsel_reg(msc, CFG_MON_SEL, mon_sel);
> +
> +	/*
> +	 * Read the existing configuration to avoid re-writing the same values.
> +	 * This saves waiting for 'nrdy' on subsequent reads.
> +	 */
> +	read_msmon_ctl_flt_vals(m, &cur_ctl, &cur_flt);
> +	clean_msmon_ctl_val(&cur_ctl);
> +	gen_msmon_ctl_flt_vals(m, &ctl_val, &flt_val);
> +	if (cur_flt != flt_val || cur_ctl != (ctl_val | MSMON_CFG_x_CTL_EN))
> +		write_msmon_ctl_flt_vals(m, ctl_val, flt_val);
> +
> +	switch (m->type) {
> +	case mpam_feat_msmon_csu:
> +		now = mpam_read_monsel_reg(msc, CSU);
> +		if (mpam_has_feature(mpam_feat_msmon_csu_hw_nrdy, rprops))
> +			nrdy = now & MSMON___NRDY;
> +		break;
> +	case mpam_feat_msmon_mbwu:
> +		now = mpam_read_monsel_reg(msc, MBWU);
> +		if (mpam_has_feature(mpam_feat_msmon_mbwu_hw_nrdy, rprops))
> +			nrdy = now & MSMON___NRDY;
> +		break;
> +	default:
> +		m->err = -EINVAL;
> +		break;
> +	}
> +	mpam_mon_sel_inner_unlock(msc);
> +
> +	if (nrdy) {
> +		m->err = -EBUSY;
> +		return;
> +	}
> +
> +	now = FIELD_GET(MSMON___VALUE, now);
> +	*m->val += now;
> +}
> +
> +static int _msmon_read(struct mpam_component *comp, struct mon_read *arg)
> +{
> +	int err, idx;
> +	struct mpam_msc *msc;
> +	struct mpam_vmsc *vmsc;
> +	struct mpam_msc_ris *ris;
> +
> +	idx = srcu_read_lock(&mpam_srcu);
> +	list_for_each_entry_rcu(vmsc, &comp->vmsc, comp_list) {
> +		msc = vmsc->msc;
> +
> +		mpam_mon_sel_outer_lock(msc);
> +		list_for_each_entry_rcu(ris, &vmsc->ris, vmsc_list) {
> +			arg->ris = ris;
> +
> +			err = smp_call_function_any(&msc->accessibility,
> +						    __ris_msmon_read, arg,
> +						    true);
> +			if (!err && arg->err)
> +				err = arg->err;
> +			if (err)
> +				break;
> +		}
> +		mpam_mon_sel_outer_unlock(msc);
> +		if (err)
> +			break;
> +	}
> +	srcu_read_unlock(&mpam_srcu, idx);
> +
> +	return err;
> +}
> +
> +int mpam_msmon_read(struct mpam_component *comp, struct mon_cfg *ctx,
> +		    enum mpam_device_features type, u64 *val)
> +{
> +	int err;
> +	struct mon_read arg;
> +	u64 wait_jiffies = 0;
> +	struct mpam_props *cprops = &comp->class->props;
> +
> +	might_sleep();
> +
> +	if (!mpam_is_enabled())
> +		return -EIO;
> +
> +	if (!mpam_has_feature(type, cprops))
> +		return -EOPNOTSUPP;
> +
> +	memset(&arg, 0, sizeof(arg));
> +	arg.ctx = ctx;
> +	arg.type = type;
> +	arg.val = val;
> +	*val = 0;
> +
> +	err = _msmon_read(comp, &arg);
> +	if (err == -EBUSY && comp->class->nrdy_usec)
> +		wait_jiffies = usecs_to_jiffies(comp->class->nrdy_usec);
> +
> +	while (wait_jiffies)
> +		wait_jiffies = schedule_timeout_uninterruptible(wait_jiffies);
> +
> +	if (err == -EBUSY) {
> +		memset(&arg, 0, sizeof(arg));
> +		arg.ctx = ctx;
> +		arg.type = type;
> +		arg.val = val;
> +		*val = 0;
> +
> +		err = _msmon_read(comp, &arg);
> +	}
> +
> +	return err;
> +}
> +
>   static void mpam_reset_msc_bitmap(struct mpam_msc *msc, u16 reg, u16 wd)
>   {
>   	u32 num_words, msb;
> diff --git a/drivers/platform/arm64/mpam/mpam_internal.h b/drivers/platform/arm64/mpam/mpam_internal.h
> index aca91f7dfbf6..4aabef96fb7a 100644
> --- a/drivers/platform/arm64/mpam/mpam_internal.h
> +++ b/drivers/platform/arm64/mpam/mpam_internal.h
> @@ -308,6 +308,21 @@ struct mpam_msc_ris {
>   	struct mpam_garbage	garbage;
>   };
>   
> +/* The values for MSMON_CFG_MBWU_FLT.RWBW */
> +enum mon_filter_options {
> +	COUNT_BOTH	= 0,
> +	COUNT_WRITE	= 1,
> +	COUNT_READ	= 2,
> +};
> +
> +struct mon_cfg {
> +	u16                     mon;
> +	u8                      pmg;
> +	bool                    match_pmg;
> +	u32                     partid;
> +	enum mon_filter_options opts;
> +};
> +
>   static inline int mpam_alloc_csu_mon(struct mpam_class *class)
>   {
>   	struct mpam_props *cprops = &class->props;
> @@ -360,6 +375,9 @@ void mpam_disable(struct work_struct *work);
>   int mpam_apply_config(struct mpam_component *comp, u16 partid,
>   		      struct mpam_config *cfg);
>   
> +int mpam_msmon_read(struct mpam_component *comp, struct mon_cfg *ctx,
> +		    enum mpam_device_features, u64 *val);
> +
>   int mpam_get_cpumask_from_cache_id(unsigned long cache_id, u32 cache_level,
>   				   cpumask_t *affinity);
>   

-- 
Thanks,

Ben