linux-kernel - Re: [PATCH v2 24/29] arm_mpam: Track bandwidth counter state for overflow and power management

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Message-ID: <20250912142419.00006c6d@huawei.com>
Date: Fri, 12 Sep 2025 14:24:19 +0100
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: James Morse <james.morse@....com>
CC: <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
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Subject: Re: [PATCH v2 24/29] arm_mpam: Track bandwidth counter state for
 overflow and power management

On Wed, 10 Sep 2025 20:43:04 +0000
James Morse <james.morse@....com> wrote:

> Bandwidth counters need to run continuously to correctly reflect the
> bandwidth.
> 
> The value read may be lower than the previous value read in the case
> of overflow and when the hardware is reset due to CPU hotplug.
> 
> Add struct mbwu_state to track the bandwidth counter to allow overflow
> and power management to be handled.
> 
> Signed-off-by: James Morse <james.morse@....com>
Trivial comment inline.  I haven't spent enough time thinking about this
to give a proper review so no tags yet.

Jonathan
 
> ---
> Changes since v1:
>  * Fixed lock/unlock typo.
> ---
>  drivers/resctrl/mpam_devices.c  | 154 +++++++++++++++++++++++++++++++-
>  drivers/resctrl/mpam_internal.h |  23 +++++
>  2 files changed, 175 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index 1543c33c5d6a..eeb62ed94520 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -918,6 +918,7 @@ static void gen_msmon_ctl_flt_vals(struct mon_read *m, u32 *ctl_val,
>  	*ctl_val |= MSMON_CFG_x_CTL_MATCH_PARTID;
>  
>  	*flt_val = FIELD_PREP(MSMON_CFG_x_FLT_PARTID, ctx->partid);
> +
Unrelated change.  If it makes sense figure out where to push it back to.

>  	if (m->ctx->match_pmg) {
>  		*ctl_val |= MSMON_CFG_x_CTL_MATCH_PMG;
>  		*flt_val |= FIELD_PREP(MSMON_CFG_x_FLT_PMG, ctx->pmg);