Re: [PATCH v7 07/11] arm_mpam: propagate MSC access errors for mpam_reprogram_ris_partid()

[Srivathsa L Rao <srivathsa.rao@oss.qualcomm.com>]

Hi Andre,

mpam_reprogram_ris_partid() writes hardware registers sequentially.
If a write fails midway (possible on PCC MSCs via SCMI), the earlier
writes are already committed and the hardware is left in a partially
configured state.
Currently this is safe only because mpam_fb_disable_mpam() tears
everything down on any firmware error. If that behavior is ever
relaxed (e.g. for transient BUSY handling), a partial state could
persist and produce weird behavior?

I wanted to point this as a design note.


On 7/31/2026 10:33 PM, Andre Przywara wrote:
> Allow the mpam_reprogram_ris_partid() function check for and return
> errors, and propagate MSC read and write errors from the lower level up.
> This also covers the callers of this function: mpam_reset_ris() and
> apply_config().
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>   drivers/resctrl/mpam_devices.c | 136 ++++++++++++++++++++++-----------
>   1 file changed, 93 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index 38450c55e45e..32088ad1d67e 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -1601,7 +1601,7 @@ void mpam_msmon_reset_mbwu(struct mpam_component *comp, struct mon_cfg *ctx)
>   	}
>   }
>   ...

> +static int mpam_reprogram_ris_partid(struct mpam_msc_ris *ris, u16 partid,
> +				     struct mpam_config *cfg)
>   {
>   	u32 pri_val = 0;
>   	..
> -	mutex_unlock(&msc->part_sel_lock);
> +	return 0;
>   }
>   
--

Best Regards,
Srivathsa