linux-kernel - Re: [PATCH v2 09/15] powercap/intel_rapl: Cleanup Power Limits support

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Message-ID: <2b936d88a51ca62d29a15c4b04265c5ae2e7352f.camel@intel.com>
Date:   Wed, 6 Sep 2023 15:32:12 +0000
From:   "Pandruvada, Srinivas" <srinivas.pandruvada@...el.com>
To:     "Zhang, Rui" <rui.zhang@...el.com>,
        "ville.syrjala@...ux.intel.com" <ville.syrjala@...ux.intel.com>
CC:     "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 09/15] powercap/intel_rapl: Cleanup Power Limits
 support

On Wed, 2023-09-06 at 03:14 +0000, Zhang, Rui wrote:
> Hi, Ville,
> 
> 
[...]

> The below change keeps the previous logic, can you confirm this?
> 
> IMO, the new logic is right because making any change to a 
> locked power limit is meaningless.
> 
> Srinivas,
> 
> Do we check if a domain/power_limit is locked before we enabling it
> in
> thermald?
There is no way to check locked bit from user space.

This was an issue several years back and thermald added logic to avoid
trying.
"
             if (ret == -ENODATA) {
                        thd_log_info("powercap RAPL is BIOS locked,
cannot update\n");
                        bios_locked = true;
}
"

But here it seems that issue with suspend/resume. thermald doesn't do
anything during suspend/resume.

Thanks,
Srinivas

> 
> thanks,
> rui
> 
> diff --git a/drivers/powercap/intel_rapl_common.c
> b/drivers/powercap/intel_rapl_common.c
> index 5c2e6d5eea2a..f6816a91d027 100644
> --- a/drivers/powercap/intel_rapl_common.c
> +++ b/drivers/powercap/intel_rapl_common.c
> @@ -893,7 +893,7 @@ static int rapl_write_pl_data(struct rapl_domain
> *rd, int pl,
>         if (!is_pl_valid(rd, pl))
>                 return -EINVAL;
>  
> -       if (rd->rpl[pl].locked) {
> +       if (rd->rpl[pl].locked && pl_prim == PL_LIMIT) {
>                 pr_warn("%s:%s:%s locked by BIOS\n", rd->rp->name,
> rd-
> > name, pl_names[pl]);
>                 return -EACCES;
>         }
> 
> 
> 
> 
>