Re: [PATCH RFC 05/16] pmdomain: core: Support subdomains without pstate propagation

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] pmdomain: missing initial pstate propagation in genpd_add_subdomain()
--

commit 19c8f09b635c74bbdaf740eac823398c603b6fb4
Author: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

    pmdomain: core: Support subdomains without pstate propagation
    
    A subdomain may need its parent to be powered on without requiring its
    performance state to follow the child's. GenPD currently couples these
    requirements, so increasing the child's performance state can also
    raise the parent even when it only needs to remain on.

> diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
> index 76ff0d9a229c3..80ea70930cc63 100644
> --- a/drivers/pmdomain/core.c
> +++ b/drivers/pmdomain/core.c

[ ... ]

> @@ -2298,6 +2307,7 @@ static int genpd_add_subdomain(struct generic_pm_domain *genpd,
>  	}
>  
>  	link->parent = genpd;
> +	link->flags = flags;
>  	list_add_tail(&link->parent_node, &genpd->parent_links);
>  	link->child = subdomain;
>  	list_add_tail(&link->child_node, &subdomain->child_links);
>  	if (genpd_status_on_unlocked(subdomain))
>  		genpd_sd_counter_inc(genpd);

[Severity: High]
When the child domain is linked to the parent in genpd_add_subdomain(), its
power state is synced via genpd_sd_counter_inc(). However, if a consumer
device has already probed and set a performance state on the child domain
before it is linked (meaning it already has an active performance_state > 0),
does this code miss evaluating and propagating that initial performance state
to the parent?

If this initial propagation is omitted, the parent might operate at a lower
performance state than required by its subdomains. Could this lead to hardware
malfunctions or system crashes due to under-voltage or under-clocking?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261014-topic-qc_clk_dvfs-v1-0-3041b788e9f7@oss.qualcomm.com?part=5