linux-kernel - Re: [PATCH v2 1/4] OPP: Allow required-opps even if the device doesn't have power-domains

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Date:   Tue, 16 Jul 2019 22:47:53 +0530
From:   Sibi Sankar <sibis@...eaurora.org>
To:     Saravana Kannan <saravanak@...gle.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     kernel-team@...roid.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] OPP: Allow required-opps even if the device
 doesn't have power-domains

Hey Saravana,
Thanks for taking time to post out this series.

On 6/26/19 3:03 AM, Saravana Kannan wrote:
> A Device-A can have a (minimum) performance requirement on another
> Device-B to be able to function correctly. This performance requirement
> on Device-B can also change based on the current performance level of
> Device-A.
> 
> The existing required-opps feature fits well to describe this need. So,
> instead of limiting required-opps to point to only PM-domain devices,
> allow it to point to any device.
> 
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
>   drivers/opp/core.c |  2 +-
>   drivers/opp/of.c   | 14 --------------
>   2 files changed, 1 insertion(+), 15 deletions(-)
> 
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index 0e7703fe733f..74c7bdc6f463 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -710,7 +710,7 @@ static int _set_required_opps(struct device *dev,
>   		return 0;
>   
>   	/* Single genpd case */
> -	if (!genpd_virt_devs) {
> +	if (!genpd_virt_devs && required_opp_tables[0]->is_genpd) {
https://patchwork.kernel.org/patch/10940671/
This was already removed as a part of ^^ and is in linux-next.

>   		pstate = opp->required_opps[0]->pstate;
>   		ret = dev_pm_genpd_set_performance_state(dev, pstate);
>   		if (ret) {
> diff --git a/drivers/opp/of.c b/drivers/opp/of.c
> index c10c782d15aa..7c8336e94aff 100644
> --- a/drivers/opp/of.c
> +++ b/drivers/opp/of.c
> @@ -195,9 +195,6 @@ static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
>   	 */
>   	count_pd = of_count_phandle_with_args(dev->of_node, "power-domains",
>   					      "#power-domain-cells");
> -	if (!count_pd)
> -		goto put_np;
> -
>   	if (count_pd > 1) {
>   		genpd_virt_devs = kcalloc(count, sizeof(*genpd_virt_devs),
>   					GFP_KERNEL);
> @@ -226,17 +223,6 @@ static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
>   
>   		if (IS_ERR(required_opp_tables[i]))
>   			goto free_required_tables;
> -
> -		/*
> -		 * We only support genpd's OPPs in the "required-opps" for now,
> -		 * as we don't know how much about other cases. Error out if the
> -		 * required OPP doesn't belong to a genpd.
> -		 */
> -		if (!required_opp_tables[i]->is_genpd) {
> -			dev_err(dev, "required-opp doesn't belong to genpd: %pOF\n",
> -				required_np);
> -			goto free_required_tables;
> -		}

I expect the series to not work as is in its current state since I
see a circular dependency here. The required-opp tables of the parent
devfreq won't be populated until we add the opp-table of the child
devfreq node while the child devfreq using passive governor would
return -EPROBE_DEFER until the parent devfreq probes.

The same applies to this patch -> https://patchwork.kernel.org/patch
/11046147/ I posted out based on your series. So we would probably have
to address the dependency here.

>   	}
>   
>   	goto put_np;
> 

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