linux-kernel - Re: [PATCH 3/7] OPP: Rework _set_required_devs() to manage a single device per call

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Date: Wed, 26 Jun 2024 12:03:21 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
	Stephen Boyd <sboyd@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Nikunj Kela <nkela@...cinc.com>,
	Prasad Sodagudi <psodagud@...cinc.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Jonathan Hunter <jonathanh@...dia.com>, linux-pm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] OPP: Rework _set_required_devs() to manage a single
 device per call

On 19-06-24, 16:08, Ulf Hansson wrote:
> @@ -2494,36 +2495,68 @@ static int _opp_set_required_devs(struct opp_table *opp_table,
>  		return -EINVAL;
>  	}
>  
> -	/* Another device that shares the OPP table has set the required devs ? */
> -	if (opp_table->required_devs[0])
> -		return 0;
> +	/* Genpd core takes care of propagation to parent genpd */
> +	if (opp_table->is_genpd) {

A genpd can have non-genpd devices in the required OPPs and so this
isn't sufficient. What we were ignoring earlier was genpd having
another genpd as required opp.

> +		dev_err(dev, "%s: Operation not supported for genpds\n", __func__);
> +		return -EOPNOTSUPP;
> +	}
>  
>  	for (i = 0; i < opp_table->required_opp_count; i++) {
> -		/* Genpd core takes care of propagation to parent genpd */
> -		if (required_devs[i] && opp_table->is_genpd &&
> -		    opp_table->required_opp_tables[i]->is_genpd) {
> -			dev_err(dev, "%s: Operation not supported for genpds\n", __func__);
> -			return -EOPNOTSUPP;
> -		}
> +		struct opp_table *table = opp_table->required_opp_tables[i];
> +
> +		/*
> +		 * The OPP table should be available at this point. If not, it's
> +		 * not the one we are looking for.
> +		 */
> +		if (IS_ERR(table))
> +			continue;
> +
> +		/* Move to the next available index. */
> +		if (opp_table->required_devs[i])
> +			continue;
>  
> -		opp_table->required_devs[i] = required_devs[i];
> +		/*
> +		 * We need to compare the nodes for the OPP tables, rather than
> +		 * the OPP tables themselves, as we may have separate instances.
> +		 */
> +		if (required_opp_table->np == table->np) {
> +

We don't keep such empty lines in OPP core generally at this place.

> +			/* Cross check the OPP tables and fix it if needed. */

Copy the bigger comment from_opp_attach_genpd() here too. It helps
understanding why required_opp_tables entry is getting replaced.

> +			if (required_opp_table != table) {
> +				dev_pm_opp_put_opp_table(table);
> +				_get_opp_table_kref(required_opp_table);
> +				opp_table->required_opp_tables[i] = required_opp_table;
> +			}
> +
> +			opp_table->required_devs[i] = required_dev;
> +
> +			/*
> +			 * Add the required_dev as a user of the OPP table, so
> +			 * we can call dev_pm_opp_set_opp() on it directly.
> +			 */
> +			if (!_add_opp_dev(required_dev, required_opp_table)) {
> +				dev_err(dev, "Failed to add the device to the required OPP table\n");
> +				return -ENOMEM;
> +			}
> +
> +			return i;
> +		}
>  	}

-- 
viresh