linux-kernel - Re: [PATCH 5/8] OPP: Allow multiple clocks for a device

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Date:   Thu, 30 Jun 2022 14:39:43 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/8] OPP: Allow multiple clocks for a device

On 30/06/2022 14:32, Krzysztof Kozlowski wrote:
> On 10/06/2022 10:20, Viresh Kumar wrote:
>> This patch adds support to allow multiple clocks for a device.
>>
>> The design is pretty much similar to how this is done for regulators,
>> and platforms can supply their own version of the config_clks() callback
>> if they have multiple clocks for their device. The core manages the
>> calls via opp_table->config_clks() eventually.
>>
>> We have kept both "clk" and "clks" fields in the OPP table structure and
>> the reason is provided as a comment in _opp_set_clknames(). The same
>> isn't done for "rates" though and we use rates[0] at most of the places
>> now.
>>
>> Co-developed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> 
> (...)
> 
>> +	rates = kmalloc_array(count, sizeof(*rates), GFP_KERNEL);
>> +	if (!rates)
>> +		return -ENOMEM;
>> +
>> +	ret = of_property_read_u64_array(np, "opp-hz", rates, count);
>> +	if (ret) {
>> +		pr_err("%s: Error parsing opp-hz: %d\n", __func__, ret);
>> +	} else {
>> +		/*
>> +		 * Rate is defined as an unsigned long in clk API, and so
>> +		 * casting explicitly to its type. Must be fixed once rate is 64
>> +		 * bit guaranteed in clk API.
>> +		 */
>> +		for (i = 0; i < count; i++) {
>> +			new_opp->rates[i] = (unsigned long)rates[i];
>> +
>> +			/* This will happen for frequencies > 4.29 GHz */
>> +			WARN_ON(new_opp->rates[i] != rates[i]);
>> +		}
>> +	}
>> +
>> +	kfree(rates);
>> +
>> +	return ret;
>> +}
>> +
>>  static int _read_bw(struct dev_pm_opp *new_opp, struct opp_table *opp_table,
>>  		    struct device_node *np, bool peak)
>>  {
>> @@ -812,19 +859,13 @@ static int _read_opp_key(struct dev_pm_opp *new_opp,
>>  			 struct opp_table *opp_table, struct device_node *np)
>>  {
>>  	bool found = false;
>> -	u64 rate;
>>  	int ret;
>>  
>> -	ret = of_property_read_u64(np, "opp-hz", &rate);
>> -	if (!ret) {
>> -		/*
>> -		 * Rate is defined as an unsigned long in clk API, and so
>> -		 * casting explicitly to its type. Must be fixed once rate is 64
>> -		 * bit guaranteed in clk API.
>> -		 */
>> -		new_opp->rate = (unsigned long)rate;
>> +	ret = _read_rate(new_opp, opp_table, np);
>> +	if (ret)
>> +		return ret;
>> +	else if (opp_table->clk_count == 1)
> 
> Shouldn't this be >=1? I got several clocks and this one fails.

Actually this might be correct, but you need to update the bindings. Now
you require opp-level for case with multiple clocks.

Best regards,
Krzysztof