linux-kernel - Re: [PATCH 2/2] cpufreq: qcom-hw: Ensure only freq-domain regs are counted in num

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Message-ID: <7dec47af-0981-7d70-3926-69419f5d1c8e@linaro.org>
Date:   Thu, 12 Jan 2023 16:41:50 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bjorn Andersson <andersson@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, agross@...nel.org,
        krzysztof.kozlowski@...aro.org, marijn.suijten@...ainline.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Manivannan Sadhasivam <mani@...nel.org>,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] cpufreq: qcom-hw: Ensure only freq-domain regs are
 counted in num_domains



On 12.01.2023 16:37, Bjorn Andersson wrote:
> On Wed, Jan 11, 2023 at 09:51:25PM +0100, Konrad Dybcio wrote:
>> In preparation for CPRh-aware OSM programming, change the probe
>> function so that we determine the number of frequency domains by
>> counting the number of reg-names entries that begin with
>> "freq-domain", as the aforementioned changes require introduction
>> of non-freq-domain register spaces.
>>
> 
> Requiring reg-names would break backwards compatibility with at least
> sc7280 and sm6115.
Ouch, you're correct..

Does checking for reg-names and applying the code flow proposed in this
patch if found and the existing one if not sound good?

Konrad
> 
> Regards,
> Bjorn
> 
>> Fixes: 1a6a8b0080b0 ("cpufreq: qcom-hw: Fix reading "reg" with address/size-cells != 2")
>> Fixes: 054a3ef683a1 ("cpufreq: qcom-hw: Allocate qcom_cpufreq_data during probe")
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>> ---
>>  drivers/cpufreq/qcom-cpufreq-hw.c | 34 ++++++++++++++++++++++---------
>>  1 file changed, 24 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
>> index 9505a812d6a1..89d5ed267399 100644
>> --- a/drivers/cpufreq/qcom-cpufreq-hw.c
>> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
>> @@ -651,8 +651,9 @@ static int qcom_cpufreq_hw_driver_probe(struct platform_device *pdev)
>>  	struct device *dev = &pdev->dev;
>>  	struct device_node *soc_node;
>>  	struct device *cpu_dev;
>> +	const char *reg_name;
>>  	struct clk *clk;
>> -	int ret, i, num_domains, reg_sz;
>> +	int ret, i, num_reg_names, num_domains = 0;
>>  
>>  	clk = clk_get(dev, "xo");
>>  	if (IS_ERR(clk))
>> @@ -684,19 +685,32 @@ static int qcom_cpufreq_hw_driver_probe(struct platform_device *pdev)
>>  	if (!soc_node)
>>  		return -EINVAL;
>>  
>> -	ret = of_property_read_u32(soc_node, "#address-cells", &reg_sz);
>> -	if (ret)
>> +	num_reg_names = of_property_count_strings(dev->of_node, "reg-names");
>> +	if (num_reg_names <= 0) {
>> +		ret = num_reg_names ? num_reg_names : -ENODATA;
>>  		goto of_exit;
>> +	}
>>  
>> -	ret = of_property_read_u32(soc_node, "#size-cells", &i);
>> -	if (ret)
>> -		goto of_exit;
>> +	for (i = 0; i < num_reg_names; i++) {
>> +		ret = of_property_read_string_index(dev->of_node, "reg-names", i, &reg_name);
>> +		if (ret < 0)
>> +			goto of_exit;
>>  
>> -	reg_sz += i;
>> +		/*
>> +		 * Check if the i-th reg is a freq-domain base, no need to add 1
>> +		 * more byte for idx, as sizeof counts \0 whereas strlen does not.
>> +		 */
>> +		if (strlen(reg_name) == sizeof("freq-domain")) {
>> +			/* Check if this reg-name begins with "freq-domain" */
>> +			if (!strncmp(reg_name, "freq-domain", sizeof("freq-domain") - 1))
>> +				num_domains++;
>> +		}
>> +	}
>>  
>> -	num_domains = of_property_count_elems_of_size(dev->of_node, "reg", sizeof(u32) * reg_sz);
>> -	if (num_domains <= 0)
>> -		return num_domains;
>> +	if (num_domains <= 0) {
>> +		ret = -EINVAL;
>> +		goto of_exit;
>> +	}
>>  
>>  	qcom_cpufreq.data = devm_kzalloc(dev, sizeof(struct qcom_cpufreq_data) * num_domains,
>>  					 GFP_KERNEL);
>> -- 
>> 2.39.0
>>