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

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Message-ID: <20230112153704.6d37dygm4yfexdq6@builder.lan>
Date:   Thu, 12 Jan 2023 09:37:04 -0600
From:   Bjorn Andersson <andersson@...nel.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.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 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.

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
>