linux-kernel - Re: [PATCH 2/2] cpufreq: brcmstb-avs-cpufreq: prefer SCMI cpufreq if supported

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Date:   Wed, 18 Apr 2018 09:37:17 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Markus Mayer <code@...yer.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Brian Norris <computersforpeace@...il.com>,
        Gregory Fong <gregory.0xf0@...il.com>
Cc:     Jim Quinlan <jim2101024@...il.com>,
        Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>,
        Power Management List <linux-pm@...r.kernel.org>,
        ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Markus Mayer <mmayer@...adcom.com>
Subject: Re: [PATCH 2/2] cpufreq: brcmstb-avs-cpufreq: prefer SCMI cpufreq if
 supported

On 04/18/2018 08:56 AM, Markus Mayer wrote:
> From: Jim Quinlan <jim2101024@...il.com>
> 
> If the SCMI cpufreq driver is supported, we bail, so that the new
> approach can be used.
> 
> Signed-off-by: Jim Quinlan <jim2101024@...il.com>
> Signed-off-by: Markus Mayer <mmayer@...adcom.com>
> ---
>  drivers/cpufreq/brcmstb-avs-cpufreq.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/cpufreq/brcmstb-avs-cpufreq.c b/drivers/cpufreq/brcmstb-avs-cpufreq.c
> index b07559b9ed99..b4861a730162 100644
> --- a/drivers/cpufreq/brcmstb-avs-cpufreq.c
> +++ b/drivers/cpufreq/brcmstb-avs-cpufreq.c
> @@ -164,6 +164,8 @@
>  #define BRCM_AVS_CPU_INTR	"brcm,avs-cpu-l2-intr"
>  #define BRCM_AVS_HOST_INTR	"sw_intr"
>  
> +#define ARM_SCMI_COMPAT		"arm,scmi"
> +
>  struct pmap {
>  	unsigned int mode;
>  	unsigned int p1;
> @@ -511,6 +513,20 @@ static int brcm_avs_prepare_init(struct platform_device *pdev)
>  	struct device *dev;
>  	int host_irq, ret;
>  
> +	/*
> +	 * If the SCMI cpufreq driver is supported, we bail, so that the more
> +	 * modern approach can be used.
> +	 */
> +	if (IS_ENABLED(CONFIG_ARM_SCMI_PROTOCOL)) {
> +		struct device_node *np;
> +
> +		np = of_find_compatible_node(NULL, NULL, ARM_SCMI_COMPAT);
> +		if (np) {
> +			of_node_put(np);
> +			return -ENXIO;
> +		}

We would probably want to make sure that the node is also enabled (that
is, does not have a status = "disabled" property) otherwise the check
can be defeated. Something like:

		if (np && of_device_is_available(np))

should be good for that.

Thanks!
-- 
Florian