linux-kernel - Re: [PATCH V4 05/14] cpufreq: mediatek: Add opp notification support

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Date:   Mon, 25 Apr 2022 10:50:26 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rex-BC Chen <rex-bc.chen@...iatek.com>
Cc:     rafael@...nel.org, robh+dt@...nel.org, krzk+dt@...nel.org,
        matthias.bgg@...il.com, jia-wei.chang@...iatek.com,
        roger.lu@...iatek.com, hsinyi@...gle.com, khilman@...libre.com,
        angelogioacchino.delregno@...labora.com, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com,
        "Andrew-sh.Cheng" <andrew-sh.cheng@...iatek.com>
Subject: Re: [PATCH V4 05/14] cpufreq: mediatek: Add opp notification support

On 22-04-22, 15:52, Rex-BC Chen wrote:
> From: "Andrew-sh.Cheng" <andrew-sh.cheng@...iatek.com>
> 
> >From this opp notifier, cpufreq should listen to opp notification and do

Why the extra ">" here ?

> proper actions when receiving events of disable and voltage adjustment.
> 
> One of the user for this opp notifier is MediaTek SVS.
> The MediaTek Smart Voltage Scaling (SVS) is a hardware which calculates
> suitable SVS bank voltages to OPP voltage table.
> 
> Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng@...iatek.com>
> Signed-off-by: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> Signed-off-by: Rex-BC Chen <rex-bc.chen@...iatek.com>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---
>  drivers/cpufreq/mediatek-cpufreq.c | 92 +++++++++++++++++++++++++++---
>  1 file changed, 84 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/cpufreq/mediatek-cpufreq.c b/drivers/cpufreq/mediatek-cpufreq.c
> +static int mtk_cpufreq_opp_notifier(struct notifier_block *nb,
> +				    unsigned long event, void *data)
> +{
> +	struct dev_pm_opp *opp = data;
> +	struct dev_pm_opp *new_opp;
> +	struct mtk_cpu_dvfs_info *info;
> +	unsigned long freq, volt;
> +	struct cpufreq_policy *policy;
> +	int ret = 0;
> +
> +	info = container_of(nb, struct mtk_cpu_dvfs_info, opp_nb);
> +
> +	if (event == OPP_EVENT_ADJUST_VOLTAGE) {

I don't see any call to dev_pm_opp_adjust_voltage() for your platform, how is
this ever going to get called ?

> +		freq = dev_pm_opp_get_freq(opp);
> +
> +		mutex_lock(&info->reg_lock);
> +		if (info->opp_freq == freq) {
> +			volt = dev_pm_opp_get_voltage(opp);
> +			ret = mtk_cpufreq_set_voltage(info, volt);
> +			if (ret)
> +				dev_err(info->cpu_dev,
> +					"failed to scale voltage: %d\n", ret);
> +		}
> +		mutex_unlock(&info->reg_lock);
> +	} else if (event == OPP_EVENT_DISABLE) {
> +		freq = dev_pm_opp_get_freq(opp);
> +
> +		/* case of current opp item is disabled */
> +		if (info->opp_freq == freq) {
> +			freq = 1;
> +			new_opp = dev_pm_opp_find_freq_ceil(info->cpu_dev,
> +							    &freq);
> +			if (IS_ERR(new_opp)) {
> +				dev_err(info->cpu_dev,
> +					"all opp items are disabled\n");
> +				ret = PTR_ERR(new_opp);
> +				return notifier_from_errno(ret);
> +			}
> +
> +			dev_pm_opp_put(new_opp);
> +			policy = cpufreq_cpu_get(info->opp_cpu);
> +			if (policy) {
> +				cpufreq_driver_target(policy, freq / 1000,
> +						      CPUFREQ_RELATION_L);
> +				cpufreq_cpu_put(policy);

IIUC, then you are trying to change the frequency if a currently used OPP is
getting removed ? In that case, this problem is generic enough not to be fixed
in a end driver. This should be fixed in core somehow.

-- 
viresh