linux-kernel - Re: [PATCH V2 13/15] cpufreq: mediatek: Link CCI device to CPU

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Date:   Fri, 8 Apr 2022 15:37:08 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Rex-BC Chen <rex-bc.chen@...iatek.com>, rafael@...nel.org,
        viresh.kumar@...aro.org, robh+dt@...nel.org, krzk+dt@...nel.org
Cc:     matthias.bgg@...il.com, jia-wei.chang@...iatek.com,
        roger.lu@...iatek.com, hsinyi@...gle.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
Subject: Re: [PATCH V2 13/15] cpufreq: mediatek: Link CCI device to CPU

Il 08/04/22 06:59, Rex-BC Chen ha scritto:
> From: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> 
> In some MediaTek SoCs, like MT8183, CPU and CCI share the same power
> supplies. Cpufreq needs to check if CCI devfreq exists and wait until
> CCI devfreq ready before scaling frequency.
> 
> - Add is_ccifreq_ready() to link CCI device to CPI, and CPU will start
>    DVFS when CCI is ready.
> - Add platform data for MT8183.
> 
> Signed-off-by: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> ---
>   drivers/cpufreq/mediatek-cpufreq.c | 69 +++++++++++++++++++++++++++++-
>   1 file changed, 68 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/mediatek-cpufreq.c b/drivers/cpufreq/mediatek-cpufreq.c
> index b08ab7c14818..cebe5af2ef5d 100644
> --- a/drivers/cpufreq/mediatek-cpufreq.c
> +++ b/drivers/cpufreq/mediatek-cpufreq.c
> @@ -22,6 +22,7 @@ struct mtk_cpufreq_platform_data {
>   	int proc_max_volt;
>   	int sram_min_volt;
>   	int sram_max_volt;
> +	bool is_ccifreq_support;

bool ccifreq_supported; looks better.

>   };
>   
>   /*
> @@ -38,6 +39,7 @@ struct mtk_cpufreq_platform_data {
>   struct mtk_cpu_dvfs_info {
>   	struct cpumask cpus;
>   	struct device *cpu_dev;
> +	struct device *cci_dev;
>   	struct regulator *proc_reg;
>   	struct regulator *sram_reg;
>   	struct clk *cpu_clk;
> @@ -52,6 +54,7 @@ struct mtk_cpu_dvfs_info {
>   	int opp_cpu;
>   	unsigned long opp_freq;
>   	const struct mtk_cpufreq_platform_data *soc_data;
> +	bool is_ccifreq_bounded;

bool ccifreq_bound; looks better.

>   };
>   
>   static struct platform_device *cpufreq_pdev;
> @@ -171,6 +174,29 @@ static int mtk_cpufreq_set_voltage(struct mtk_cpu_dvfs_info *info, int vproc)
>   	return ret;
>   }
>   
> +static bool is_ccifreq_ready(struct mtk_cpu_dvfs_info *info)
> +{
> +	struct device_link *sup_link;
> +
> +	if (info->is_ccifreq_bounded)
> +		return true;
> +
> +	sup_link = device_link_add(info->cpu_dev, info->cci_dev,
> +				   DL_FLAG_AUTOREMOVE_CONSUMER);
> +	if (!sup_link) {
> +		dev_err(info->cpu_dev, "cpu%d: sup_link is NULL\n",
> +			info->opp_cpu);

Please, don't break this line: 84 columns are ok.

> +		return false;
> +	}
> +
> +	if (sup_link->supplier->links.status != DL_DEV_DRIVER_BOUND)
> +		return false;
> +
> +	info->is_ccifreq_bounded = true;
> +
> +	return true;
> +}
> +
>   static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
>   				  unsigned int index)
>   {
> @@ -183,6 +209,9 @@ static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
>   	long freq_hz, old_freq_hz;
>   	int vproc, old_vproc, inter_vproc, target_vproc, ret;
>   
> +	if (info->soc_data->is_ccifreq_support && !is_ccifreq_ready(info))
> +		return 0;

Honestly, I think that pretending that everything is alright and faking
set_target success is *not* a good idea...

You should return -EAGAIN here, not zero.

Regards,
Angelo