linux-kernel - Re: [PATCH v6 2/2] PM / devfreq: mediatek: Introduce MediaTek CCI devfreq driver

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Message-ID: <e4d3ab91-9c53-79a0-76f8-098e6b846441@collabora.com>
Date:   Mon, 30 May 2022 14:16:31 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Johnson Wang <johnson.wang@...iatek.com>, cw00.choi@...sung.com,
        krzk+dt@...nel.org, robh+dt@...nel.org, kyungmin.park@...sung.com
Cc:     khilman@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, jia-wei.chang@...iatek.com,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v6 2/2] PM / devfreq: mediatek: Introduce MediaTek CCI
 devfreq driver

Il 27/05/22 13:00, Johnson Wang ha scritto:
> We introduce a devfreq driver for the MediaTek Cache Coherent Interconnect
> (CCI) used by some MediaTek SoCs.
> 
> In this driver, we use the passive devfreq driver to get target frequencies
> and adjust voltages accordingly. In MT8183 and MT8186, the MediaTek CCI
> is supplied by the same regulators with the little core CPUs.
> 
> Signed-off-by: Jia-Wei Chang <jia-wei.chang@...iatek.com>
> Signed-off-by: Johnson Wang <johnson.wang@...iatek.com>
> Acked-by: Chanwoo Choi <cw00.choi@...sung.com>
> ---
> This patch depends on "devfreq-testing"[1].
> [1]https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git/log/?h=devfreq-testing
> ---
>   drivers/devfreq/Kconfig           |  10 +
>   drivers/devfreq/Makefile          |   1 +
>   drivers/devfreq/mtk-cci-devfreq.c | 441 ++++++++++++++++++++++++++++++
>   3 files changed, 452 insertions(+)
>   create mode 100644 drivers/devfreq/mtk-cci-devfreq.c
> 
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index 87eb2b837e68..9754d8b31621 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -120,6 +120,16 @@ config ARM_TEGRA_DEVFREQ
>   	  It reads ACTMON counters of memory controllers and adjusts the
>   	  operating frequencies and voltages with OPP support.
>   
> +config ARM_MEDIATEK_CCI_DEVFREQ
> +	tristate "MEDIATEK CCI DEVFREQ Driver"
> +	depends on ARM_MEDIATEK_CPUFREQ || COMPILE_TEST
> +	select DEVFREQ_GOV_PASSIVE
> +	help
> +	  This adds a devfreq driver for MediaTek Cache Coherent Interconnect
> +	  which is shared the same regulators with the cpu cluster. It can track
> +	  buck voltages and update a proper CCI frequency. Use the notification
> +	  to get the regulator status.
> +
>   config ARM_RK3399_DMC_DEVFREQ
>   	tristate "ARM RK3399 DMC DEVFREQ Driver"
>   	depends on (ARCH_ROCKCHIP && HAVE_ARM_SMCCC) || \
> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
> index 0b6be92a25d9..bf40d04928d0 100644
> --- a/drivers/devfreq/Makefile
> +++ b/drivers/devfreq/Makefile
> @@ -11,6 +11,7 @@ obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
>   obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
>   obj-$(CONFIG_ARM_IMX_BUS_DEVFREQ)	+= imx-bus.o
>   obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ)	+= imx8m-ddrc.o
> +obj-$(CONFIG_ARM_MEDIATEK_CCI_DEVFREQ)	+= mtk-cci-devfreq.o
>   obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
>   obj-$(CONFIG_ARM_SUN8I_A33_MBUS_DEVFREQ)	+= sun8i-a33-mbus.o
>   obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra30-devfreq.o
> diff --git a/drivers/devfreq/mtk-cci-devfreq.c b/drivers/devfreq/mtk-cci-devfreq.c
> new file mode 100644
> index 000000000000..df42da35b312
> --- /dev/null
> +++ b/drivers/devfreq/mtk-cci-devfreq.c
> @@ -0,0 +1,441 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2022 MediaTek Inc.
> + */
> +

..snip..

> +};
> +
> +static int mtk_ccifreq_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct mtk_ccifreq_drv *drv;
> +	struct devfreq_passive_data *passive_data;
> +	struct dev_pm_opp *opp;
> +	unsigned long rate, opp_volt;
> +	int ret;
> +
> +	drv = devm_kzalloc(dev, sizeof(*drv), GFP_KERNEL);
> +	if (!drv)
> +		return -ENOMEM;
> +
> +	drv->dev = dev;
> +	drv->soc_data = (const struct mtk_ccifreq_platform_data *)
> +				of_device_get_match_data(&pdev->dev);
> +	mutex_init(&drv->reg_lock);
> +	platform_set_drvdata(pdev, drv);
> +
> +	drv->cci_clk = devm_clk_get(dev, "cci");
> +	if (IS_ERR(drv->cci_clk)) {
> +		ret = PTR_ERR(drv->cci_clk);
> +		return dev_err_probe(dev, ret,
> +				     "failed to get cci clk: %d\n", ret);
> +	}
> +
> +	drv->inter_clk = devm_clk_get(dev, "intermediate");
> +	if (IS_ERR(drv->inter_clk)) {
> +		ret = PTR_ERR(drv->inter_clk);
> +		return dev_err_probe(dev, ret,
> +				     "failed to get intermediate clk: %d\n", ret);
> +	}
> +
> +	drv->proc_reg = devm_regulator_get_optional(dev, "proc");

In the devicetree binding for this driver, the "proc" regulator is *not* optional,
but here you're using devm_regulator_get_optional.

If this is not optional, you should use devm_regulator_get() instead.

> +	if (IS_ERR(drv->proc_reg)) {
> +		ret = PTR_ERR(drv->proc_reg);
> +		return dev_err_probe(dev, ret,
> +				     "failed to get proc regulator: %d\n", ret);

There's no need to print ret... dev_err_probe() takes care of that for you already:
in this case, you're printing the value of ret twice.

> +	}
> +
> +	ret = regulator_enable(drv->proc_reg);

If you move this call after the devm_regulator_get_optional() call for the sram
vreg, you will be able to use dev_err_probe for the latter as well.

> +	if (ret) {
> +		dev_err(dev, "failed to enable proc regulator\n");

Why aren't you using dev_err_probe here, like you've done for the other instances?

> +		return ret;
> +	}
> +
> +	drv->sram_reg = devm_regulator_get_optional(dev, "sram");
> +	if (IS_ERR(drv->sram_reg))
> +		drv->sram_reg = NULL;

When you use regulator_get_optional() (including the devm_ variant of it), you
shall return an error, if there's any... that's what the _optional() is for.

if (IS_ERR(drv->sram_reg))
	return dev_err_probe(dev, PTR_ERR(drv->proc_reg),
			     "failed to get sram regulator");

> +	else {
> +		ret = regulator_enable(drv->sram_reg);
> +		if (ret) {
> +			dev_err(dev, "failed to enable sram regulator\n");
> +			goto out_free_resources;
> +		}
> +	}
> +

Regards,
Angelo