Re: [PATCH v7 4/8] devfreq: add mediatek cci devfreq

andrew-sh.cheng
2020-07-10T06:54:51Z

On Fri, 2020-07-10 at 10:31 +0800, Andrew-sh.Cheng wrote:
> From: "Andrew-sh.Cheng" <andrew-sh.cheng@mediatek.com>
>
> This adds a devfreq driver for the Cache Coherent Interconnect (CCI)
> of the Mediatek MT8183.
>

Hi Chanwoo Choi~
Due to my mail system crash, I couldn't find your mail to reply your
suggestion at patch version-6.
I reply at here.

> On the MT8183 the CCI is supplied by the same regulator as the LITTLE
> cores. The driver is notified when the regulator voltage changes
> (driven by cpufreq) and adjusts the CCI frequency to the maximum
> possible value.
>
> Change-Id: I3d54ede336418e76df5d316064b6c3857a9f1075
> Signed-off-by: Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>
> ---
> drivers/devfreq/Kconfig | 10 ++
> drivers/devfreq/Makefile | 1 +
> drivers/devfreq/mt8183-cci-devfreq.c | 198 +++++++++++++++++++++++++++++++++++
> 3 files changed, 209 insertions(+)
> create mode 100644 drivers/devfreq/mt8183-cci-devfreq.c
>
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index 42b1286e98e6..109aab7ea45b 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -111,6 +111,16 @@ config ARM_IMX8M_DDRC_DEVFREQ
> This adds the DEVFREQ driver for the i.MX8M DDR Controller. It allows
> adjusting DRAM frequency.
>
> +config ARM_MT8183_CCI_DEVFREQ
> + tristate "MT8183 CCI DEVFREQ Driver"
> + depends on ARM_MEDIATEK_CPUFREQ
> + help
> + This adds a devfreq driver for Cache Coherent Interconnect
> + of Mediatek MT8183, which is shared the same regulator
> + with cpu cluster.
> + It can track buck voltage and update a proper CCI frequency.
> + Use notification to get regulator status.
> +
> config ARM_TEGRA_DEVFREQ
> tristate "NVIDIA Tegra30/114/124/210 DEVFREQ Driver"
> depends on ARCH_TEGRA_3x_SOC || ARCH_TEGRA_114_SOC || \
> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
> index 3ca1ad0ecb97..78733ff6fa5d 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-$(CONFIG_ARM_MT8183_CCI_DEVFREQ) += mt8183-cci-devfreq.o
> obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ) += rk3399_dmc.o
> obj-$(CONFIG_ARM_TEGRA_DEVFREQ) += tegra30-devfreq.o
> obj-$(CONFIG_ARM_TEGRA20_DEVFREQ) += tegra20-devfreq.o
> diff --git a/drivers/devfreq/mt8183-cci-devfreq.c b/drivers/devfreq/mt8183-cci-devfreq.c
> new file mode 100644
> index 000000000000..62d02464a34b
> --- /dev/null
> +++ b/drivers/devfreq/mt8183-cci-devfreq.c
> @@ -0,0 +1,198 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2019 MediaTek Inc.
> +
> + * Author: Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/devfreq.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/time.h>
> +
> +#define MAX_VOLT_LIMIT (1150000)
> +
> +struct cci_devfreq {
> + struct devfreq *devfreq;
> + struct regulator *cpu_reg;
> + struct clk *cci_clk;
> + int old_vproc;
> + unsigned long old_freq;
> +};
> +
> +static int mtk_cci_set_voltage(struct cci_devfreq *cci_df, int vproc)
> +{
> + int ret;
> +
> + ret = regulator_set_voltage(cci_df->cpu_reg, vproc,
> + MAX_VOLT_LIMIT);
> + if (!ret)
> + cci_df->old_vproc = vproc;
> + return ret;
> +}
> +
> +static int mtk_cci_devfreq_target(struct device *dev, unsigned long *freq,
> + u32 flags)
> +{
> + int ret;
> + struct cci_devfreq *cci_df = dev_get_drvdata(dev);
> + struct dev_pm_opp *opp;
> + unsigned long opp_rate, opp_voltage, old_voltage;
> +
> + if (!cci_df)
> + return -EINVAL;
> +
> + if (cci_df->old_freq == *freq)
> + return 0;
> +
> + opp_rate = *freq;
> + opp = devfreq_recommended_opp(dev, &opp_rate, 1);
> + opp_voltage = dev_pm_opp_get_voltage(opp);
> + dev_pm_opp_put(opp);
> +
> + old_voltage = cci_df->old_vproc;
> + if (old_voltage == 0)
> + old_voltage = regulator_get_voltage(cci_df->cpu_reg);
> +
> + // scale up: set voltage first then freq
> + if (opp_voltage > old_voltage) {
> + ret = mtk_cci_set_voltage(cci_df, opp_voltage);
> + if (ret) {
> + pr_err("cci: failed to scale up voltage\n");
> + return ret;
> + }
> + }
> +
> + ret = clk_set_rate(cci_df->cci_clk, *freq);
> + if (ret) {
> + pr_err("%s: failed cci to set rate: %d\n", __func__,
> + ret);
> + mtk_cci_set_voltage(cci_df, old_voltage);
> + return ret;
> + }
> +
> + // scale down: set freq first then voltage
> + if (opp_voltage < old_voltage) {
> + ret = mtk_cci_set_voltage(cci_df, opp_voltage);
> + if (ret) {
> + pr_err("cci: failed to scale down voltage\n");
> + clk_set_rate(cci_df->cci_clk, cci_df->old_freq);
> + return ret;
> + }
> + }
> +

When notified by OPP_EVENT_ADJUST_VOLTAGE, I need to set voltage, even
the freqeuncy not chagne.
I didn't use dev_pm_opp_set_regulators() and dev_pm_opp_set_rate() to
change cci ratio at this version.

> + cci_df->old_freq = *freq;
> +
> + return 0;
> +}
> +
> +static struct devfreq_dev_profile cci_devfreq_profile = {
> + .target = mtk_cci_devfreq_target,

I didn't add .exit to do dev_pm_opp_of_remove_table(), this will be
called at driver.remove.

> +};
> +
> +static int mtk_cci_devfreq_probe(struct platform_device *pdev)
> +{
> + struct device *cci_dev = &pdev->dev;
> + struct cci_devfreq *cci_df;
> + struct devfreq_passive_data *passive_data;
> + int ret;
> +
> + cci_df = devm_kzalloc(cci_dev, sizeof(*cci_df), GFP_KERNEL);
> + if (!cci_df)
> + return -ENOMEM;
> +
> + cci_df->cci_clk = devm_clk_get(cci_dev, "cci_clock");
> + ret = PTR_ERR_OR_ZERO(cci_df->cci_clk);
> + if (ret) {
> + if (ret != -EPROBE_DEFER)
> + dev_err(cci_dev, "failed to get clock for CCI: %d\n",
> + ret);
> + return ret;
> + }
> + cci_df->cpu_reg = devm_regulator_get_optional(cci_dev, "proc");
> + ret = PTR_ERR_OR_ZERO(cci_df->cpu_reg);
> + if (ret) {
> + if (ret != -EPROBE_DEFER)
> + dev_err(cci_dev, "failed to get regulator for CCI: %d\n",
> + ret);
> + return ret;
> + }
> + ret = regulator_enable(cci_df->cpu_reg);
> + if (ret) {
> + dev_err(cci_dev, "enable buck for cci fail\n");
> + return ret;
> + }
> +
> + ret = dev_pm_opp_of_add_table(cci_dev);
> + if (ret) {
> + dev_err(cci_dev, "Fail to get OPP table for CCI: %d\n", ret);
> + return ret;
> + }
> +
> + platform_set_drvdata(pdev, cci_df);
> +
> + passive_data = devm_kzalloc(cci_dev, sizeof(*passive_data), GFP_KERNEL);
> + if (!passive_data) {
> + ret = -ENOMEM;
> + goto err_opp;
> + }
> +
> + passive_data->parent_type = CPUFREQ_PARENT_DEV;
> +
> + cci_df->devfreq = devm_devfreq_add_device(cci_dev,
> + &cci_devfreq_profile,
> + DEVFREQ_GOV_PASSIVE,
> + passive_data);
> + if (IS_ERR(cci_df->devfreq)) {
> + ret = PTR_ERR(cci_df->devfreq);
> + dev_err(cci_dev, "cannot create cci devfreq device:%d\n", ret);
> + goto err_opp;
> + }
> +
> + return 0;
> +
> +err_opp:
> + dev_pm_opp_of_remove_table(cci_dev);
> + return ret;
> +}
> +
> +static int mtk_cci_devfreq_remove(struct platform_device *pdev)
> +{
> + struct device *cci_dev = &pdev->dev;
> + struct cci_devfreq *cci_df;
> + struct notifier_block *opp_nb;
> +
> + cci_df = platform_get_drvdata(pdev);
> + opp_nb = &cci_df->opp_nb;
> +
> + dev_pm_opp_unregister_notifier(cci_dev, opp_nb);

I understand what you mean when I type this reply...
I will move it to to patch "cci devfreq register opp notification for
SVS support" next time.

> + dev_pm_opp_of_remove_table(cci_dev);
> + regulator_disable(cci_df->cpu_reg);
> +
> + return 0;
> +}
> +
> +static const __maybe_unused struct of_device_id
> + mediatek_cci_of_match[] = {

Actually, I don't quite understand when to us __maybe_unused
This is a suggestion from patch version 2.
https://patchwork.kernel.org/patch/10876449/
Please give me some advice.
Thank you.

> + { .compatible = "mediatek,mt8183-cci" },
> + { },
> +};
> +MODULE_DEVICE_TABLE(of, mediatek_cci_of_match);
> +
> +static struct platform_driver cci_devfreq_driver = {
> + .probe = mtk_cci_devfreq_probe,
> + .remove = mtk_cci_devfreq_remove,
> + .driver = {
> + .name = "mediatek-cci-devfreq",
> + .of_match_table = of_match_ptr(mediatek_cci_of_match),
> + },
> +};
> +
> +module_platform_driver(cci_devfreq_driver);
> +
> +MODULE_DESCRIPTION("Mediatek CCI devfreq driver");
> +MODULE_AUTHOR("Andrew-sh.Cheng <andrew-sh.cheng@mediatek.com>");
> +MODULE_LICENSE("GPL v2");