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References: <20220513032832.17645-1-johnson.wang@mediatek.com> <20220513032832.17645-3-johnson.wang@mediatek.com>
In-Reply-To: <20220513032832.17645-3-johnson.wang@mediatek.com>
From:   Chen-Yu Tsai <wenst@chromium.org>
Date:   Fri, 13 May 2022 11:54:45 +0800
Message-ID: <CAGXv+5Em2eq8g8phC7MVcEP-sCsSsKa9FQjOra2UN3pib_psLA@mail.gmail.com>
Subject: Re: [RESEND v4 2/2] PM / devfreq: mediatek: Introduce MediaTek CCI
 devfreq driver
To:     Johnson Wang <johnson.wang@mediatek.com>
Cc:     cw00.choi@samsung.com, krzk+dt@kernel.org, robh+dt@kernel.org,
        kyungmin.park@samsung.com, djakov@kernel.org, khilman@kernel.org,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, jia-wei.chang@mediatek.com,
        Project_Global_Chrome_Upstream_Group@mediatek.com
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Precedence: bulk

On Fri, May 13, 2022 at 11:31 AM Johnson Wang <johnson.wang@mediatek.com> wrote:
>
> 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@mediatek.com>
> Signed-off-by: Johnson Wang <johnson.wang@mediatek.com>
> Acked-by: Chanwoo Choi <cw00.choi@samsung.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 | 474 ++++++++++++++++++++++++++++++
>  3 files changed, 485 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..aa8c37eb4a06
> --- /dev/null
> +++ b/drivers/devfreq/mtk-cci-devfreq.c
> @@ -0,0 +1,474 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2022 MediaTek Inc.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/devfreq.h>
> +#include <linux/minmax.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_opp.h>
> +#include <linux/regulator/consumer.h>
> +
> +struct mtk_ccifreq_platform_data {
> +       int min_volt_shift;
> +       int max_volt_shift;
> +       int proc_max_volt;
> +       int sram_min_volt;
> +       int sram_max_volt;
> +};
> +
> +struct mtk_ccifreq_drv {
> +       struct device *dev;
> +       struct devfreq *devfreq;
> +       struct regulator *proc_reg;
> +       struct regulator *sram_reg;
> +       struct clk *cci_clk;
> +       struct clk *inter_clk;
> +       int inter_voltage;
> +       int pre_voltage;
> +       unsigned long pre_freq;
> +       /* Avoid race condition for regulators between notify and policy */
> +       struct mutex reg_lock;
> +       struct notifier_block opp_nb;
> +       const struct mtk_ccifreq_platform_data *soc_data;
> +       int vtrack_max;
> +};
> +
> +static int mtk_ccifreq_set_voltage(struct mtk_ccifreq_drv *drv, int new_voltage)
> +{
> +       const struct mtk_ccifreq_platform_data *soc_data = drv->soc_data;
> +       struct device *dev = drv->dev;
> +       int pre_voltage, pre_vsram, new_vsram, vsram, voltage, ret;
> +       int retry_max = drv->vtrack_max;
> +
> +       if (!drv->sram_reg) {
> +               ret = regulator_set_voltage(drv->proc_reg, new_voltage,
> +                                           drv->soc_data->proc_max_volt);
> +               goto out_set_voltage;
> +       }
> +
> +       pre_voltage = regulator_get_voltage(drv->proc_reg);
> +       if (pre_voltage < 0) {
> +               dev_err(dev, "invalid vproc value: %d\n", pre_voltage);
> +               return pre_voltage;
> +       }
> +
> +       pre_vsram = regulator_get_voltage(drv->sram_reg);
> +       if (pre_vsram < 0) {
> +               dev_err(dev, "invalid vsram value: %d\n", pre_vsram);
> +               return pre_vsram;
> +       }
> +
> +       new_vsram = clamp(new_voltage + soc_data->min_volt_shift,
> +                         soc_data->sram_min_volt, soc_data->sram_max_volt);
> +
> +       do {
> +               if (pre_voltage <= new_voltage) {
> +                       vsram = clamp(pre_voltage + soc_data->max_volt_shift,
> +                                     soc_data->sram_min_volt, new_vsram);
> +                       ret = regulator_set_voltage(drv->sram_reg, vsram,
> +                                                   soc_data->sram_max_volt);
> +                       if (ret)
> +                               return ret;
> +
> +                       if (vsram == soc_data->sram_max_volt ||
> +                           new_vsram == soc_data->sram_min_volt)
> +                               voltage = new_voltage;
> +                       else
> +                               voltage = vsram - soc_data->min_volt_shift;
> +
> +                       ret = regulator_set_voltage(drv->proc_reg, voltage,
> +                                                   soc_data->proc_max_volt);
> +                       if (ret) {
> +                               regulator_set_voltage(drv->sram_reg, pre_vsram,
> +                                                     soc_data->sram_max_volt);
> +                               return ret;
> +                       }
> +               } else if (pre_voltage > new_voltage) {
> +                       voltage = max(new_voltage,
> +                                     pre_vsram - soc_data->max_volt_shift);
> +                       ret = regulator_set_voltage(drv->proc_reg, voltage,
> +                                                   soc_data->proc_max_volt);
> +                       if (ret)
> +                               return ret;
> +
> +                       if (voltage == new_voltage)
> +                               vsram = new_vsram;
> +                       else
> +                               vsram = max(new_vsram,
> +                                           voltage + soc_data->min_volt_shift);
> +
> +                       ret = regulator_set_voltage(drv->sram_reg, vsram,
> +                                                   soc_data->sram_max_volt);
> +                       if (ret) {
> +                               regulator_set_voltage(drv->proc_reg, pre_voltage,
> +                                                     soc_data->proc_max_volt);
> +                               return ret;
> +                       }
> +               }
> +
> +               pre_voltage = voltage;
> +               pre_vsram = vsram;
> +
> +               if (--retry_max < 0) {
> +                       dev_err(dev,
> +                               "over loop count, failed to set voltage\n");
> +                       return -EINVAL;
> +               }
> +       } while (voltage != new_voltage || vsram != new_vsram);
> +
> +out_set_voltage:
> +       if (!ret)
> +               drv->pre_voltage = new_voltage;
> +
> +       return ret;
> +}
> +
> +static int mtk_ccifreq_target(struct device *dev, unsigned long *freq,
> +                             u32 flags)
> +{
> +       struct mtk_ccifreq_drv *drv = dev_get_drvdata(dev);
> +       struct clk *cci_pll = clk_get_parent(drv->cci_clk);
> +       struct dev_pm_opp *opp;
> +       unsigned long opp_rate;
> +       int voltage, pre_voltage, inter_voltage, target_voltage, ret;
> +
> +       if (!drv)
> +               return -EINVAL;
> +
> +       if (drv->pre_freq == *freq)
> +               return 0;
> +
> +       inter_voltage = drv->inter_voltage;
> +
> +       opp_rate = *freq;
> +       opp = devfreq_recommended_opp(dev, &opp_rate, 1);
> +       if (IS_ERR(opp)) {
> +               dev_err(dev, "failed to find opp for freq: %ld\n", opp_rate);
> +               return PTR_ERR(opp);
> +       }
> +
> +       mutex_lock(&drv->reg_lock);
> +
> +       voltage = dev_pm_opp_get_voltage(opp);
> +       dev_pm_opp_put(opp);
> +
> +       if (unlikely(drv->pre_voltage <= 0))
> +               pre_voltage = regulator_get_voltage(drv->proc_reg);
> +       else
> +               pre_voltage = drv->pre_voltage;

Could you explain why the previous voltage setting is cached like this?

The CCI is sharing the regulator supply with one of the CPU clusters,
and cpufreq could also change the voltage, so it's better to always
retrieve the current setting directly from the regulator core. And
those values might be cached iun the core, so it's unlikely to incur
a significant cost.

> +
> +       if (pre_voltage < 0) {
> +               dev_err(dev, "invalid vproc value: %d\n", pre_voltage);
> +               return pre_voltage;
> +       }
> +
> +       /* scale up: set voltage first then freq. */
> +       target_voltage = max(inter_voltage, voltage);
> +       if (pre_voltage <= target_voltage) {
> +               ret = mtk_ccifreq_set_voltage(drv, target_voltage);
> +               if (ret) {
> +                       dev_err(dev, "failed to scale up voltage\n");
> +                       goto out_restore_voltage;
> +               }
> +       }
> +
> +       /* switch the cci clock to intermediate clock source. */
> +       ret = clk_set_parent(drv->cci_clk, drv->inter_clk);
> +       if (ret) {
> +               dev_err(dev, "failed to re-parent cci clock\n");
> +               goto out_restore_voltage;
> +       }
> +
> +       /* set the original clock to target rate. */
> +       ret = clk_set_rate(cci_pll, *freq);
> +       if (ret) {
> +               dev_err(dev, "failed to set cci pll rate: %d\n", ret);
> +               clk_set_parent(drv->cci_clk, cci_pll);
> +               goto out_restore_voltage;
> +       }
> +
> +       /* switch the cci clock back to the original clock source. */
> +       ret = clk_set_parent(drv->cci_clk, cci_pll);
> +       if (ret) {
> +               dev_err(dev, "failed to re-parent cci clock\n");
> +               mtk_ccifreq_set_voltage(drv, inter_voltage);
> +               goto out_unlock;
> +       }
> +
> +       /*
> +        * If the new voltage is lower than the intermediate voltage or the
> +        * original voltage, scale down to the new voltage.
> +        */
> +       if (voltage < inter_voltage || voltage < pre_voltage) {
> +               ret = mtk_ccifreq_set_voltage(drv, voltage);
> +               if (ret) {
> +                       dev_err(dev, "failed to scale down voltage\n");
> +                       goto out_unlock;
> +               }
> +       }
> +
> +       drv->pre_freq = *freq;
> +       mutex_unlock(&drv->reg_lock);
> +
> +       return 0;
> +
> +out_restore_voltage:
> +       mtk_ccifreq_set_voltage(drv, pre_voltage);
> +
> +out_unlock:
> +       mutex_unlock(&drv->reg_lock);
> +       return ret;
> +}
> +
> +static int mtk_ccifreq_opp_notifier(struct notifier_block *nb,
> +                                   unsigned long event, void *data)
> +{
> +       struct dev_pm_opp *opp = data;
> +       struct mtk_ccifreq_drv *drv;
> +       unsigned long freq, volt;
> +
> +       drv = container_of(nb, struct mtk_ccifreq_drv, opp_nb);
> +
> +       if (event == OPP_EVENT_ADJUST_VOLTAGE) {
> +               freq = dev_pm_opp_get_freq(opp);
> +
> +               mutex_lock(&drv->reg_lock);
> +               /* current opp item is changed */
> +               if (freq == drv->pre_freq) {
> +                       volt = dev_pm_opp_get_voltage(opp);
> +                       mtk_ccifreq_set_voltage(drv, volt);
> +               }
> +               mutex_unlock(&drv->reg_lock);
> +       }
> +
> +       return 0;
> +}
> +
> +static struct devfreq_dev_profile mtk_ccifreq_profile = {
> +       .target = mtk_ccifreq_target,
> +};
> +
> +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);
> +               dev_err_probe(dev, ret,
> +                             "failed to get intermediate clk: %d\n", ret);
> +               goto out_free_resources;
> +       }
> +
> +       drv->proc_reg = devm_regulator_get_optional(dev, "proc");
> +       if (IS_ERR(drv->proc_reg)) {
> +               ret = PTR_ERR(drv->proc_reg);
> +               dev_err_probe(dev, ret,
> +                             "failed to get proc regulator: %d\n", ret);
> +               goto out_free_resources;
> +       }
> +
> +       ret = regulator_enable(drv->proc_reg);
> +       if (ret) {
> +               dev_err(dev, "failed to enable proc regulator\n");
> +               goto out_free_resources;
> +       }
> +
> +       drv->sram_reg = regulator_get_optional(dev, "sram");

devm_ for this as well?

> +       if (IS_ERR(drv->sram_reg))
> +               drv->sram_reg = NULL;
> +       else {
> +               ret = regulator_enable(drv->sram_reg);
> +               if (ret) {
> +                       dev_err(dev, "failed to enable sram regulator\n");
> +                       goto out_free_resources;
> +               }
> +       }
> +
> +       /*
> +        * We assume min voltage is 0 and tracking target voltage using
> +        * min_volt_shift for each iteration.
> +        * The retry_max is 3 times of expeted iteration count.

expected?

> +        */
> +       drv->vtrack_max = 3 * DIV_ROUND_UP(max(drv->soc_data->sram_max_volt,
> +                                              drv->soc_data->proc_max_volt),
> +                                          drv->soc_data->min_volt_shift);
> +
> +       ret = clk_prepare_enable(drv->cci_clk);
> +       if (ret)
> +               goto out_free_resources;
> +
> +       ret = clk_prepare_enable(drv->inter_clk);

You don't need to enable the intermediate clock here. You shouldn't need
to at all, as the CCF core will do it when the CCI clock is reparented
over to it.

> +       if (ret)
> +               goto out_disable_cci_clk;
> +
> +       ret = dev_pm_opp_of_add_table(dev);
> +       if (ret) {
> +               dev_err(dev, "failed to add opp table: %d\n", ret);
> +               goto out_disable_inter_clk;
> +       }
> +
> +       rate = clk_get_rate(drv->inter_clk);
> +       opp = dev_pm_opp_find_freq_ceil(dev, &rate);
> +       if (IS_ERR(opp)) {
> +               ret = PTR_ERR(opp);
> +               dev_err(dev, "failed to get intermediate opp: %d\n", ret);
> +               goto out_remove_opp_table;
> +       }
> +       drv->inter_voltage = dev_pm_opp_get_voltage(opp);
> +       dev_pm_opp_put(opp);
> +
> +       rate = U32_MAX;
> +       opp = dev_pm_opp_find_freq_floor(drv->dev, &rate);
> +       if (IS_ERR(opp)) {
> +               dev_err(dev, "failed to get opp\n");
> +               ret = PTR_ERR(opp);
> +               goto out_remove_opp_table;
> +       }
> +
> +       opp_volt = dev_pm_opp_get_voltage(opp);
> +       dev_pm_opp_put(opp);
> +       ret = mtk_ccifreq_set_voltage(drv, opp_volt);
> +       if (ret) {
> +               dev_err(dev, "failed to scale to highest voltage %lu in proc_reg\n",
> +                       opp_volt);
> +               goto out_remove_opp_table;
> +       }
> +
> +       passive_data = devm_kzalloc(dev, sizeof(struct devfreq_passive_data),
> +                                   GFP_KERNEL);
> +       if (!passive_data) {
> +               ret = -ENOMEM;
> +               goto out_remove_opp_table;
> +       }
> +
> +       passive_data->parent_type = CPUFREQ_PARENT_DEV;
> +       drv->devfreq = devm_devfreq_add_device(dev, &mtk_ccifreq_profile,
> +                                              DEVFREQ_GOV_PASSIVE,
> +                                              passive_data);
> +       if (IS_ERR(drv->devfreq)) {
> +               ret = -EPROBE_DEFER;
> +               dev_err(dev, "failed to add devfreq device: %ld\n",
> +                       PTR_ERR(drv->devfreq));
> +               goto out_remove_opp_table;
> +       }
> +
> +       drv->opp_nb.notifier_call = mtk_ccifreq_opp_notifier;
> +       ret = dev_pm_opp_register_notifier(dev, &drv->opp_nb);
> +       if (ret) {
> +               dev_err(dev, "failed to register opp notifier: %d\n", ret);
> +               goto out_remove_devfreq_device;
> +       }
> +       return 0;
> +
> +out_remove_devfreq_device:
> +       devm_devfreq_remove_device(dev, drv->devfreq);
> +
> +out_remove_opp_table:
> +       dev_pm_opp_of_remove_table(dev);
> +
> +out_disable_inter_clk:
> +       clk_disable_unprepare(drv->inter_clk);
> +
> +out_disable_cci_clk:
> +       clk_disable_unprepare(drv->cci_clk);
> +
> +out_free_resources:
> +       if (regulator_is_enabled(drv->proc_reg))
> +               regulator_disable(drv->proc_reg);
> +       if (drv->sram_reg && regulator_is_enabled(drv->sram_reg))
> +               regulator_disable(drv->sram_reg);
> +
> +       if (!IS_ERR(drv->proc_reg))
> +               regulator_put(drv->proc_reg);
> +       if (!IS_ERR(drv->sram_reg))
> +               regulator_put(drv->sram_reg);
> +       if (!IS_ERR(drv->cci_clk))
> +               clk_put(drv->cci_clk);
> +       if (!IS_ERR(drv->inter_clk))
> +               clk_put(drv->inter_clk);

You don't need to "put" the resources you got using devm_ variants.
If you really want to, you need to use devm_(clk|regulator)_put.

> +
> +       return ret;
> +}
> +
> +static int mtk_ccifreq_remove(struct platform_device *pdev)
> +{
> +       struct device *dev = &pdev->dev;
> +       struct mtk_ccifreq_drv *drv;
> +
> +       drv = platform_get_drvdata(pdev);
> +
> +       dev_pm_opp_unregister_notifier(dev, &drv->opp_nb);
> +       dev_pm_opp_of_remove_table(dev);
> +       clk_disable_unprepare(drv->inter_clk);
> +       clk_disable_unprepare(drv->cci_clk);
> +       regulator_disable(drv->proc_reg);
> +       if (drv->sram_reg)
> +               regulator_disable(drv->sram_reg);
> +
> +       return 0;
> +}
> +
> +static const struct mtk_ccifreq_platform_data mt8183_platform_data = {
> +       .min_volt_shift = 100000,
> +       .max_volt_shift = 200000,
> +       .proc_max_volt = 1150000,
> +       .sram_min_volt = 0,
> +       .sram_max_volt = 1150000,

AFAICT there's no sram supply for MT8183, so set max to zero as well?
And you can just drop the two lines instead of explicitly setting
them to zero.

> +};
> +
> +static const struct mtk_ccifreq_platform_data mt8186_platform_data = {
> +       .min_volt_shift = 100000,
> +       .max_volt_shift = 250000,
> +       .proc_max_volt = 1118750,
> +       .sram_min_volt = 850000,
> +       .sram_max_volt = 1118750,

A side note about this: the min/max voltage values should also be set
on the regulator nodes in the device tree. The range then gets enforced
by the regulator core.


Regards
ChenYu

> +};
> +
> +static const struct of_device_id mtk_ccifreq_machines[] = {
> +       { .compatible = "mediatek,mt8183-cci", .data = &mt8183_platform_data },
> +       { .compatible = "mediatek,mt8186-cci", .data = &mt8186_platform_data },
> +       { },
> +};
> +MODULE_DEVICE_TABLE(of, mtk_ccifreq_machines);
> +
> +static struct platform_driver mtk_ccifreq_platdrv = {
> +       .probe  = mtk_ccifreq_probe,
> +       .remove = mtk_ccifreq_remove,
> +       .driver = {
> +               .name = "mtk-ccifreq",
> +               .of_match_table = mtk_ccifreq_machines,
> +       },
> +};
> +module_platform_driver(mtk_ccifreq_platdrv);
> +
> +MODULE_DESCRIPTION("MediaTek CCI devfreq driver");
> +MODULE_AUTHOR("Jia-Wei Chang <jia-wei.chang@mediatek.com>");
> +MODULE_LICENSE("GPL v2");
> --
> 2.18.0
>
>
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