Re: [PATCH v2 2/2] PM / devfreq: mediatek: Introduce MediaTek CCI devfreq driver

Chanwoo Choi
2022-04-13T21:43:53Z

Hi Johnson,

On 22. 4. 8. 14:21, Johnson Wang 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: Johnson Wang <johnson.wang@mediatek.com>
> Signed-off-by: Jia-Wei Chang <jia-wei.chang@mediatek.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 | 479 ++++++++++++++++++++++++++++++
> 3 files changed, 490 insertions(+)
> create mode 100644 drivers/devfreq/mtk-cci-devfreq.c
>
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index 87eb2b837e68..d985597f343f 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
> + 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..53a28e2c88bd
> --- /dev/null
> +++ b/drivers/devfreq/mtk-cci-devfreq.c
> @@ -0,0 +1,479 @@
> +// 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 *cci_dev;
> + struct devfreq *devfreq;
> + struct regulator *proc_reg;
> + struct regulator *sram_reg;
> + struct clk *cci_clk;
> + struct clk *inter_clk;
> + int inter_voltage;
> + int old_voltage;
> + unsigned long old_freq;
> + bool need_voltage_tracking;
> + /* 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;
> +};
> +
> +static int mtk_ccifreq_voltage_tracking(struct mtk_ccifreq_drv *drv,
> + int new_voltage)
> +{

mtk_ccifreq_voltage_tracking() function is only used in
mtk_ccifreq_set_voltage and mtk_ccifreq_set_voltage function doesn't
contain the long codes. I recommend that move
mtk_ccifreq_voltage_tracking code into mtk_ccifreq_set_voltage.

> + const struct mtk_ccifreq_platform_data *soc_data = drv->soc_data;
> + struct device *dev = drv->cci_dev;
> + struct regulator *proc_reg = drv->proc_reg;
> + struct regulator *sram_reg = drv->sram_reg;
> + int old_voltage, old_vsram, new_vsram, vsram, voltage, ret;
> +
> + old_voltage = regulator_get_voltage(proc_reg);
> + if (old_voltage < 0) {
> + dev_err(dev, "invalid vproc value: %d\n", old_voltage);
> + return old_voltage;
> + }
> +
> + old_vsram = regulator_get_voltage(sram_reg);
> + if (old_vsram < 0) {
> + dev_err(dev, "invalid vsram value: %d\n", old_vsram);
> + return old_vsram;
> + }
> +
> + new_vsram = clamp(new_voltage + soc_data->min_volt_shift,
> + soc_data->sram_min_volt, soc_data->sram_max_volt);
> +
> + do {
> + if (old_voltage <= new_voltage) {
> + vsram = clamp(old_voltage + soc_data->max_volt_shift,
> + soc_data->sram_min_volt, new_vsram);
> + ret = regulator_set_voltage(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(proc_reg, voltage,
> + soc_data->proc_max_volt);
> + if (ret) {
> + regulator_set_voltage(sram_reg, old_vsram,
> + soc_data->sram_max_volt);
> + return ret;
> + }
> + } else if (old_voltage > new_voltage) {
> + voltage = max(new_voltage,
> + old_vsram - soc_data->max_volt_shift);
> + ret = regulator_set_voltage(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(sram_reg, vsram,
> + soc_data->sram_max_volt);
> + if (ret) {
> + regulator_set_voltage(proc_reg, old_voltage,
> + soc_data->proc_max_volt);
> + return ret;
> + }
> + }
> +
> + old_voltage = voltage;
> + old_vsram = vsram;
> + } while (voltage != new_voltage || vsram != new_vsram);

It is dangerous if regulator h/w have the issue, it might be never
finished. Need to check the maximum loop or do other way for preventing
the inifinite loop.

> +
> + return 0;
> +}
> +
> +static int mtk_ccifreq_set_voltage(struct mtk_ccifreq_drv *drv, int voltage)
> +{
> + int ret;
> +
> + if (drv->need_voltage_tracking)

You can change this code as following without 'need_voltage_tracking'
variable. It is more simple.

if (drv->sram_reg)

> + ret = mtk_ccifreq_voltage_tracking(drv, voltage);
> + else
> + ret = regulator_set_voltage(drv->proc_reg, voltage,
> + drv->soc_data->proc_max_volt);
> +
> + if (!ret)
> + drv->old_voltage = 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, old_voltage, inter_voltage, target_voltage, ret;
> +
> + if (!drv)
> + return -EINVAL;
> +
> + if (drv->old_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);
> + }
> + voltage = dev_pm_opp_get_voltage(opp);
> + dev_pm_opp_put(opp);
> +
> + old_voltage = drv->old_voltage;
> + if (old_voltage == 0)
> + old_voltage = regulator_get_voltage(drv->proc_reg);
> + if (old_voltage < 0) {
> + dev_err(dev, "invalid vproc value: %d\n", old_voltage);
> + return old_voltage;
> + }

It should be checked on target? I think that you get the voltage on
probe only once and then handle the old_voltage value in
mtk_ccifreq_set_voltage when voltage is changed.

> +
> + mutex_lock(&drv->reg_lock);
> +
> + /* scale up: set voltage first then freq. */
> + target_voltage = max(inter_voltage, voltage);
> + if (old_voltage <= target_voltage) {

you can use drv->old_voltage without 'old_voltage' local variable
if you do as my comment above.

> + 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 < old_voltage) {
> + ret = mtk_ccifreq_set_voltage(drv, voltage);
> + if (ret) {
> + dev_err(dev, "failed to scale down voltage\n");
> + goto out_unlock;
> + }
> + }
> +
> + drv->old_freq = *freq;
> + mutex_unlock(&drv->reg_lock);
> +
> + return 0;
> +
> +out_restore_voltage:
> + mtk_ccifreq_set_voltage(drv, old_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->old_freq) {
> + volt = dev_pm_opp_get_voltage(opp);
> + mtk_ccifreq_set_voltage(drv, volt);

I have a question. Is it no problem? Change the voltage
without any clock change? If voltage is lower than required voltage
level from the specific clock, I think it might be hung.

> + }
> + 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 *cci_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(cci_dev, sizeof(*drv), GFP_KERNEL);
> + if (!drv)
> + return -ENOMEM;
> +
> + drv->cci_dev = cci_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(cci_dev, "cci");
> + if (IS_ERR(drv->cci_clk)) {
> + ret = PTR_ERR(drv->cci_clk);
> + return dev_err_probe(cci_dev, ret,
> + "failed to get cci clk: %d\n", ret);
> + }
> +
> + drv->inter_clk = devm_clk_get(cci_dev, "intermediate");
> + if (IS_ERR(drv->inter_clk)) {
> + ret = PTR_ERR(drv->inter_clk);
> + dev_err_probe(cci_dev, ret,
> + "failed to get intermediate clk: %d\n", ret);
> + goto out_free_resources;
> + }
> +
> + drv->proc_reg = devm_regulator_get_optional(cci_dev, "proc");

nitpick. How about using 'cci' name instead of 'proc'?
Actually, it is difficult to understand the meaning of 'proc' name.

> + if (IS_ERR(drv->proc_reg)) {
> + ret = PTR_ERR(drv->proc_reg);
> + dev_err_probe(cci_dev, ret,
> + "failed to get proc regulator: %d\n", ret);
> + goto out_free_resources;
> + }
> +
> + ret = regulator_enable(drv->proc_reg);
> + if (ret) {
> + dev_err(cci_dev, "failed to enable proc regulator\n");
> + goto out_free_resources;
> + }
> +
> + drv->sram_reg = regulator_get_optional(cci_dev, "sram");
> + if (IS_ERR(drv->sram_reg))
> + drv->sram_reg = NULL;
> + else {
> + ret = regulator_enable(drv->sram_reg);
> + if (ret) {
> + dev_err(cci_dev, "failed to enable sram regulator\n");
> + goto out_free_resources;
> + }
> + }
> +
> + ret = clk_prepare_enable(drv->cci_clk);
> + if (ret)
> + goto out_free_resources;
> +
> + ret = clk_prepare_enable(drv->inter_clk);
> + if (ret)
> + goto out_disable_cci_clk;
> +
> + drv->need_voltage_tracking = (drv->sram_reg != NULL);

As I commented in mtk_ccifreq_set_voltage, you don't need to use
'need_voltage_tracking". Instead just use 'drv->sram_reg direclty.

> +
> + ret = dev_pm_opp_of_add_table(cci_dev);
> + if (ret) {
> + dev_err(cci_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(cci_dev, &rate);
> + if (IS_ERR(opp)) {
> + ret = PTR_ERR(opp);
> + dev_err(cci_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->cci_dev, &rate);
> + if (IS_ERR(opp)) {
> + dev_err(cci_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(cci_dev, "failed to scale to highest voltage %lu in proc_reg\n",
> + opp_volt);
> + goto out_remove_opp_table;
> + }
> +
> + passive_data = devm_kzalloc(cci_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(cci_dev,
> + &mtk_ccifreq_profile,
> + DEVFREQ_GOV_PASSIVE,
> + passive_data);
> + if (IS_ERR(drv->devfreq)) {
> + ret = -EPROBE_DEFER;
> + dev_err(cci_dev, "failed to add devfreq device: %d\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(cci_dev, &drv->opp_nb);
> + if (ret) {
> + dev_err(cci_dev, "failed to register opp notifier: %d\n", ret);
> + goto out_remove_devfreq_device;
> + }
> + return 0;
> +
> +out_remove_devfreq_device:
> + devm_devfreq_remove_device(cci_dev, drv->devfreq);
> +
> +out_remove_opp_table:
> + dev_pm_opp_of_remove_table(cci_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);
> +
> + return ret;
> +}
> +
> +static int mtk_ccifreq_remove(struct platform_device *pdev)
> +{
> + struct device *cci_dev = &pdev->dev;
> + struct mtk_ccifreq_drv *drv;
> +
> + drv = platform_get_drvdata(pdev);
> +
> + dev_pm_opp_unregister_notifier(cci_dev, &drv->opp_nb);
> + dev_pm_opp_of_remove_table(cci_dev);
> + clk_disable_unprepare(drv->inter_clk);
> + clk_disable_unprepare(drv->cci_clk);
> + regulator_disable(drv->proc_reg);
> + if (!IS_ERR(drv->sram_reg))

Better to use the following code.
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,
> +};
> +
> +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,
> +};
> +
> +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 = of_match_ptr(mtk_ccifreq_machines),
> + },
> +};
> +
> +static int __init mtk_ccifreq_platdrv_init(void)
> +{
> + return platform_driver_register(&mtk_ccifreq_platdrv);
> +}
> +module_init(mtk_ccifreq_platdrv_init)
> +
> +static void __exit mtk_ccifreq_platdrv_exit(void)
> +{
> + platform_driver_unregister(&mtk_ccifreq_platdrv);
> +}
> +module_exit(mtk_ccifreq_platdrv_exit)
> +
> +MODULE_DESCRIPTION("MediaTek CCI devfreq driver");
> +MODULE_AUTHOR("Jia-Wei Chang <jia-wei.chang@mediatek.com>");
> +MODULE_LICENSE("GPL v2");

--
Best Regards,
Samsung Electronics
Chanwoo Choi