Re: [PATCH v5 7/8] PM / devfreq: rockchip: add devfreq driver for rk3399 dmc

[Chanwoo Choi <cw00.choi@samsung.com>]

Hi Lin,

I add the some comment on below.

If you modify them, feel free to add the my reviewed tag on next version:
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>

On 2016년 08월 10일 12:26, Lin Huang wrote:
> base on dfi result, we do ddr frequency scaling, register
> dmc driver to devfreq framework, and use simple-ondemand
> policy.
> 
> Signed-off-by: Lin Huang <hl@rock-chips.com>
> ---
> Changes in v5:
> - improve dmc driver suggest by Chanwoo Choi
> 
> Changes in v4:
> - use arm_smccc_smc() function talk to bl31
> - delete rockchip_dmc.c file and config
> - delete dmc_notify
> - adjust probe order
> 
> Changes in v3:
> - operate dram setting through sip call
> - imporve set rate flow
> 
> Changes in v2:
> - None
> 
> Changes in v1:
> - move dfi controller to event
> - fix set voltage sequence when set rate fail
> - change Kconfig type from tristate to bool
> - move unuse EXPORT_SYMBOL_GPL()
> 
>  drivers/devfreq/Kconfig      |   9 +
>  drivers/devfreq/Makefile     |   1 +
>  drivers/devfreq/rk3399_dmc.c | 512 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 522 insertions(+)
>  create mode 100644 drivers/devfreq/rk3399_dmc.c
> 
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index a5be56e..749499d 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -100,6 +100,15 @@ config ARM_TEGRA_DEVFREQ
>           It reads ACTMON counters of memory controllers and adjusts the
>           operating frequencies and voltages with OPP support.
>  
> +config ARM_RK3399_DMC_DEVFREQ
> +	tristate "ARM RK3399 DMC DEVFREQ Driver"

depend on ARCH_ROCKCHIP ?

> +	select PM_OPP
> +	select DEVFREQ_GOV_SIMPLE_ONDEMAND

This entry needs the following command in Kconfig:
	select DEVFREQ_EVENT_ROCKCHIP_DFI

> +	help
> +          This adds the DEVFREQ driver for the RK3399 dmc(Dynamic Memory Controller).

Use a capital letter for and abbreviation.

s/dmc -> DMC

> +          It sets the frequency for the memory controller and reads the usage counts
> +          from hardware.
> +
>  source "drivers/devfreq/event/Kconfig"
>  
>  endif # PM_DEVFREQ
> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
> index 09f11d9..70d9549 100644
> --- a/drivers/devfreq/Makefile
> +++ b/drivers/devfreq/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
>  # DEVFREQ Drivers
>  obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
>  obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra-devfreq.o
> +obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o

The  entry would be positioned
The position of CONFIG_ARM_RK3399_DMC_DEVFREQ would be good on
between EXYNOS_BUS_DEVFREQ and TEGRA_DEVFREQ because of the alphabetical order.

>  
>  # DEVFREQ Event Drivers
>  obj-$(CONFIG_PM_DEVFREQ_EVENT)		+= event/
> diff --git a/drivers/devfreq/rk3399_dmc.c b/drivers/devfreq/rk3399_dmc.c
> new file mode 100644
> index 0000000..c1157ba
> --- /dev/null
> +++ b/drivers/devfreq/rk3399_dmc.c
> @@ -0,0 +1,512 @@
> +/*
> + * Copyright (c) 2016, Fuzhou Rockchip Electronics Co., Ltd.
> + * Author: Lin Huang <hl@rock-chips.com>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + */
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/devfreq.h>
> +#include <linux/devfreq-event.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_opp.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/rwsem.h>
> +#include <linux/suspend.h>
> +
> +#include <soc/rockchip/rockchip_sip.h>
> +
> +struct dram_timing {
> +	unsigned int ddr3_speed_bin;
> +	unsigned int pd_idle;
> +	unsigned int sr_idle;
> +	unsigned int sr_mc_gate_idle;
> +	unsigned int srpd_lite_idle;
> +	unsigned int standby_idle;
> +	unsigned int dram_dll_dis_freq;
> +	unsigned int phy_dll_dis_freq;
> +	unsigned int ddr3_odt_dis_freq;
> +	unsigned int ddr3_drv;
> +	unsigned int ddr3_odt;
> +	unsigned int phy_ddr3_ca_drv;
> +	unsigned int phy_ddr3_dq_drv;
> +	unsigned int phy_ddr3_odt;
> +	unsigned int lpddr3_odt_dis_freq;
> +	unsigned int lpddr3_drv;
> +	unsigned int lpddr3_odt;
> +	unsigned int phy_lpddr3_ca_drv;
> +	unsigned int phy_lpddr3_dq_drv;
> +	unsigned int phy_lpddr3_odt;
> +	unsigned int lpddr4_odt_dis_freq;
> +	unsigned int lpddr4_drv;
> +	unsigned int lpddr4_dq_odt;
> +	unsigned int lpddr4_ca_odt;
> +	unsigned int phy_lpddr4_ca_drv;
> +	unsigned int phy_lpddr4_ck_cs_drv;
> +	unsigned int phy_lpddr4_dq_drv;
> +	unsigned int phy_lpddr4_odt;
> +};
> +
> +struct rk3399_dmcfreq {
> +	struct device *dev;
> +	struct devfreq *devfreq;
> +	struct devfreq_simple_ondemand_data ondemand_data;
> +	struct clk *dmc_clk;
> +	struct devfreq_event_dev *edev;
> +	struct mutex lock;
> +	struct dram_timing *timing;
> +
> +	/*
> +	 * DDR Converser of Frequency (DCF) is used to implement DDR frequency
> +	 * conversion without the participation of CPU, we will implement and
> +	 * control it in arm trust firmware.
> +	 */
> +	wait_queue_head_t	wait_dcf_queue;
> +	int irq;
> +	int wait_dcf_flag;
> +	struct regulator *vdd_center;
> +	unsigned long rate, target_rate;
> +	unsigned long volt, target_volt;
> +	struct dev_pm_opp *curr_opp;
> +};
> +
> +static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq,
> +				 u32 flags)
> +{
> +	struct rk3399_dmcfreq *dmcfreq = dev_get_drvdata(dev);
> +	struct dev_pm_opp *opp;
> +	unsigned long old_clk_rate = dmcfreq->rate;
> +	unsigned long target_volt, target_rate;
> +	int err;
> +
> +	rcu_read_lock();
> +	opp = devfreq_recommended_opp(dev, freq, flags);
> +	if (IS_ERR(opp)) {
> +		rcu_read_unlock();
> +		return PTR_ERR(opp);
> +	}
> +
> +	target_rate = dev_pm_opp_get_freq(opp);
> +	target_volt = dev_pm_opp_get_voltage(opp);
> +
> +	dmcfreq->rate = dev_pm_opp_get_freq(dmcfreq->curr_opp);
> +	dmcfreq->volt = dev_pm_opp_get_voltage(dmcfreq->curr_opp);
> +
> +	rcu_read_unlock();
> +
> +	if (dmcfreq->rate == target_rate)
> +		return 0;
> +
> +	mutex_lock(&dmcfreq->lock);
> +
> +	/*
> +	 * If frequency scaling from low to high, adjust voltage first.
> +	 * If frequency scaling from high to low, adjust frequency first.
> +	 */
> +	if (old_clk_rate < target_rate) {
> +		err = regulator_set_voltage(dmcfreq->vdd_center, target_volt,
> +					    target_volt);
> +		if (err) {
> +			dev_err(dev, "Cannot to set voltage %lu uV\n",
> +				target_volt);
> +			goto out;
> +		}
> +	}
> +	dmcfreq->wait_dcf_flag = 1;
> +
> +	err = clk_set_rate(dmcfreq->dmc_clk, target_rate);
> +	if (err) {
> +		dev_err(dev, "Cannot to set frequency %lu (%d)\n",
> +			target_rate, err);
> +		regulator_set_voltage(dmcfreq->vdd_center, dmcfreq->volt,
> +				      dmcfreq->volt);
> +		goto out;
> +	}
> +
> +	/*
> +	 * Wait until bcf irq happen, it means freq scaling finish in
> +	 * arm trust firmware, use 100ms as timeout time.
> +	 */
> +	if (!wait_event_timeout(dmcfreq->wait_dcf_queue,
> +				!dmcfreq->wait_dcf_flag, HZ / 10))
> +		dev_warn(dev, "Timeout waiting for dcf interrupt\n");
> +
> +	/*
> +	 * Check the dpll rate,
> +	 * There only two result we will get,
> +	 * 1. Ddr frequency scaling fail, we still get the old rate.
> +	 * 2. Ddr frequency scaling sucessful, we get the rate we set.
> +	 */
> +	dmcfreq->rate = clk_get_rate(dmcfreq->dmc_clk);
> +
> +	/* If get the incorrect rate, set voltage to old value. */
> +	if (dmcfreq->rate != target_rate) {
> +		dev_err(dev, "Get wrong ddr frequency, Request frequency %lu,\
> +			Current frequency %lu\n", target_rate, dmcfreq->rate);
> +		regulator_set_voltage(dmcfreq->vdd_center, dmcfreq->volt,
> +				      dmcfreq->volt);
> +		goto out;
> +	} else if (old_clk_rate > target_rate)
> +		err = regulator_set_voltage(dmcfreq->vdd_center, target_volt,
> +					    target_volt);
> +	if (err)
> +		dev_err(dev, "Cannot to set vol %lu uV\n", target_volt);
> +
> +	dmcfreq->curr_opp = opp;
> +out:
> +	mutex_unlock(&dmcfreq->lock);
> +	return err;
> +}
> +
> +static int rk3399_dmcfreq_get_dev_status(struct device *dev,
> +					 struct devfreq_dev_status *stat)
> +{
> +	struct rk3399_dmcfreq *dmcfreq = dev_get_drvdata(dev);
> +	struct devfreq_event_data edata;
> +	int ret = 0;
> +
> +	ret = devfreq_event_get_event(dmcfreq->edev, &edata);
> +	if (ret < 0)
> +		return ret;
> +
> +	stat->current_frequency = dmcfreq->rate;
> +	stat->busy_time = edata.load_count;
> +	stat->total_time = edata.total_count;
> +
> +	return ret;
> +}
> +
> +static int rk3399_dmcfreq_get_cur_freq(struct device *dev, unsigned long *freq)
> +{
> +	struct rk3399_dmcfreq *dmcfreq = dev_get_drvdata(dev);
> +
> +	*freq = dmcfreq->rate;
> +
> +	return 0;
> +}
> +
> +static void rk3399_dmcfreq_exit(struct device *dev)
> +{
> +	struct platform_device *pdev = container_of(dev,
> +						    struct platform_device,
> +						    dev);
> +	struct rk3399_dmcfreq *dmcfreq = platform_get_drvdata(pdev);
> +
> +	devfreq_unregister_opp_notifier(dev, dmcfreq->devfreq);

As I mentioned on previous patches on v4,
You'd better to use the devm_devfreq_register_opp_notifier().
If you use devm_devfreq_register_opp_notifier(), you don't need
to handle the unregistration operation.


> +}
> +
> +static struct devfreq_dev_profile rk3399_devfreq_dmc_profile = {
> +	.polling_ms	= 200,
> +	.target		= rk3399_dmcfreq_target,
> +	.get_dev_status	= rk3399_dmcfreq_get_dev_status,
> +	.get_cur_freq	= rk3399_dmcfreq_get_cur_freq,
> +	.exit		= rk3399_dmcfreq_exit,
> +};
> +
> +static __maybe_unused int rk3399_dmcfreq_suspend(struct device *dev)
> +{
> +	struct rk3399_dmcfreq *dmcfreq = dev_get_drvdata(dev);
> +	int ret = 0;
> +
> +	ret = devfreq_event_disable_edev(dmcfreq->edev);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to disable the devfreq-event devices\n");
> +		return ret;
> +	}
> +
> +	ret = devfreq_suspend_device(dmcfreq->devfreq);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to suspend the devfreq devices\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static __maybe_unused int rk3399_dmcfreq_resume(struct device *dev)
> +{
> +	struct rk3399_dmcfreq *dmcfreq = dev_get_drvdata(dev);
> +	int ret = 0;
> +
> +	ret = devfreq_event_enable_edev(dmcfreq->edev);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to enable the devfreq-event devices\n");
> +		return ret;
> +	}
> +
> +	ret = devfreq_resume_device(dmcfreq->devfreq);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to resume the devfreq devices\n");
> +		return ret;
> +	}
> +	return ret;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(rk3399_dmcfreq_pm, rk3399_dmcfreq_suspend,
> +			 rk3399_dmcfreq_resume);
> +
> +static irqreturn_t rk3399_dmc_irq(int irq, void *dev_id)
> +{
> +	struct rk3399_dmcfreq *dmcfreq = dev_id;
> +	struct arm_smccc_res res;
> +
> +	dmcfreq->wait_dcf_flag = 0;
> +	wake_up(&dmcfreq->wait_dcf_queue);
> +
> +	/* Clear the DCF interrupt */
> +	arm_smccc_smc(SIP_DDR_FREQ, 0, 0, CONFIG_DRAM_CLR_IRQ,
> +		      0, 0, 0, 0, &res);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static struct dram_timing *of_get_ddr_timings(struct device *dev,
> +					      struct device_node *np)
> +{
> +	struct dram_timing	*timing = NULL;
> +	struct device_node	*np_tim;
> +	int ret;
> +
> +	np_tim = of_parse_phandle(np, "ddr_timing", 0);
> +	if (np_tim) {
> +		timing = devm_kzalloc(dev, sizeof(*timing), GFP_KERNEL);
> +		if (!timing)
> +			goto err;
> +
> +		ret = of_property_read_u32(np_tim, "ddr3_speed_bin",
> +					   &timing->ddr3_speed_bin);
> +		ret |= of_property_read_u32(np_tim, "pd_idle",
> +					    &timing->pd_idle);
> +		ret |= of_property_read_u32(np_tim, "sr_idle",
> +					    &timing->sr_idle);
> +		ret |= of_property_read_u32(np_tim, "sr_mc_gate_idle",
> +					    &timing->sr_mc_gate_idle);
> +		ret |= of_property_read_u32(np_tim, "srpd_lite_idle",
> +					    &timing->srpd_lite_idle);
> +		ret |= of_property_read_u32(np_tim, "standby_idle",
> +					    &timing->standby_idle);
> +		ret |= of_property_read_u32(np_tim, "dram_dll_dis_freq",
> +					    &timing->dram_dll_dis_freq);
> +		ret |= of_property_read_u32(np_tim, "phy_dll_dis_freq",
> +					    &timing->phy_dll_dis_freq);
> +		ret |= of_property_read_u32(np_tim, "ddr3_odt_dis_freq",
> +					    &timing->ddr3_odt_dis_freq);
> +		ret |= of_property_read_u32(np_tim, "ddr3_drv",
> +					    &timing->ddr3_drv);
> +		ret |= of_property_read_u32(np_tim, "ddr3_odt",
> +					    &timing->ddr3_odt);
> +		ret |= of_property_read_u32(np_tim, "phy_ddr3_ca_drv",
> +					    &timing->phy_ddr3_ca_drv);
> +		ret |= of_property_read_u32(np_tim, "phy_ddr3_dq_drv",
> +					    &timing->phy_ddr3_dq_drv);
> +		ret |= of_property_read_u32(np_tim, "phy_ddr3_odt",
> +					    &timing->phy_ddr3_odt);
> +		ret |= of_property_read_u32(np_tim, "lpddr3_odt_dis_freq",
> +					    &timing->lpddr3_odt_dis_freq);
> +		ret |= of_property_read_u32(np_tim, "lpddr3_drv",
> +					    &timing->lpddr3_drv);
> +		ret |= of_property_read_u32(np_tim, "lpddr3_odt",
> +					    &timing->lpddr3_odt);
> +		ret |= of_property_read_u32(np_tim, "phy_lpddr3_ca_drv",
> +					    &timing->phy_lpddr3_ca_drv);
> +		ret |= of_property_read_u32(np_tim, "phy_lpddr3_dq_drv",
> +					    &timing->phy_lpddr3_dq_drv);
> +		ret |= of_property_read_u32(np_tim, "phy_lpddr3_odt",
> +					    &timing->phy_lpddr3_odt);
> +		ret |= of_property_read_u32(np_tim, "lpddr4_odt_dis_freq",
> +					    &timing->lpddr4_odt_dis_freq);
> +		ret |= of_property_read_u32(np_tim, "lpddr4_drv",
> +					    &timing->lpddr4_drv);
> +		ret |= of_property_read_u32(np_tim, "lpddr4_dq_odt",
> +					    &timing->lpddr4_dq_odt);
> +		ret |= of_property_read_u32(np_tim, "lpddr4_ca_odt",
> +					    &timing->lpddr4_ca_odt);
> +		ret |= of_property_read_u32(np_tim, "phy_lpddr4_ca_drv",
> +					    &timing->phy_lpddr4_ca_drv);
> +		ret |= of_property_read_u32(np_tim, "phy_lpddr4_ck_cs_drv",
> +					    &timing->phy_lpddr4_ck_cs_drv);
> +		ret |= of_property_read_u32(np_tim, "phy_lpddr4_dq_drv",
> +					    &timing->phy_lpddr4_dq_drv);
> +		ret |= of_property_read_u32(np_tim, "phy_lpddr4_odt",
> +					    &timing->phy_lpddr4_odt);
> +		if (ret) {
> +			devm_kfree(dev, timing);
> +			goto err;
> +		}
> +		of_node_put(np_tim);
> +		return timing;
> +	}
> +
> +err:
> +	if (timing) {
> +		devm_kfree(dev, timing);
> +		timing = NULL;
> +	}
> +	of_node_put(np_tim);
> +	return timing;
> +}
> +
> +static int rk3399_dmcfreq_probe(struct platform_device *pdev)
> +{
> +	struct arm_smccc_res res;
> +	struct device *dev = &pdev->dev;
> +	struct device_node *np = pdev->dev.of_node;
> +	uint64_t param = 0;
> +	struct rk3399_dmcfreq *data;
> +	int ret, irq, index, size;
> +	uint32_t *timing;
> +	struct dev_pm_opp *opp;
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0) {
> +		dev_err(&pdev->dev, "Cannot get the dmc interrupt resource\n");
> +		return -EINVAL;
> +	}
> +	data = devm_kzalloc(dev, sizeof(struct rk3399_dmcfreq), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	mutex_init(&data->lock);
> +
> +	data->vdd_center = devm_regulator_get(dev, "center");
> +	if (IS_ERR(data->vdd_center)) {
> +		dev_err(dev, "Cannot get the regulator \"center\"\n");
> +		return PTR_ERR(data->vdd_center);
> +	}
> +
> +	data->dmc_clk = devm_clk_get(dev, "dmc_clk");
> +	if (IS_ERR(data->dmc_clk)) {
> +		dev_err(dev, "Cannot get the clk dmc_clk\n");
> +		return PTR_ERR(data->dmc_clk);
> +	};
> +
> +	data->irq = irq;
> +	ret = devm_request_irq(dev, irq, rk3399_dmc_irq, 0,
> +			       dev_name(dev), data);
> +	if (ret) {
> +		dev_err(dev, "Failed to request dmc irq: %d\n", ret);
> +		return ret;
> +	}
> +
> +	/*
> +	 * Get dram timing and pass it to arm trust firmware,
> +	 * the dram drvier in arm trust firmware will get these
> +	 * timing and to do dram initial.
> +	 */
> +	data->timing = of_get_ddr_timings(dev, np);
> +	if (data->timing) {
> +		timing = (uint32_t *)data->timing;
> +		size = sizeof(struct dram_timing) / 4;
> +		for (index = 0; index < size; index++) {
> +			param = index;
> +			param = param << 32 | *timing++;
> +			arm_smccc_smc(SIP_DDR_FREQ, param, 0,
> +				      CONFIG_DRAM_SET_PARAM, 0, 0, 0, 0, &res);
> +			if (res.a0) {
> +				dev_err(dev, "Failed to set dram param: %ld\n",
> +					res.a0);
> +				return -EINVAL;
> +			}
> +			param = 0;
> +		}
> +	}
> +
> +	arm_smccc_smc(SIP_DDR_FREQ, 0, 0, CONFIG_DRAM_INIT,
> +		      0, 0, 0, 0, &res);
> +
> +	init_waitqueue_head(&data->wait_dcf_queue);
> +	data->wait_dcf_flag = 0;
> +
> +	data->edev = devfreq_event_get_edev_by_phandle(dev, 0);
> +	if (IS_ERR(data->edev))
> +		return -EPROBE_DEFER;
> +
> +	ret = devfreq_event_enable_edev(data->edev);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to enable devfreq-event devices\n");
> +		return ret;
> +	}
> +
> +	/*
> +	 * We add a devfreq driver to our parent since it has a device tree node
> +	 * with operating points.
> +	 */
> +	if (dev_pm_opp_of_add_table(dev)) {
> +		dev_err(dev, "Invalid operating-points in device tree.\n");
> +		rcu_read_unlock();
> +		return -EINVAL;
> +	}
> +
> +	of_property_read_u32(np, "upthreshold",
> +			     &data->ondemand_data.upthreshold);
> +	of_property_read_u32(np, "downdifferential",
> +			     &data->ondemand_data.downdifferential);
> +
> +	data->rate = clk_get_rate(data->dmc_clk);
> +
> +	rcu_read_lock();
> +	opp = devfreq_recommended_opp(dev, &data->rate, 0);
> +	if (IS_ERR(opp)) {
> +		rcu_read_unlock();
> +		return PTR_ERR(opp);
> +	}
> +	rcu_read_unlock();
> +	data->curr_opp = opp;
> +
> +	rk3399_devfreq_dmc_profile.initial_freq = data->rate;
> +
> +	data->devfreq = devfreq_add_device(dev,
> +					   &rk3399_devfreq_dmc_profile,
> +					   "simple_ondemand",
> +					   &data->ondemand_data);
> +	if (IS_ERR(data->devfreq))
> +		return PTR_ERR(data->devfreq);
> +	devfreq_register_opp_notifier(dev, data->devfreq);

ditto. devm_devfreq_register_opp_notifier()

> +
> +	data->dev = dev;
> +	platform_set_drvdata(pdev, data);
> +
> +	return 0;
> +}
> +
> +static int rk3399_dmcfreq_remove(struct platform_device *pdev)
> +{
> +	struct rk3399_dmcfreq *dmcfreq = platform_get_drvdata(pdev);
> +
> +	devfreq_remove_device(dmcfreq->devfreq);

I think that you don't need to call this function. 

> +	regulator_put(dmcfreq->vdd_center);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id rk3399dmc_devfreq_of_match[] = {
> +	{ .compatible = "rockchip,rk3399-dmc" },
> +	{ },
> +};
> +
> +static struct platform_driver rk3399_dmcfreq_driver = {
> +	.probe	= rk3399_dmcfreq_probe,
> +	.remove	= rk3399_dmcfreq_remove,
> +	.driver = {
> +		.name	= "rk3399-dmc-freq",
> +		.pm	= &rk3399_dmcfreq_pm,
> +		.of_match_table = rk3399dmc_devfreq_of_match,
> +	},
> +};
> +module_platform_driver(rk3399_dmcfreq_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Lin Huang <hl@rock-chips.com>");
> +MODULE_DESCRIPTION("RK3399 dmcfreq driver with devfreq framework");
> 

Regards,
Chanwoo Choi