Date:	Tue, 2 Aug 2016 09:03:32 +0800
From:	hl <hl@...k-chips.com>
To:	Chanwoo Choi <cw00.choi@...sung.com>, heiko@...ech.de
Cc:	tixy@...aro.org, dbasehore@...omium.org, airlied@...ux.ie,
	mturquette@...libre.com, typ@...k-chips.com, sboyd@...eaurora.org,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	dianders@...omium.org, linux-rockchip@...ts.infradead.org,
	kyungmin.park@...sung.com, myungjoo.ham@...sung.com,
	linux-arm-kernel@...ts.infradead.org, mark.yao@...k-chips.com
Subject: Re: [PATCH v4 6/7] PM / devfreq: rockchip: add devfreq driver for
 rk3399 dmc

Hi Chanwoo Choi,

     Thanks for reviewing so carefully. And i have some question:

On 2016年08月01日 18:28, Chanwoo Choi wrote:
> Hi Lin,
>
> As I mentioned on patch5, you better to make the documentation as following:
> - Documentation/devicetree/bindings/devfreq/rk3399_dmc.txt
> And, I add the comments.
>
>
> On 2016년 07월 29일 16:57, 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@...k-chips.com>
>> ---
>> 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               |   1 +
>>   drivers/devfreq/Makefile              |   1 +
>>   drivers/devfreq/rockchip/Kconfig      |   8 +
>>   drivers/devfreq/rockchip/Makefile     |   1 +
>>   drivers/devfreq/rockchip/rk3399_dmc.c | 473 ++++++++++++++++++++++++++++++++++
>>   5 files changed, 484 insertions(+)
>>   create mode 100644 drivers/devfreq/rockchip/Kconfig
>>   create mode 100644 drivers/devfreq/rockchip/Makefile
>>   create mode 100644 drivers/devfreq/rockchip/rk3399_dmc.c
>>
>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>> index 64281bb..acb2a57 100644
>> --- a/drivers/devfreq/Kconfig
>> +++ b/drivers/devfreq/Kconfig
>> @@ -99,5 +99,6 @@ config ARM_TEGRA_DEVFREQ
>>            operating frequencies and voltages with OPP support.
>>   
>>   source "drivers/devfreq/event/Kconfig"
>> +source "drivers/devfreq/rockchip/Kconfig"
> This patch include the only one patch. So, I think that
> you don't need to create the 'rockchip' directory.
>
>>   
>>   endif # PM_DEVFREQ
>> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
>> index 5134f9e..d844e23 100644
>> --- a/drivers/devfreq/Makefile
>> +++ b/drivers/devfreq/Makefile
>> @@ -9,6 +9,7 @@ obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
>>   obj-$(CONFIG_ARM_EXYNOS4_BUS_DEVFREQ)	+= exynos/
>>   obj-$(CONFIG_ARM_EXYNOS5_BUS_DEVFREQ)	+= exynos/
>>   obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra-devfreq.o
>> +obj-$(CONFIG_ARCH_ROCKCHIP)		+= rockchip/
> ditto.
>
>>   
>>   # DEVFREQ Event Drivers
>>   obj-$(CONFIG_PM_DEVFREQ_EVENT)		+= event/
>> diff --git a/drivers/devfreq/rockchip/Kconfig b/drivers/devfreq/rockchip/Kconfig
>> new file mode 100644
>> index 0000000..d8f9e66
>> --- /dev/null
>> +++ b/drivers/devfreq/rockchip/Kconfig
>> @@ -0,0 +1,8 @@
>> +config ARM_RK3399_DMC_DEVFREQ
>> +	tristate "ARM RK3399 DMC DEVFREQ Driver"
>> +	select PM_OPP
>> +	select DEVFREQ_GOV_SIMPLE_ONDEMAND
>> +	help
>> +          This adds the DEVFREQ driver for the RK3399 dmc. It sets the frequency
> If you add the full description for 'dmc' as following,
> it is easy to understand the operation of this device driver.
> - DMC (Dynamic Memory Controller)
>
>> +          for the memory controller and reads the usage counts from hardware.
>> +
>> diff --git a/drivers/devfreq/rockchip/Makefile b/drivers/devfreq/rockchip/Makefile
>> new file mode 100644
>> index 0000000..c62c105
>> --- /dev/null
>> +++ b/drivers/devfreq/rockchip/Makefile
>> @@ -0,0 +1 @@
>> +obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
>> diff --git a/drivers/devfreq/rockchip/rk3399_dmc.c b/drivers/devfreq/rockchip/rk3399_dmc.c
>> new file mode 100644
>> index 0000000..527aa11
>> --- /dev/null
>> +++ b/drivers/devfreq/rockchip/rk3399_dmc.c
>> @@ -0,0 +1,473 @@
>> +/*
>> + * Copyright (c) 2016, Fuzhou Rockchip Electronics Co., Ltd
> You miss the '.' at the end of the copylight.
> When you use an abbreviation, you should add '.' for Ltd.
> - s/Ltd/Ltd.
>
>
>> + * Author: Lin Huang <hl@...k-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/completion.h>
> You don't need to include the "completion.h".
> Without "completion.h", the build is working.
>
>> +#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 <linux/syscore_ops.h>
> You don't need to include the "syscore_ops.h".
> Without "syscore_ops.h", the build is working.
>
>> +
>> +#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;
>> +};
> The dram_timing is used for SMC (Secure Monitor Call)?
> I recommend that you add the detailed description about this property
> on Documentation.
>
>> +
>> +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;
>> +	wait_queue_head_t	wait_dcf_queue;
>> +	int irq;
>> +	int wait_dcf_flag;
> I want to add the full name and description of 'dcf'.
> It is unknown word.
>
>> +	struct regulator *vdd_center;
>> +	unsigned long rate, target_rate;
>> +	unsigned long volt, target_volt;
> I think that if you add 'curr_opp' variable,
> you can reduce the calling of devfreq_recommended_opp() in rk3399_dmcfreq_target()
> 	struct dev_pm_opp *curr_opp;
>
>> +};
>> +
>> +static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq,
>> +				 u32 flags)
>> +{
>> +	struct platform_device *pdev = container_of(dev, struct platform_device,
>> +						    dev);
>> +	struct rk3399_dmcfreq *dmcfreq = platform_get_drvdata(pdev);
> You can use the 'dev_get_drvdata()' to simplify it instead of 'platform_get_drvdata()'.
>
> 	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);
>> +	opp = devfreq_recommended_opp(dev, &dmcfreq->rate, flags);
>> +	if (IS_ERR(opp)) {
>> +		rcu_read_unlock();
>> +		return PTR_ERR(opp);
>> +	}
>> +	dmcfreq->volt = dev_pm_opp_get_voltage(opp);
> If you add the 'curr_opp' variable to struct rk3399_dmcfreq,
> you can remove the calling of devfreq_recommended_opp().
> 	dmcfreq->rate = dev_pm_opp_get_freq(dmcfreq->curr_opp);
> 	dmcfreq->volt = dev_pm_opp_get_freq(dmcfreq->curr_opp);
>
> Because the current rate and voltage is already decided on previous polling cycle,
> So we don't need to get the opp with devfreq_recommended_opp().
I prefer the way now use, since we get the dmcfreq->rate use 
clk_get_rate() after,
Base on that,  i do not care the set_rate success or fail. use curr_opp 
i need to
care about set_rate status, when fail, i must set some rate, when 
success i must
set other rate.
>> +	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, adjuset frequency first;
>> +	 */
> s/adjuset/adjust
>
> I recommend that you use a captital letter for first character and use the '.'
> instead of ';'.
>
>> +	if (old_clk_rate < target_rate) {
>> +		err = regulator_set_voltage(dmcfreq->vdd_center, target_volt,
>> +					    target_volt);
>> +		if (err) {
>> +			dev_err(dev, "Unable to set vol %lu\n", target_volt);
> To readability, you better to use the corrent word to pass the precise the log message.
> - s/vol/voltage
>
> And, this patch uses the 'Unable to' or 'Cannot' to show the error log.
> I recommend that you use the consistent expression if there is not any specific reason.
>
> 	dev_err(dev, "Cannot set the 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,
>> +			"Unable to set freq %lu. Current freq %lu. Error %d\n",
>> +			target_rate, old_clk_rate, err);
> 	dev_err(dev, "Cannot set the 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 bl31,
> ditto.
>
>> +	 * use 100ms as timeout time
> s/time/time.
>
>> +	 */
>> +	if (!wait_event_timeout(dmcfreq->wait_dcf_queue,
>> +				!dmcfreq->wait_dcf_flag, HZ / 10))
>> +		dev_warn(dev, "Timeout waiting for dcf irq\n");
> If the timeout happen, are there any problem?
When timeout happen , may be we miss interrupt, but it do not affect this
process, since we will check the rate whether success later.
> After setting the frequency and voltage, store the current opp entry on .curr_opp.
> 	dmcfreq->curr_opp = opp;
>
>> +	/*
>> +	 * 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 freq %lu,\
>> +			Current freq %lu\n", target_rate, dmcfreq->rate);
>> +		regulator_set_voltage(dmcfreq->vdd_center, dmcfreq->volt,
>> +				      dmcfreq->volt);
> [Without force, it is just my opion about this code:]
> I think that this checking code it is un-needed.
> If this case occur, the rk3399_dmc.c never set the specific frequency
> because the rk3399 clock don't support the specific frequency for rk3399 dmc.
>
> If you want to set the correct frequency,
> When verifying the rk3399 dmc driver, you should check the rk3399 clock driver.
>
> Basically, if the the clock driver don't support the correct same frequency ,
> CCF(Common Clock Framework) set the close frequency. It is not a bad thing.
May be i should remove the regulator_set_voltage() here, but still need to
check whether we get the right frequency, since if we do not get the 
right frequency,
we should send a warn message, to remind that maybe you pass a frequency 
which
do not support in bl31.
>
>
>> +	} else if (old_clk_rate > target_rate)
>> +		err = regulator_set_voltage(dmcfreq->vdd_center, target_volt,
>> +					    target_volt);
>> +	if (err)
>> +		dev_err(dev, "Unable to set vol %lu\n", target_volt);
> 	
> ditto. You better to use the consistent expression for error log as following:
> 	dev_err(dev, "Cannot set the voltage %lu uV\n", target_volt);
>
>
>> +
>> +out:
>> +	mutex_unlock(&dmcfreq->lock);
>> +	return err;
>> +}
>> +
>> +static int rk3399_dmcfreq_get_dev_status(struct device *dev,
>> +					 struct devfreq_dev_status *stat)
>> +{
>> +	struct platform_device *pdev = container_of(dev, struct platform_device,
>> +						    dev);
>> +	struct rk3399_dmcfreq *dmcfreq = platform_get_drvdata(pdev);
>> +	struct devfreq_event_data edata;
> ditto. Use the dev_get_drvdata(dev).
>
>> +
>> +	devfreq_event_get_event(dmcfreq->edev, &edata);
> You need to check the return value for exception handling.
>
>> +
>> +	stat->current_frequency = dmcfreq->rate;
>> +	stat->busy_time = edata.load_count;
>> +	stat->total_time = edata.total_count;
>> +
>> +	return 0;
>> +}
>> +
>> +static int rk3399_dmcfreq_get_cur_freq(struct device *dev, unsigned long *freq)
>> +{
>> +	struct platform_device *pdev = container_of(dev, struct platform_device,
>> +						    dev);
>> +	struct rk3399_dmcfreq *dmcfreq = platform_get_drvdata(pdev);
> ditto. Use the 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);
> Use the devm_devfreq_register_opp_notifier(). You don't need to handle it.
>
>> +}
>> +
>> +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 platform_device *pdev = container_of(dev,
>> +						    struct platform_device,
>> +						    dev);
>> +	struct rk3399_dmcfreq *dmcfreq = platform_get_drvdata(pdev);
> ditto. Use the dev_get_drvdata(dev).
>
>> +
>> +	devfreq_event_disable_edev(dmcfreq->edev);
>> +	devfreq_suspend_device(dmcfreq->devfreq);
> ditto. you need to check the return value.
>
>> +
>> +	return 0;
>> +}
>> +
>> +static __maybe_unused int rk3399_dmcfreq_resume(struct device *dev)
>> +{
>> +	struct platform_device *pdev = container_of(dev,
>> +						    struct platform_device,
>> +						    dev);
>> +	struct rk3399_dmcfreq *dmcfreq = platform_get_drvdata(pdev);
> ditto.
>
>> +
>> +	devfreq_event_enable_edev(dmcfreq->edev);
>> +	devfreq_resume_device(dmcfreq->devfreq);
> ditto.
>
>> +
>> +	return 0;
>> +}
>> +
>> +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);
>> +
>> +	/* clr dcf irq */
> s/ clr dcf irq -> "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 int of_do_get_timing(struct device_node *np,
>> +		struct dram_timing *timing)
>> +{
>> +	int ret;
>> +
>> +	ret = of_property_read_u32(np, "ddr3_speed_bin",
>> +				   &timing->ddr3_speed_bin);
>> +	ret |= of_property_read_u32(np, "pd_idle", &timing->pd_idle);
>> +	ret |= of_property_read_u32(np, "sr_idle", &timing->sr_idle);
>> +	ret |= of_property_read_u32(np, "sr_mc_gate_idle",
>> +				    &timing->sr_mc_gate_idle);
>> +	ret |= of_property_read_u32(np, "srpd_lite_idle",
>> +				    &timing->srpd_lite_idle);
>> +	ret |= of_property_read_u32(np, "standby_idle", &timing->standby_idle);
>> +	ret |= of_property_read_u32(np, "dram_dll_dis_freq",
>> +				    &timing->dram_dll_dis_freq);
>> +	ret |= of_property_read_u32(np, "phy_dll_dis_freq",
>> +				    &timing->phy_dll_dis_freq);
>> +	ret |= of_property_read_u32(np, "ddr3_odt_dis_freq",
>> +				    &timing->ddr3_odt_dis_freq);
>> +	ret |= of_property_read_u32(np, "ddr3_drv", &timing->ddr3_drv);
>> +	ret |= of_property_read_u32(np, "ddr3_odt", &timing->ddr3_odt);
>> +	ret |= of_property_read_u32(np, "phy_ddr3_ca_drv",
>> +				    &timing->phy_ddr3_ca_drv);
>> +	ret |= of_property_read_u32(np, "phy_ddr3_dq_drv",
>> +				    &timing->phy_ddr3_dq_drv);
>> +	ret |= of_property_read_u32(np, "phy_ddr3_odt", &timing->phy_ddr3_odt);
>> +	ret |= of_property_read_u32(np, "lpddr3_odt_dis_freq",
>> +				    &timing->lpddr3_odt_dis_freq);
>> +	ret |= of_property_read_u32(np, "lpddr3_drv", &timing->lpddr3_drv);
>> +	ret |= of_property_read_u32(np, "lpddr3_odt", &timing->lpddr3_odt);
>> +	ret |= of_property_read_u32(np, "phy_lpddr3_ca_drv",
>> +				    &timing->phy_lpddr3_ca_drv);
>> +	ret |= of_property_read_u32(np, "phy_lpddr3_dq_drv",
>> +				    &timing->phy_lpddr3_dq_drv);
>> +	ret |= of_property_read_u32(np, "phy_lpddr3_odt",
>> +				    &timing->phy_lpddr3_odt);
>> +	ret |= of_property_read_u32(np, "lpddr4_odt_dis_freq",
>> +				    &timing->lpddr4_odt_dis_freq);
>> +	ret |= of_property_read_u32(np, "lpddr4_drv",
>> +				    &timing->lpddr4_drv);
>> +	ret |= of_property_read_u32(np, "lpddr4_dq_odt",
>> +				    &timing->lpddr4_dq_odt);
>> +	ret |= of_property_read_u32(np, "lpddr4_ca_odt",
>> +				    &timing->lpddr4_ca_odt);
>> +	ret |= of_property_read_u32(np, "phy_lpddr4_ca_drv",
>> +				    &timing->phy_lpddr4_ca_drv);
>> +	ret |= of_property_read_u32(np, "phy_lpddr4_ck_cs_drv",
>> +				    &timing->phy_lpddr4_ck_cs_drv);
>> +	ret |= of_property_read_u32(np, "phy_lpddr4_dq_drv",
>> +				    &timing->phy_lpddr4_dq_drv);
>> +	ret |= of_property_read_u32(np, "phy_lpddr4_odt",
>> +				    &timing->phy_lpddr4_odt);
>> +
>> +	return ret;
>> +}
>> +
>> +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;
>> +
>> +	np_tim = of_parse_phandle(np, "ddr_timing", 0);
> As I already mentioned, you need to add the detailed documetation about the property.
>
>> +	if (np_tim) {
>> +		timing = devm_kzalloc(dev, sizeof(*timing), GFP_KERNEL);
>> +		if (!timing)
>> +			goto err;
>> +		if (of_do_get_timing(np_tim, timing)) {
> I recommend that you better to squash following two functions
> because of_do_get_timing() is not used on other point of this driver.
> - of_do_get_timing()
> - of_get_ddr_timings()
>
>> +			devm_kfree(dev, timing);
>> +			goto err;
>> +		}
> You're missing the 'of_node_put'.
> 		of_node_put(np_tim);
>
>> +		return timing;
>> +	}
>> +
>> +err:
>> +	if (timing) {
>> +		devm_kfree(dev, timing);
>> +		timing = NULL;
>> +	}
>> +
> ditto.
> 	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;
>> +	uint32_t *timing;
>> +
>> +	irq = platform_get_irq(pdev, 0);
>> +	if (irq < 0) {
>> +		dev_err(&pdev->dev, "no dmc irq resource\n");
> We need to maintain the consistent expression for error log.
> 		dev_err(&pdev->dev, ""Cannot get the 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);
> ditto. "Failed to request the dmc irq" or "Cannot request the dmc irq"
>
>> +		return ret;
>> +	}
>> +
>> +	/* get dram timing and pass it to bl31 */
> I want to add the more detailed description why this code is necessary.
> Because the SMC is usually black box. So, If you add the more explanation,
> it help people to understand this code.
>
>> +	data->timing = of_get_ddr_timings(dev, np);
>> +	if (data->timing) {
>> +		timing = (uint32_t *)data->timing;
>> +		for (index = 0; index < (sizeof(struct dram_timing) / 4);
>> +		     index++) {
> You better to use following code. It is better way to use
> the only one line for 'for' statement.
>
> 		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);
> ditto. You need to add the description.
>
>> +
>> +	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");
> s/failed/Failed. Use a capital letter for the first char.
>
>> +		return ret;
>> +	}
>> +
>> +	/*
>> +	 * We add a devfreq driver to our parent since it has a device tree node
>> +	 * with operating points.
>> +	 */
> You should wrap the rcu lock before calling the dev_pm_opp_of_add_table().
>
>> +	if (dev_pm_opp_of_add_table(dev)) {
>> +		dev_err(dev, "Invalid operating-points in device tree.\n");
>> +		return -EINVAL;
>> +	}
>> +	of_property_read_u32(np, "upthreshold",
>> +			     &data->ondemand_data.upthreshold);
>> +	of_property_read_u32(np, "downdifferential",
>> +			     &data->ondemand_data.downdifferential);
> Need one blank line.
> Maybe this code to get the properfy for ondemand governor,
> the devfreq will support in the future.
>
>> +	data->rate = clk_get_rate(data->dmc_clk);
>> +	rk3399_devfreq_dmc_profile.initial_freq = data->rate;
> Need one blank line.
>
>> +	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);
> Use the 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);
>> +	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_DESCRIPTION("RK3399 dmcfreq driver with devfreq framework");
> You need to add the MODULE_AUTHOR information.
>
> Regards,
> Chanwoo Choi
>
>
>

-- 
Lin Huang

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