Re: [PATCH RFC v6 2/9] PM / devfreq: Add generic imx bus scaling driver

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

On 12/13/19 10:30 AM, Chanwoo Choi wrote:
> Hi,
> 
> On 11/15/19 5:09 AM, Leonard Crestez wrote:
>> Add initial support for dynamic frequency switching on pieces of the imx
>> interconnect fabric.
>>
>> All this driver does is set a clk rate based on an opp table, it does
>> not map register areas.
>>
>> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
>> ---
>>  drivers/devfreq/Kconfig       |   9 ++
>>  drivers/devfreq/Makefile      |   1 +
>>  drivers/devfreq/imx-devfreq.c | 150 ++++++++++++++++++++++++++++++++++
>>  3 files changed, 160 insertions(+)
>>  create mode 100644 drivers/devfreq/imx-devfreq.c
>>
>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>> index 923a6132e741..fef5ce831e90 100644
>> --- a/drivers/devfreq/Kconfig
>> +++ b/drivers/devfreq/Kconfig
>> @@ -98,10 +98,19 @@ config ARM_IMX8M_DDRC_DEVFREQ
>>  	select DEVFREQ_GOV_USERSPACE
>>  	help
>>  	  This adds the DEVFREQ driver for the i.MX8M DDR Controller. It allows
>>  	  adjusting DRAM frequency.
>>  
>> +config ARM_IMX_DEVFREQ
>> +	tristate "i.MX Generic DEVFREQ Driver"
>> +	depends on ARCH_MXC || COMPILE_TEST
>> +	select DEVFREQ_GOV_PASSIVE
>> +	select DEVFREQ_GOV_USERSPACE
>> +	help
>> +	  This adds the generic DEVFREQ driver for i.MX interconnects. It
>> +	  allows adjusting NIC/NOC frequency.
>> +
>>  config ARM_TEGRA_DEVFREQ
>>  	tristate "NVIDIA Tegra30/114/124/210 DEVFREQ Driver"
>>  	depends on ARCH_TEGRA_3x_SOC || ARCH_TEGRA_114_SOC || \
>>  		ARCH_TEGRA_132_SOC || ARCH_TEGRA_124_SOC || \
>>  		ARCH_TEGRA_210_SOC || \
>> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
>> index 3eb4d5e6635c..61d0edee16f7 100644
>> --- a/drivers/devfreq/Makefile
>> +++ b/drivers/devfreq/Makefile
>> @@ -8,10 +8,11 @@ obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
>>  obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
>>  
>>  # DEVFREQ Drivers
>>  obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
>>  obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ)	+= imx8m-ddrc.o
>> +obj-$(CONFIG_ARM_IMX_DEVFREQ)		+= imx-devfreq.o
>>  obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
>>  obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra30-devfreq.o
>>  obj-$(CONFIG_ARM_TEGRA20_DEVFREQ)	+= tegra20-devfreq.o
>>  
>>  # DEVFREQ Event Drivers
>> diff --git a/drivers/devfreq/imx-devfreq.c b/drivers/devfreq/imx-devfreq.c
>> new file mode 100644
>> index 000000000000..620b344e87aa
>> --- /dev/null
>> +++ b/drivers/devfreq/imx-devfreq.c
>> @@ -0,0 +1,150 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright 2019 NXP
>> + */
>> +
>> +#include <linux/clk.h>
>> +#include <linux/devfreq.h>
>> +#include <linux/device.h>
>> +#include <linux/module.h>
>> +#include <linux/of_device.h>
>> +#include <linux/pm_opp.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/slab.h>
>> +
>> +struct imx_devfreq {
>> +	struct devfreq_dev_profile profile;
>> +	struct devfreq *devfreq;
>> +	struct clk *clk;
>> +	struct devfreq_passive_data passive_data;
>> +};
>> +
>> +static int imx_devfreq_target(struct device *dev,
>> +			      unsigned long *freq, u32 flags)
> 
> Don't use space for the indentation. Please use only tab.
> 
>> +{
>> +	struct imx_devfreq *priv = dev_get_drvdata(dev);
>> +	struct dev_pm_opp *new_opp;
>> +	unsigned long new_freq;
>> +	int ret;
>> +
>> +	new_opp = devfreq_recommended_opp(dev, freq, flags);
>> +	if (IS_ERR(new_opp)) {
>> +		ret = PTR_ERR(new_opp);
>> +		dev_err(dev, "failed to get recommended opp: %d\n", ret);
>> +		return ret;
>> +	}
>> +	new_freq = dev_pm_opp_get_freq(new_opp);
>> +	dev_pm_opp_put(new_opp);
>> +
>> +	return clk_set_rate(priv->clk, new_freq);
>> +}
>> +
>> +static int imx_devfreq_get_cur_freq(struct device *dev, unsigned long *freq)
>> +{
>> +	struct imx_devfreq *priv = dev_get_drvdata(dev);
>> +
>> +	*freq = clk_get_rate(priv->clk);
>> +
>> +	return 0;
>> +}
>> +
>> +static int imx_devfreq_get_dev_status(struct device *dev,
>> +				      struct devfreq_dev_status *stat)
> 
> ditto. Please use tab for the indentation.
> 
>> +{
>> +	struct imx_devfreq *priv = dev_get_drvdata(dev);
>> +
>> +	stat->busy_time = 0;
>> +	stat->total_time = 0;
>> +	stat->current_frequency = clk_get_rate(priv->clk);
>> +
>> +	return 0;
>> +}
>> +
>> +static void imx_devfreq_exit(struct device *dev)
>> +{
>> +	dev_pm_opp_of_remove_table(dev);
>> +}
>> +
>> +static int imx_devfreq_probe(struct platform_device *pdev)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	struct imx_devfreq *priv;
> 
> How about changing the variable name 'priv' to 'imx' or 'imx_data'?
> because it is not easy to catch the role of 'priv' from variable name.
> 
>> +	const char *gov = DEVFREQ_GOV_USERSPACE;
>> +	void *govdata = NULL;
> 
> How about changing the variable name 'govdata' to 'gov_data'?
> - govdata -> gov_data
> 
>> +	int ret;
>> +
>> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>> +	if (!priv)
>> +		return -ENOMEM;
>> +
>> +	priv->clk = devm_clk_get(dev, NULL);
> 
> nitpick: because the clock-name is not mandatory.
> Don't need to specify the clock name to inform the role of clock
> of other developer/user?
> 
> For example, "ddr", "bus" and so on.

And, this driver doesn't include the 'clk_prepare_enable'.
how to enable the clock?

> 
>> +	if (IS_ERR(priv->clk)) {
>> +		ret = PTR_ERR(priv->clk);
>> +		dev_err(dev, "failed to fetch clk: %d\n", ret);
>> +		return ret;
>> +	}
>> +	platform_set_drvdata(pdev, priv);
>> +
>> +	ret = dev_pm_opp_of_add_table(dev);
>> +	if (ret < 0) {
>> +		dev_err(dev, "failed to get OPP table\n");
>> +		return ret;
>> +	}
>> +
>> +	priv->profile.polling_ms = 1000;
>> +	priv->profile.target = imx_devfreq_target;
>> +	priv->profile.get_dev_status = imx_devfreq_get_dev_status;
>> +	priv->profile.exit = imx_devfreq_exit;
>> +	priv->profile.get_cur_freq = imx_devfreq_get_cur_freq;
>> +	priv->profile.initial_freq = clk_get_rate(priv->clk);
>> +
>> +	/* Handle passive devfreq parent link */
>> +	priv->passive_data.parent = devfreq_get_devfreq_by_phandle(dev, 0);
>> +	if (!IS_ERR(priv->passive_data.parent)) {
>> +		dev_info(dev, "setup passive link to %s\n",
>> +			 dev_name(priv->passive_data.parent->dev.parent));
>> +		gov = DEVFREQ_GOV_PASSIVE;
>> +		govdata = &priv->passive_data;
>> +	} else if (priv->passive_data.parent != ERR_PTR(-ENODEV)) {
>> +		// -ENODEV means no parent: not an error.
>> +		ret = PTR_ERR(priv->passive_data.parent);
>> +		if (ret != -EPROBE_DEFER)
>> +			dev_warn(dev, "failed to get initialize passive parent: %d\n",
>> +				 ret);
>> +		goto err;
>> +	}
> 
> You better to change the exception handling as following: It is more simple.
> 
> 	} else if (PTR_ERR(priv->passive_data.parent) == -EPROBE_DEFER)
> 			|| PTR_ERR(priv->passive_data.parent) == -ENODEV) {
> 		goto err;
> 	} else {
> 		ret = PTR_ERR(priv->passive_data.parent);
> 		dev_err(dev, "failed to get initialize passive parent: %d\n", ret);
> 		goto err;
> 	}
> 
>> +
>> +	priv->devfreq = devm_devfreq_add_device(dev, &priv->profile,
>> +						gov, govdata);
>> +	if (IS_ERR(priv->devfreq)) {
>> +		ret = PTR_ERR(priv->devfreq);
>> +		dev_err(dev, "failed to add devfreq device: %d\n", ret);
>> +		goto err;
>> +	}
>> +
>> +	return 0;
>> +
>> +err:
>> +	dev_pm_opp_of_remove_table(dev);
>> +	return ret;
>> +}
>> +
>> +static const struct of_device_id imx_devfreq_of_match[] = {
>> +	{ .compatible = "fsl,imx8m-noc", },
>> +	{ .compatible = "fsl,imx8m-nic", },
>> +	{ /* sentinel */ },
>> +};
>> +MODULE_DEVICE_TABLE(of, imx_devfreq_of_match);
>> +
>> +static struct platform_driver imx_devfreq_platdrv = {
>> +	.probe		= imx_devfreq_probe,
>> +	.driver = {
>> +		.name	= "imx-devfreq",
>> +		.of_match_table = of_match_ptr(imx_devfreq_of_match),
>> +	},
>> +};
>> +module_platform_driver(imx_devfreq_platdrv);
>> +
>> +MODULE_DESCRIPTION("Generic i.MX bus frequency driver");
> 
> If this driver is for bus frequency, you better to use 'bus' for the clock-name
> for the readability.
> 
>> +MODULE_AUTHOR("Leonard Crestez <leonard.crestez@nxp.com>");
>> +MODULE_LICENSE("GPL v2");
>>
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics