Re: [PATCH 2/8] PM / devfreq: Add generic imx bus scaling driver

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

On 4/1/20 11:20 PM, Leonard Crestez wrote:
> On 2020-04-01 1:55 AM, Chanwoo Choi wrote:
>> Hi,
>>
>> Looks good to me. I added the comments.
>> But, it need to add the dt binding documentation for this device.
> 
> DT bindings were included:
> 
> https://patchwork.kernel.org/patch/11458981/

The dt-binding document for this driver is required under
Documentation/devicetree/binding/devfreq.

It is difficult to catch where is the dt-binding document
for this driver for who don't know the detailed history
of this driver. I don't said that add the duplicate documentation
But, at least the some document have to point out the reference.

> 
>> The old email of Artur Świgoń is not used. On next time,
>> use following the new email address Because when I reply the mail,
>> always show the fail message from thunderbird due to the Artur's old email.
>> <a.swigon@partnet.samsung.com> -> <a.swigon@samsung.com>
> 
> Yeah, I received multiple bounces because of this.
> 
>> On 3/26/20 11:16 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-bus.c | 142 ++++++++++++++++++++++++++++++++++++++
>>>   3 files changed, 152 insertions(+)
>>>   create mode 100644 drivers/devfreq/imx-bus.c
>>>
>>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>>> index 0b1df12e0f21..44d26192ddc4 100644
>>> --- a/drivers/devfreq/Kconfig
>>> +++ b/drivers/devfreq/Kconfig
>>> @@ -99,10 +99,19 @@ 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_BUS_DEVFREQ
>>> +	tristate "i.MX Generic Bus DEVFREQ Driver"
>>> +	depends on ARCH_MXC || COMPILE_TEST
>>> +	select DEVFREQ_GOV_PASSIVE
>>> +	select DEVFREQ_GOV_USERSPACE
>>
>> Maybe, you would update it by using passive governor?
>> But, in this version, it doesn't handle the any passive governor.
> 
> dropped
> 
>>> +	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..3ca1ad0ecb97 100644
>>> --- a/drivers/devfreq/Makefile
>>> +++ b/drivers/devfreq/Makefile
>>> @@ -7,10 +7,11 @@ obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)	+= governor_powersave.o
>>>   obj-$(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-$(CONFIG_ARM_IMX_BUS_DEVFREQ)	+= imx-bus.o
>>
>> The ARM_IMX_BUS_DEVFREQ config is under ARM_IMX8M_DDRC_DEVFREQ
>> and imx-bus.o is over imx8m-ddrc.o. Need to edit the sequence.
> 
> Reordered kconfig to match. 8M_DDRC sorts before _BUS alphabetically but 
> it's pettier this way, and matches tegra.
> 
>>>   obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ)	+= imx8m-ddrc.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
>>>   
>>> diff --git a/drivers/devfreq/imx-bus.c b/drivers/devfreq/imx-bus.c
>>> new file mode 100644
>>> index 000000000000..285e0f1ae6b1
>>> --- /dev/null
>>> +++ b/drivers/devfreq/imx-bus.c
>>> @@ -0,0 +1,142 @@
>>> +// 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_bus {
>>> +	struct devfreq_dev_profile profile;
>>> +	struct devfreq *devfreq;
>>> +	struct clk *clk;
>>> +	struct devfreq_passive_data passive_data;
>>
>> This patch doesn't touch the passive_data.
> 
> dropped
> 
>>> +};
>>> +
>>> +static int imx_bus_target(struct device *dev,
>>> +		unsigned long *freq, u32 flags)
>>> +{
>>> +	struct imx_bus *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);
>>
>> It doesn't need. Because the new frequency is stored to 'freq'
>> by calling devfreq_recommended_opp().
> 
> fixed
> 
>>> +	dev_pm_opp_put(new_opp);
>>> +
>>> +	return clk_set_rate(priv->clk, new_freq);
>>
>> nitpick. you can use dev_pm_opp_set_rate(). But, I'm not forcing to use it.
> 
> Switched to dev_pm_opp_set_rate.
> 
> It might be interesting to add regulators control later, on some chips 
> the main NOC can run at different voltages.
> 
>>
>>> +}
>>> +
>>> +static int imx_bus_get_cur_freq(struct device *dev, unsigned long *freq)
>>> +{
>>> +	struct imx_bus *priv = dev_get_drvdata(dev);
>>> +
>>> +	*freq = clk_get_rate(priv->clk);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int imx_bus_get_dev_status(struct device *dev,
>>> +		struct devfreq_dev_status *stat)
>>> +{
>>> +	struct imx_bus *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_bus_exit(struct device *dev)
>>> +{
>>> +	dev_pm_opp_of_remove_table(dev);
>>> +}
>>> +
>>> +static int imx_bus_probe(struct platform_device *pdev)
>>> +{
>>> +	struct device *dev = &pdev->dev;
>>> +	struct imx_bus *priv;
>>> +	const char *gov = DEVFREQ_GOV_USERSPACE;
>>> +	int ret;
>>> +
>>> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>>> +	if (!priv)
>>> +		return -ENOMEM;
>>> +
>>> +	/*
>>> +	 * Fetch the clock to adjust but don't explictly enable.
>>
>> Need to fix typo.
>> s/explictly/explicitly
> 
> fixed
> 
>>> +	 *
>>> +	 * For imx bus clock clk_set_rate is safe no matter if the clock is on
>>> +	 * or off and some peripheral side-buses might be off unless enabled by
>>> +	 * drivers for devices on those specific buses.
>>> +	 *
>>> +	 * Rate adjustment on a disabled bus clock just takes effect later.
>>> +	 */
>>> +	priv->clk = devm_clk_get(dev, NULL);
>>> +	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_bus_target;
>>> +	priv->profile.get_dev_status = imx_bus_get_dev_status;
>>> +	priv->profile.exit = imx_bus_exit;
>>> +	priv->profile.get_cur_freq = imx_bus_get_cur_freq;
>>> +	priv->profile.initial_freq = clk_get_rate(priv->clk);
>>> +
>>> +	priv->devfreq = devm_devfreq_add_device(dev, &priv->profile,
>>> +						gov, NULL);
>>> +	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_bus_of_match[] = {
>>> +	{ .compatible = "fsl,imx8m-noc", },
>>> +	{ .compatible = "fsl,imx8m-nic", },
>>> +	{ /* sentinel */ },
>>> +};
>>> +MODULE_DEVICE_TABLE(of, imx_bus_of_match);
>>> +
>>> +static struct platform_driver imx_bus_platdrv = {
>>> +	.probe		= imx_bus_probe,
>>> +	.driver = {
>>> +		.name	= "imx-bus-devfreq",
>>> +		.of_match_table = of_match_ptr(imx_bus_of_match),
>>> +	},
>>> +};
>>> +module_platform_driver(imx_bus_platdrv);
>>> +
>>> +MODULE_DESCRIPTION("Generic i.MX bus frequency scaling driver");
>>> +MODULE_AUTHOR("Leonard Crestez <leonard.crestez@nxp.com>");
>>> +MODULE_LICENSE("GPL v2");
>>>
>>
>>
> 
> 
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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