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

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

On 4/2/20 6:53 PM, Leonard Crestez wrote:
> On 2020-04-02 1:48 AM, Chanwoo Choi wrote:
>> 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://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fpatch%2F11458981%2F&data=02%7C01%7Cleonard.crestez%40nxp.com%7C7381d117a4d1468cd2c608d7d68ecfac%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637213781167514099&sdata=Qu8x14cXnuxlwOT2SlUOf%2FLgCVWbnJRKA4TBjMIWQeA%3D&reserved=0
>>
>> The dt-binding document for this driver is required under
>> Documentation/devicetree/binding/devfreq.
> 
> Bindings for imx8m-ddrc were at one point posted for 
> devicetree/bindings/devfreq but Rob Herring suggested to move them under 
> "memory-controller" instead and I expect same logic makes sense here. 
> Link to previous discussion:
> 
> https://patchwork.kernel.org/patch/11221919/
> 
> DT bindings should try to describe "hardware" rather than "drivers" and 
> an "interconnect" is a class of hardware while "devfreq" isn't.
> 
> Not only that but the main noc has properties parsed by interconnect driver.

OK. Thanks for reply.

> 
>> 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.
> 
> What I usually do to find information about a device is grep for the 
> compat string in the entire tree.
> 
>>>> 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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