Re: [PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

Re: [PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

[MyungJoo Ham]

>   
>  This patch adds the generic exynos bus frequency driver for memory bus
> with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
> for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
> support the memory bus frequency driver for Exynos SoCs.
> 
> Each memory bus block has a clock for memory bus speed and frequency
> table which is changed according to the utilization of memory bus on runtime.
> And then each memory bus group has the one more memory bus blocks and
> OPP table (including frequency and voltage), regulator, devfreq-event
> devices.
> 
> There are a little difference about the number of memory bus because each Exynos
> SoC have the different sub-IP and different memory bus speed. In spite of this
> difference among Exynos SoCs, we can support almost Exynos SoC by adding
> unique data of memory bus to devicetree file.
> 
> Cc: Myungjoo Ham <myungjoo.ham@samsung.com>
> Cc: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: Kukjin Kim <kgene@kernel.org>
> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
> ---
>  drivers/devfreq/Kconfig          |  15 +
>  drivers/devfreq/Makefile         |   1 +
>  drivers/devfreq/exynos-busfreq.c | 589 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 605 insertions(+)
>  create mode 100644 drivers/devfreq/exynos-busfreq.c

Exynos drivers are located at drivers/devfreq/exynos/
Please relocate/rename exynos-busfreq.c

[]

> diff --git a/drivers/devfreq/exynos-busfreq.c b/drivers/devfreq/exynos-busfreq.c
> new file mode 100644
> index 0000000..b180f43
> --- /dev/null
> +++ b/drivers/devfreq/exynos-busfreq.c

[]

> +
> +#define BUS_SATURATION_RATIO	40

In order to be a common driver, this should be tunable.

Because .dts is supposed to have hardware configuration only,
you may keep a table of { chip-name, saturation ratio} in this
driver and look up the saturation ratio based on the chip-name.

> +#define SAFEVOLT		50000
> +
> +struct exynos_memory_bus_opp_info {
> +	unsigned long rate;
> +	unsigned long volt;
> +};
> +
> +struct exynos_memory_bus_block {
> +	struct clk *clk;
> +	struct exynos_memory_bus_opp_info *freq_table;
> +};
> +

[]

> +#ifdef CONFIG_PM_SLEEP
> +static int exynos_busfreq_resume(struct device *dev)
> +{
> +	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = exynos_busfreq_enable_edev(data);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to enable the devfreq-event devices\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int exynos_busfreq_suspend(struct device *dev)
> +{
> +	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = exynos_busfreq_disable_edev(data);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to disable the devfreq-event devices\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +#endif

Please disable regulator at suspend and resume it at resume.

You may interfere with low-power mode of corresponding voltage line,
which is often implemented to be activated if the regulator is
explicitely disabled for "alive" regulators like this one.

> +
> +static const struct dev_pm_ops exynos_busfreq_pm = {
> +	SET_SYSTEM_SLEEP_PM_OPS(exynos_busfreq_suspend, exynos_busfreq_resume)
> +};
> +
> +static const struct of_device_id exynos_busfreq_of_match[] = {
> +	{ .compatible = "samsung,exynos-memory-bus", },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, exynos_busfreq_of_match);
> +
> +static struct platform_driver exynos_busfreq_platdrv = {
> +	.probe		= exynos_busfreq_probe,
> +	.remove		= exynos_busfreq_remove,
> +	.driver = {
> +		.name	= "exynos-memory-bus",
> +		.owner	= THIS_MODULE,
> +		.pm	= &exynos_busfreq_pm,
> +		.of_match_table = of_match_ptr(exynos_busfreq_of_match),
> +	},
> +};
> +module_platform_driver(exynos_busfreq_platdrv);
> +
> +MODULE_DESCRIPTION("Generic Exynos Memory Bus Frequency driver");
> +MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
> +MODULE_LICENSE("GPL v2");
> -- 
> 1.8.5.5
> 
> 

Re: [PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

[MyungJoo Ham]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=utf-8, Size: 4173 bytes --]

>   
>  This patch adds the generic exynos bus frequency driver for memory bus
> with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
> for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
> support the memory bus frequency driver for Exynos SoCs.
> 
> Each memory bus block has a clock for memory bus speed and frequency
> table which is changed according to the utilization of memory bus on runtime.
> And then each memory bus group has the one more memory bus blocks and
> OPP table (including frequency and voltage), regulator, devfreq-event
> devices.
> 
> There are a little difference about the number of memory bus because each Exynos
> SoC have the different sub-IP and different memory bus speed. In spite of this
> difference among Exynos SoCs, we can support almost Exynos SoC by adding
> unique data of memory bus to devicetree file.
> 
> Cc: Myungjoo Ham <myungjoo.ham@samsung.com>
> Cc: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: Kukjin Kim <kgene@kernel.org>
> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
> ---
>  drivers/devfreq/Kconfig          |  15 +
>  drivers/devfreq/Makefile         |   1 +
>  drivers/devfreq/exynos-busfreq.c | 589 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 605 insertions(+)
>  create mode 100644 drivers/devfreq/exynos-busfreq.c

Exynos drivers are located at drivers/devfreq/exynos/
Please relocate/rename exynos-busfreq.c

[]

> diff --git a/drivers/devfreq/exynos-busfreq.c b/drivers/devfreq/exynos-busfreq.c
> new file mode 100644
> index 0000000..b180f43
> --- /dev/null
> +++ b/drivers/devfreq/exynos-busfreq.c

[]

> +
> +#define BUS_SATURATION_RATIO	40

In order to be a common driver, this should be tunable.

Because .dts is supposed to have hardware configuration only,
you may keep a table of { chip-name, saturation ratio} in this
driver and look up the saturation ratio based on the chip-name.

> +#define SAFEVOLT		50000
> +
> +struct exynos_memory_bus_opp_info {
> +	unsigned long rate;
> +	unsigned long volt;
> +};
> +
> +struct exynos_memory_bus_block {
> +	struct clk *clk;
> +	struct exynos_memory_bus_opp_info *freq_table;
> +};
> +

[]

> +#ifdef CONFIG_PM_SLEEP
> +static int exynos_busfreq_resume(struct device *dev)
> +{
> +	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = exynos_busfreq_enable_edev(data);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to enable the devfreq-event devices\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int exynos_busfreq_suspend(struct device *dev)
> +{
> +	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = exynos_busfreq_disable_edev(data);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to disable the devfreq-event devices\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +#endif

Please disable regulator at suspend and resume it at resume.

You may interfere with low-power mode of corresponding voltage line,
which is often implemented to be activated if the regulator is
explicitely disabled for "alive" regulators like this one.

> +
> +static const struct dev_pm_ops exynos_busfreq_pm = {
> +	SET_SYSTEM_SLEEP_PM_OPS(exynos_busfreq_suspend, exynos_busfreq_resume)
> +};
> +
> +static const struct of_device_id exynos_busfreq_of_match[] = {
> +	{ .compatible = "samsung,exynos-memory-bus", },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, exynos_busfreq_of_match);
> +
> +static struct platform_driver exynos_busfreq_platdrv = {
> +	.probe		= exynos_busfreq_probe,
> +	.remove		= exynos_busfreq_remove,
> +	.driver = {
> +		.name	= "exynos-memory-bus",
> +		.owner	= THIS_MODULE,
> +		.pm	= &exynos_busfreq_pm,
> +		.of_match_table = of_match_ptr(exynos_busfreq_of_match),
> +	},
> +};
> +module_platform_driver(exynos_busfreq_platdrv);
> +
> +MODULE_DESCRIPTION("Generic Exynos Memory Bus Frequency driver");
> +MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
> +MODULE_LICENSE("GPL v2");
> -- 
> 1.8.5.5
> 
> 
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Re: [PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

[Chanwoo Choi]

Dear Myungjoo,

On 01/13/2015 05:42 PM, MyungJoo Ham wrote:
>>   
>>  This patch adds the generic exynos bus frequency driver for memory bus
>> with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
>> for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
>> support the memory bus frequency driver for Exynos SoCs.
>>
>> Each memory bus block has a clock for memory bus speed and frequency
>> table which is changed according to the utilization of memory bus on runtime.
>> And then each memory bus group has the one more memory bus blocks and
>> OPP table (including frequency and voltage), regulator, devfreq-event
>> devices.
>>
>> There are a little difference about the number of memory bus because each Exynos
>> SoC have the different sub-IP and different memory bus speed. In spite of this
>> difference among Exynos SoCs, we can support almost Exynos SoC by adding
>> unique data of memory bus to devicetree file.
>>
>> Cc: Myungjoo Ham <myungjoo.ham@samsung.com>
>> Cc: Kyungmin Park <kyungmin.park@samsung.com>
>> Cc: Kukjin Kim <kgene@kernel.org>
>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>> ---
>>  drivers/devfreq/Kconfig          |  15 +
>>  drivers/devfreq/Makefile         |   1 +
>>  drivers/devfreq/exynos-busfreq.c | 589 +++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 605 insertions(+)
>>  create mode 100644 drivers/devfreq/exynos-busfreq.c
> 
> Exynos drivers are located at drivers/devfreq/exynos/
> Please relocate/rename exynos-busfreq.c

OK. I'll move it at drivers/devfreq/exynos directory.
Do you prefer 'exynos-bus.c' instead of 'exynos-busfreq.c'?
If you reply, I'll change it.

> 
> []
> 
>> diff --git a/drivers/devfreq/exynos-busfreq.c b/drivers/devfreq/exynos-busfreq.c
>> new file mode 100644
>> index 0000000..b180f43
>> --- /dev/null
>> +++ b/drivers/devfreq/exynos-busfreq.c
> 
> []
> 
>> +
>> +#define BUS_SATURATION_RATIO	40
> 
> In order to be a common driver, this should be tunable.
> 
> Because .dts is supposed to have hardware configuration only,
> you may keep a table of { chip-name, saturation ratio} in this
> driver and look up the saturation ratio based on the chip-name.

OK, I'll add new property for saturation_ratio.

I'll implement to use default saturation_ratio value ,
if dt node don't include saturation_ratio property.

> 
>> +#define SAFEVOLT		50000
>> +
>> +struct exynos_memory_bus_opp_info {
>> +	unsigned long rate;
>> +	unsigned long volt;
>> +};
>> +
>> +struct exynos_memory_bus_block {
>> +	struct clk *clk;
>> +	struct exynos_memory_bus_opp_info *freq_table;
>> +};
>> +
> 
> []
> 
>> +#ifdef CONFIG_PM_SLEEP
>> +static int exynos_busfreq_resume(struct device *dev)
>> +{
>> +	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
>> +	int ret;
>> +
>> +	ret = exynos_busfreq_enable_edev(data);
>> +	if (ret < 0) {
>> +		dev_err(dev, "failed to enable the devfreq-event devices\n");
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int exynos_busfreq_suspend(struct device *dev)
>> +{
>> +	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
>> +	int ret;
>> +
>> +	ret = exynos_busfreq_disable_edev(data);
>> +	if (ret < 0) {
>> +		dev_err(dev, "failed to disable the devfreq-event devices\n");
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +#endif
> 
> Please disable regulator at suspend and resume it at resume.
> 
> You may interfere with low-power mode of corresponding voltage line,
> which is often implemented to be activated if the regulator is
> explicitely disabled for "alive" regulators like this one.

OK, I'll modify it.

Thanks for your review.

Best Regards,
Chanwoo Choi

[PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

[Chanwoo Choi]

Dear Myungjoo,

On 01/13/2015 05:42 PM, MyungJoo Ham wrote:
>>   
>>  This patch adds the generic exynos bus frequency driver for memory bus
>> with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
>> for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
>> support the memory bus frequency driver for Exynos SoCs.
>>
>> Each memory bus block has a clock for memory bus speed and frequency
>> table which is changed according to the utilization of memory bus on runtime.
>> And then each memory bus group has the one more memory bus blocks and
>> OPP table (including frequency and voltage), regulator, devfreq-event
>> devices.
>>
>> There are a little difference about the number of memory bus because each Exynos
>> SoC have the different sub-IP and different memory bus speed. In spite of this
>> difference among Exynos SoCs, we can support almost Exynos SoC by adding
>> unique data of memory bus to devicetree file.
>>
>> Cc: Myungjoo Ham <myungjoo.ham@samsung.com>
>> Cc: Kyungmin Park <kyungmin.park@samsung.com>
>> Cc: Kukjin Kim <kgene@kernel.org>
>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>> ---
>>  drivers/devfreq/Kconfig          |  15 +
>>  drivers/devfreq/Makefile         |   1 +
>>  drivers/devfreq/exynos-busfreq.c | 589 +++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 605 insertions(+)
>>  create mode 100644 drivers/devfreq/exynos-busfreq.c
> 
> Exynos drivers are located at drivers/devfreq/exynos/
> Please relocate/rename exynos-busfreq.c

OK. I'll move it at drivers/devfreq/exynos directory.
Do you prefer 'exynos-bus.c' instead of 'exynos-busfreq.c'?
If you reply, I'll change it.

> 
> []
> 
>> diff --git a/drivers/devfreq/exynos-busfreq.c b/drivers/devfreq/exynos-busfreq.c
>> new file mode 100644
>> index 0000000..b180f43
>> --- /dev/null
>> +++ b/drivers/devfreq/exynos-busfreq.c
> 
> []
> 
>> +
>> +#define BUS_SATURATION_RATIO	40
> 
> In order to be a common driver, this should be tunable.
> 
> Because .dts is supposed to have hardware configuration only,
> you may keep a table of { chip-name, saturation ratio} in this
> driver and look up the saturation ratio based on the chip-name.

OK, I'll add new property for saturation_ratio.

I'll implement to use default saturation_ratio value ,
if dt node don't include saturation_ratio property.

> 
>> +#define SAFEVOLT		50000
>> +
>> +struct exynos_memory_bus_opp_info {
>> +	unsigned long rate;
>> +	unsigned long volt;
>> +};
>> +
>> +struct exynos_memory_bus_block {
>> +	struct clk *clk;
>> +	struct exynos_memory_bus_opp_info *freq_table;
>> +};
>> +
> 
> []
> 
>> +#ifdef CONFIG_PM_SLEEP
>> +static int exynos_busfreq_resume(struct device *dev)
>> +{
>> +	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
>> +	int ret;
>> +
>> +	ret = exynos_busfreq_enable_edev(data);
>> +	if (ret < 0) {
>> +		dev_err(dev, "failed to enable the devfreq-event devices\n");
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int exynos_busfreq_suspend(struct device *dev)
>> +{
>> +	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
>> +	int ret;
>> +
>> +	ret = exynos_busfreq_disable_edev(data);
>> +	if (ret < 0) {
>> +		dev_err(dev, "failed to disable the devfreq-event devices\n");
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +#endif
> 
> Please disable regulator at suspend and resume it at resume.
> 
> You may interfere with low-power mode of corresponding voltage line,
> which is often implemented to be activated if the regulator is
> explicitely disabled for "alive" regulators like this one.

OK, I'll modify it.

Thanks for your review.

Best Regards,
Chanwoo Choi

Re: Re: [PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

[MyungJoo Ham]

>  
> Dear Myungjoo,
>
>On 01/13/2015 05:42 PM, MyungJoo Ham wrote:
>>>   
>>>  This patch adds the generic exynos bus frequency driver for memory bus
>>> with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
>>> for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
>>> support the memory bus frequency driver for Exynos SoCs.
>>>
>>> Each memory bus block has a clock for memory bus speed and frequency
>>> table which is changed according to the utilization of memory bus on runtime.
>>> And then each memory bus group has the one more memory bus blocks and
>>> OPP table (including frequency and voltage), regulator, devfreq-event
>>> devices.
>>>
>>> There are a little difference about the number of memory bus because each Exynos
>>> SoC have the different sub-IP and different memory bus speed. In spite of this
>>> difference among Exynos SoCs, we can support almost Exynos SoC by adding
>>> unique data of memory bus to devicetree file.
>>>
>>> Cc: Myungjoo Ham <myungjoo.ham@samsung.com>
>>> Cc: Kyungmin Park <kyungmin.park@samsung.com>
>>> Cc: Kukjin Kim <kgene@kernel.org>
>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>>> ---
>>>  drivers/devfreq/Kconfig          |  15 +
>>>  drivers/devfreq/Makefile         |   1 +
>>>  drivers/devfreq/exynos-busfreq.c | 589 +++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 605 insertions(+)
>>>  create mode 100644 drivers/devfreq/exynos-busfreq.c
>> 
>> Exynos drivers are located at drivers/devfreq/exynos/
>> Please relocate/rename exynos-busfreq.c
>
>OK. I'll move it at drivers/devfreq/exynos directory.
>Do you prefer 'exynos-bus.c' instead of 'exynos-busfreq.c'?
>If you reply, I'll change it.

exynos-bus looks more pretty :)

>
>> 
>> []
>> 
>>> diff --git a/drivers/devfreq/exynos-busfreq.c b/drivers/devfreq/exynos-busfreq.c
>>> new file mode 100644
>>> index 0000000..b180f43
>>> --- /dev/null
>>> +++ b/drivers/devfreq/exynos-busfreq.c
>> 
>> []
>> 
>>> +
>>> +#define BUS_SATURATION_RATIO	40
>> 
>> In order to be a common driver, this should be tunable.
>> 
>> Because .dts is supposed to have hardware configuration only,
>> you may keep a table of { chip-name, saturation ratio} in this
>> driver and look up the saturation ratio based on the chip-name.
>
>OK, I'll add new property for saturation_ratio.
>
>I'll implement to use default saturation_ratio value ,
>if dt node don't include saturation_ratio property.

Yes. I didn't talk with DT maintainers and I do not have much
experience with DT; however, it appears that such values are not
recommended to be in DTS files and this value is determined by
the SoC model number without complications in the driver file.

Re: [PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

[Chanwoo Choi]

On 01/13/2015 06:07 PM, MyungJoo Ham wrote:
>>  
>> Dear Myungjoo,
>>
>> On 01/13/2015 05:42 PM, MyungJoo Ham wrote:
>>>>   
>>>>  This patch adds the generic exynos bus frequency driver for memory bus
>>>> with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
>>>> for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
>>>> support the memory bus frequency driver for Exynos SoCs.
>>>>
>>>> Each memory bus block has a clock for memory bus speed and frequency
>>>> table which is changed according to the utilization of memory bus on runtime.
>>>> And then each memory bus group has the one more memory bus blocks and
>>>> OPP table (including frequency and voltage), regulator, devfreq-event
>>>> devices.
>>>>
>>>> There are a little difference about the number of memory bus because each Exynos
>>>> SoC have the different sub-IP and different memory bus speed. In spite of this
>>>> difference among Exynos SoCs, we can support almost Exynos SoC by adding
>>>> unique data of memory bus to devicetree file.
>>>>
>>>> Cc: Myungjoo Ham <myungjoo.ham@samsung.com>
>>>> Cc: Kyungmin Park <kyungmin.park@samsung.com>
>>>> Cc: Kukjin Kim <kgene@kernel.org>
>>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>>>> ---
>>>>  drivers/devfreq/Kconfig          |  15 +
>>>>  drivers/devfreq/Makefile         |   1 +
>>>>  drivers/devfreq/exynos-busfreq.c | 589 +++++++++++++++++++++++++++++++++++++++
>>>>  3 files changed, 605 insertions(+)
>>>>  create mode 100644 drivers/devfreq/exynos-busfreq.c
>>>
>>> Exynos drivers are located at drivers/devfreq/exynos/
>>> Please relocate/rename exynos-busfreq.c
>>
>> OK. I'll move it at drivers/devfreq/exynos directory.
>> Do you prefer 'exynos-bus.c' instead of 'exynos-busfreq.c'?
>> If you reply, I'll change it.
> 
> exynos-bus looks more pretty :)

OK, I'll change the driver name according to your comment.

Best Regards,
Chanwoo Choi

> 
>>
>>>
>>> []
>>>
>>>> diff --git a/drivers/devfreq/exynos-busfreq.c b/drivers/devfreq/exynos-busfreq.c
>>>> new file mode 100644
>>>> index 0000000..b180f43
>>>> --- /dev/null
>>>> +++ b/drivers/devfreq/exynos-busfreq.c
>>>
>>> []
>>>
>>>> +
>>>> +#define BUS_SATURATION_RATIO	40
>>>
>>> In order to be a common driver, this should be tunable.
>>>
>>> Because .dts is supposed to have hardware configuration only,
>>> you may keep a table of { chip-name, saturation ratio} in this
>>> driver and look up the saturation ratio based on the chip-name.
>>
>> OK, I'll add new property for saturation_ratio.
>>
>> I'll implement to use default saturation_ratio value ,
>> if dt node don't include saturation_ratio property.
> 
> Yes. I didn't talk with DT maintainers and I do not have much
> experience with DT; however, it appears that such values are not
> recommended to be in DTS files and this value is determined by
> the SoC model number without complications in the driver file.
> 

[PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

[Chanwoo Choi]

On 01/13/2015 06:07 PM, MyungJoo Ham wrote:
>>  
>> Dear Myungjoo,
>>
>> On 01/13/2015 05:42 PM, MyungJoo Ham wrote:
>>>>   
>>>>  This patch adds the generic exynos bus frequency driver for memory bus
>>>> with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
>>>> for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
>>>> support the memory bus frequency driver for Exynos SoCs.
>>>>
>>>> Each memory bus block has a clock for memory bus speed and frequency
>>>> table which is changed according to the utilization of memory bus on runtime.
>>>> And then each memory bus group has the one more memory bus blocks and
>>>> OPP table (including frequency and voltage), regulator, devfreq-event
>>>> devices.
>>>>
>>>> There are a little difference about the number of memory bus because each Exynos
>>>> SoC have the different sub-IP and different memory bus speed. In spite of this
>>>> difference among Exynos SoCs, we can support almost Exynos SoC by adding
>>>> unique data of memory bus to devicetree file.
>>>>
>>>> Cc: Myungjoo Ham <myungjoo.ham@samsung.com>
>>>> Cc: Kyungmin Park <kyungmin.park@samsung.com>
>>>> Cc: Kukjin Kim <kgene@kernel.org>
>>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>>>> ---
>>>>  drivers/devfreq/Kconfig          |  15 +
>>>>  drivers/devfreq/Makefile         |   1 +
>>>>  drivers/devfreq/exynos-busfreq.c | 589 +++++++++++++++++++++++++++++++++++++++
>>>>  3 files changed, 605 insertions(+)
>>>>  create mode 100644 drivers/devfreq/exynos-busfreq.c
>>>
>>> Exynos drivers are located at drivers/devfreq/exynos/
>>> Please relocate/rename exynos-busfreq.c
>>
>> OK. I'll move it at drivers/devfreq/exynos directory.
>> Do you prefer 'exynos-bus.c' instead of 'exynos-busfreq.c'?
>> If you reply, I'll change it.
> 
> exynos-bus looks more pretty :)

OK, I'll change the driver name according to your comment.

Best Regards,
Chanwoo Choi

> 
>>
>>>
>>> []
>>>
>>>> diff --git a/drivers/devfreq/exynos-busfreq.c b/drivers/devfreq/exynos-busfreq.c
>>>> new file mode 100644
>>>> index 0000000..b180f43
>>>> --- /dev/null
>>>> +++ b/drivers/devfreq/exynos-busfreq.c
>>>
>>> []
>>>
>>>> +
>>>> +#define BUS_SATURATION_RATIO	40
>>>
>>> In order to be a common driver, this should be tunable.
>>>
>>> Because .dts is supposed to have hardware configuration only,
>>> you may keep a table of { chip-name, saturation ratio} in this
>>> driver and look up the saturation ratio based on the chip-name.
>>
>> OK, I'll add new property for saturation_ratio.
>>
>> I'll implement to use default saturation_ratio value ,
>> if dt node don't include saturation_ratio property.
> 
> Yes. I didn't talk with DT maintainers and I do not have much
> experience with DT; however, it appears that such values are not
> recommended to be in DTS files and this value is determined by
> the SoC model number without complications in the driver file.
> 

[PATCHv3 0/8] devfreq: Add generic exynos memory-bus frequency driver

[Chanwoo Choi]

This patch-set adds the generic exynos bus frequency driver for memory bus
with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
support the memory bus frequency driver for Exynos SoCs.

Each memory bus block has a clock for memory bus speed and frequency
table which is changed according to the utilization of memory bus on runtime.
And then each memory bus group has the one more memory bus blocks and
OPP table (including frequency and voltage), regulator, devfreq-event
devices.

There are a little difference about the number of memory bus because each Exynos
SoC have the different sub-IP and different memory bus speed. In spite of this
difference among Exynos SoCs, we can support almost Exynos SoC by adding
unique data of memory bus to devicetree file.

Depend on:
- v3.19-rc3
- [PATCHv7 00/10] devfreq: Add devfreq-event class to provide raw data for devfreq device
  : https://lkml.org/lkml/2015/1/7/795

Changelog:

Changes from v2:
(https://lkml.org/lkml/2014/12/31/2)
- Support the memory bus frequency feature for Exynos3250-based Monk board
- Fix build warning about variable uninitialized

Changes from v1:
(https://lkml.org/lkml/2014/12/23/178)
- This patchset is rebased on v3.19-rc2.
- Fix bug after wake-up from suspend state. If devfreq device fail to get event,
  exynos-busfreq retry to set the event for starting.
- Add memory bus group of Exynos4x12/Exynos4210
- Add divider clock id for Exynos4 memory bus frequency
- Support memory bus frequency driver on Exynos4412-based TRATS2 board
- This patch-set has the dependency on following patch-set[1]:
  [1] [PATCHv6 0/9] devfreq: Add devfreq-event class to provide raw data for devfreq device
  : https://lkml.org/lkml/2014/12/28/139

Chanwoo Choi (8):
  devfreq: exynos: Add generic exynos memory bus frequency driver
  devfreq: exynos: Add documentation for generic exynos memory bus frequency driver
  ARM: dts: Add memory bus node for Exynos3250
  clk: samsung: exynos4: Add divider clock id for memory bus frequency
  ARM: dts: Add memory bus node for Exynos4x12
  ARM: dts: Add memory bus node for Exynos4210
  ARM: dts: Add memory bus node for Exynos3250-based Rinato/Monk board
  ARM: dts: Add memory bus node for Exynos4412-based TRATS2 board

 .../devicetree/bindings/devfreq/exynos-busfreq.txt | 184 +++++++
 arch/arm/boot/dts/exynos3250-monk.dts              |  12 +
 arch/arm/boot/dts/exynos3250-rinato.dts            |  12 +
 arch/arm/boot/dts/exynos3250.dtsi                  | 125 +++++
 arch/arm/boot/dts/exynos4210.dtsi                  |  93 ++++
 arch/arm/boot/dts/exynos4412-trats2.dts            |  12 +
 arch/arm/boot/dts/exynos4x12.dtsi                  | 121 +++++
 drivers/clk/samsung/clk-exynos4.c                  |  10 +-
 drivers/devfreq/Kconfig                            |  15 +
 drivers/devfreq/Makefile                           |   1 +
 drivers/devfreq/exynos-busfreq.c                   | 589 +++++++++++++++++++++
 include/dt-bindings/clock/exynos4.h                |   7 +-
 12 files changed, 1175 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/devfreq/exynos-busfreq.txt
 create mode 100644 drivers/devfreq/exynos-busfreq.c

-- 
1.8.5.5

[PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

[Chanwoo Choi]

This patch adds the generic exynos bus frequency driver for memory bus
with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
support the memory bus frequency driver for Exynos SoCs.

Each memory bus block has a clock for memory bus speed and frequency
table which is changed according to the utilization of memory bus on runtime.
And then each memory bus group has the one more memory bus blocks and
OPP table (including frequency and voltage), regulator, devfreq-event
devices.

There are a little difference about the number of memory bus because each Exynos
SoC have the different sub-IP and different memory bus speed. In spite of this
difference among Exynos SoCs, we can support almost Exynos SoC by adding
unique data of memory bus to devicetree file.

Cc: Myungjoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Kukjin Kim <kgene@kernel.org>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
---
 drivers/devfreq/Kconfig          |  15 +
 drivers/devfreq/Makefile         |   1 +
 drivers/devfreq/exynos-busfreq.c | 589 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 605 insertions(+)
 create mode 100644 drivers/devfreq/exynos-busfreq.c

diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
index 21f8f17..f1003eb 100644
--- a/drivers/devfreq/Kconfig
+++ b/drivers/devfreq/Kconfig
@@ -65,6 +65,21 @@ config DEVFREQ_GOV_USERSPACE
 
 comment "DEVFREQ Drivers"
 
+config ARM_EXYNOS_BUS_DEVFREQ
+	bool "EXYNOS Memory Bus DEVFREQ Driver"
+	depends on ARCH_EXYNOS
+	select DEVFREQ_GOV_SIMPLE_ONDEMAND
+	select DEVFREQ_EVENT_EXYNOS_PPMU
+	select PM_DEVFREQ_EVENT
+	select PM_OPP
+	help
+	  This adds the common DEVFREQ driver for Exynos Memory bus. Exynos
+	  Memory bus has one more group of memory bus (e.g, MIF and INT block).
+	  Each memory bus group could contain many memoby bus block. It reads
+	  PPMU counters of memory controllers by using DEVFREQ-event device
+	  and adjusts the operating frequencies and voltages with OPP support.
+	  This does not yet operate with optimal voltages.
+
 config ARM_EXYNOS4_BUS_DEVFREQ
 	bool "ARM Exynos4210/4212/4412 Memory Bus DEVFREQ Driver"
 	depends on (CPU_EXYNOS4210 || SOC_EXYNOS4212 || SOC_EXYNOS4412) && !ARCH_MULTIPLATFORM
diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
index c449336..2b82a4c 100644
--- a/drivers/devfreq/Makefile
+++ b/drivers/devfreq/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)	+= governor_powersave.o
 obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
 
 # DEVFREQ Drivers
+obj-$(CONFIG_ARCH_EXYNOS)		+= exynos-busfreq.o
 obj-$(CONFIG_ARM_EXYNOS4_BUS_DEVFREQ)	+= exynos/
 obj-$(CONFIG_ARM_EXYNOS5_BUS_DEVFREQ)	+= exynos/
 
diff --git a/drivers/devfreq/exynos-busfreq.c b/drivers/devfreq/exynos-busfreq.c
new file mode 100644
index 0000000..b180f43
--- /dev/null
+++ b/drivers/devfreq/exynos-busfreq.c
@@ -0,0 +1,589 @@
+/*
+ * Generic Exynos Memory Bus Frequency driver with DEVFREQ Framework
+ *
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ * Author : Chanwoo Choi <cw00.choi@samsung.com>
+ *
+ * This driver is based on exynos4_bus.c, which was written
+ * by MyungJoo Ham <myungjoo.ham@samsung.com>, Samsung Electronics.
+ *
+ * This driver support Exynos Memory Bus frequency feature by using in DEVFREQ
+ * framework. This version supprots Exynos3250/Exynos4 series/Exynos5260 SoC.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/devfreq.h>
+#include <linux/devfreq-event.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/pm_opp.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+#define BUS_SATURATION_RATIO	40
+#define SAFEVOLT		50000
+
+struct exynos_memory_bus_opp_info {
+	unsigned long rate;
+	unsigned long volt;
+};
+
+struct exynos_memory_bus_block {
+	struct clk *clk;
+	struct exynos_memory_bus_opp_info *freq_table;
+};
+
+struct exynos_memory_bus_data {
+	/* devfreq device to monitor and control memory bus group */
+	struct device *dev;
+	struct devfreq *devfreq;
+
+	struct exynos_memory_bus_opp_info *freq_table;
+	unsigned int freq_count;
+	struct regulator *regulator;
+	struct mutex lock;
+
+	struct exynos_memory_bus_opp_info curr_opp;
+
+	struct exynos_memory_bus_block *block;
+	unsigned int block_count;
+
+	/* devfreq-event device to get current state of memory bus group */
+	struct devfreq_event_dev **edev;
+	unsigned int edev_count;
+};
+
+/*
+ * Initialize the memory bus group/block by parsing dt node in the devicetree
+ */
+static int of_init_memory_bus(struct device_node *np,
+			      struct exynos_memory_bus_data *data)
+{
+	struct device *dev = data->dev;
+	struct dev_pm_opp *opp;
+	unsigned long rate, volt;
+	int i, ret, count, size;
+
+	/* Get the freq/voltage OPP table to scale memory bus frequency */
+	ret = of_init_opp_table(dev);
+	if (ret < 0) {
+		dev_err(dev, "failed to get OPP table\n");
+		return ret;
+	}
+
+	rcu_read_lock();
+
+	data->freq_count = dev_pm_opp_get_opp_count(dev);
+	if (data->freq_count <= 0) {
+		dev_err(dev, "failed to get the count of OPP entry\n");
+		rcu_read_unlock();
+		return -EINVAL;
+	}
+
+	size = sizeof(*data->freq_table) * data->freq_count;
+	data->freq_table = devm_kzalloc(dev, size, GFP_KERNEL);
+	if (!data->freq_table) {
+		rcu_read_unlock();
+		return -ENOMEM;
+	}
+
+	for (i = 0, rate = 0; i < data->freq_count; i++, rate++) {
+		opp = dev_pm_opp_find_freq_ceil(dev, &rate);
+		if (IS_ERR(opp)) {
+			dev_err(dev, "failed to find dev_pm_opp\n");
+			rcu_read_unlock();
+			return PTR_ERR(opp);
+		}
+
+		volt = dev_pm_opp_get_voltage(opp);
+
+		data->freq_table[i].rate = rate;
+		data->freq_table[i].volt = volt;
+
+		dev_dbg(dev, "Level%d : freq(%ld), voltage(%ld)\n", i, rate, volt);
+	}
+
+	rcu_read_unlock();
+
+	/* Get the regulator to provide memory bus group with the power */
+	data->regulator = devm_regulator_get(dev, "vdd-mem");
+	if (IS_ERR(data->regulator)) {
+		dev_err(dev, "failed to get vdd-memory regulator\n");
+		return PTR_ERR(data->regulator);
+	}
+
+	ret = regulator_enable(data->regulator);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable vdd-memory regulator\n");
+		return ret;
+	}
+
+	/*
+	 * Get the devfreq-event devices to get the current state of
+	 * memory bus group. This raw data will be used in devfreq governor.
+	 */
+	count = devfreq_event_get_edev_count(dev);
+	if (count < 0) {
+		dev_err(dev, "failed to get the count of devfreq-event dev\n");
+		return count;
+	}
+	data->edev_count = count;
+
+	size = sizeof(*data->edev) * count;
+	data->edev = devm_kzalloc(dev, size, GFP_KERNEL);
+	if (!data->edev)
+		return -ENOMEM;
+
+	for (i = 0; i < count; i++) {
+		data->edev[i] = devfreq_event_get_edev_by_phandle(dev, i);
+		if (IS_ERR(data->edev[i])) {
+			of_free_opp_table(dev);
+			return -EPROBE_DEFER;
+		}
+	}
+
+	return 0;
+}
+
+static int of_init_memory_bus_block(struct device_node *np,
+				    struct exynos_memory_bus_data *data)
+{
+	struct exynos_memory_bus_block *block;
+	struct device *dev = data->dev;
+	struct device_node *buses_np, *node;
+	int i, count;
+
+	buses_np = of_get_child_by_name(np, "blocks");
+	if (!buses_np) {
+		dev_err(dev,
+			"failed to get child node of memory bus\n");
+		return -EINVAL;
+	}
+
+	count = of_get_child_count(buses_np);
+	block = devm_kzalloc(dev, sizeof(*block) * count, GFP_KERNEL);
+	if (!block)
+		return -ENOMEM;
+	data->block = block;
+	data->block_count = count;
+
+	/* Parse the information of memory bus block */
+	i = 0;
+	for_each_child_of_node(buses_np, node) {
+		const struct property *prop;
+		const __be32 *val;
+		int j, nr, size;
+
+		block = &data->block[i++];
+
+		/* Get the frequency table of each memory bus block */
+		prop = of_find_property(node, "frequency", NULL);
+		if (!prop)
+			return -ENODEV;
+		if (!prop->value)
+			return -ENODATA;
+
+		nr = prop->length / sizeof(u32);
+		if (!nr)
+			return -EINVAL;
+
+		if (nr != data->freq_count) {
+			dev_err(dev, "the size of frequency table is different \
+					from OPP table\n");
+			return -EINVAL;
+		}
+
+		size = sizeof(*block->freq_table) * nr;
+		block->freq_table = devm_kzalloc(dev, size, GFP_KERNEL);
+		if (!block->freq_table)
+			return -ENOMEM;
+
+		val = prop->value;
+		for (j = nr - 1; j >= 0; j--)
+			block->freq_table[j].rate = be32_to_cpup(val++) * 1000;
+
+		for (j = 0; j < nr; j++)
+			dev_dbg(dev, "%s: Level%d : freq(%ld)\n",
+				node->name, j, block->freq_table[j].rate);
+
+		/* Get the clock of each memory bus block */
+		block->clk = of_clk_get_by_name(node, "memory-bus");
+		if (IS_ERR(block->clk)) {
+			dev_err(dev, "failed to get memory-bus clock in %s\n",
+					node->name);
+			return PTR_ERR(block->clk);
+		}
+		clk_prepare_enable(block->clk);
+
+		of_node_put(node);
+	}
+
+	of_node_put(buses_np);
+
+	return 0;
+}
+
+/*
+ * Control the devfreq-event device to get the current state of memory bus
+ */
+static int exynos_busfreq_enable_edev(struct exynos_memory_bus_data *data)
+{
+	int i, ret;
+
+	for (i = 0; i < data->edev_count; i++) {
+		ret = devfreq_event_enable_edev(data->edev[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int exynos_busfreq_disable_edev(struct exynos_memory_bus_data *data)
+{
+	int i, ret;
+
+	for (i = 0; i < data->edev_count; i++) {
+		ret = devfreq_event_disable_edev(data->edev[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+
+static int exynos_busfreq_set_event(struct exynos_memory_bus_data *data)
+{
+	int i, ret;
+
+	for (i = 0; i < data->edev_count; i++) {
+		ret = devfreq_event_set_event(data->edev[i],
+					DEVFREQ_EVENT_TYPE_RAW_DATA);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int exynos_busfreq_get_event(struct exynos_memory_bus_data *data,
+					struct devfreq_event_data *edata)
+{
+	struct devfreq_event_data event_data;
+	unsigned long event = 0, total_event = 0;
+	int i, ret = 0;
+
+	for (i = 0; i < data->edev_count; i++) {
+		ret = devfreq_event_get_event(data->edev[i],
+					DEVFREQ_EVENT_TYPE_RAW_DATA,
+					&event_data);
+		if (ret < 0)
+			return ret;
+
+		if (i == 0 || event_data.event > event) {
+			event = event_data.event;
+			total_event = event_data.total_event;
+		}
+	}
+
+	edata->event = event;
+	edata->total_event = total_event;
+
+	return ret;
+}
+
+/*
+ * Must necessary function for devfreq governor
+ */
+
+static int exynos_busfreq_set_frequency(struct exynos_memory_bus_data *data,
+				struct exynos_memory_bus_opp_info *new_opp)
+{
+	int i, j;
+
+	for (i = 0; i < data->freq_count; i++)
+		if (new_opp->rate == data->freq_table[i].rate)
+			break;
+
+	if (i == data->freq_count)
+		i = data->freq_count - 1;
+
+	for (j = 0; j < data->block_count; j++)
+		clk_set_rate(data->block[j].clk,
+				data->block[j].freq_table[i].rate);
+
+	return 0;
+}
+
+static int exynos_busfreq_target(struct device *dev, unsigned long *freq,
+				 u32 flags)
+{
+	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
+	struct exynos_memory_bus_opp_info new_opp;
+	unsigned long new_freq, old_freq;
+	struct dev_pm_opp *opp;
+	int ret = 0;
+
+	/* Get new opp-info instance according to new busfreq clock */
+	rcu_read_lock();
+	opp = devfreq_recommended_opp(dev, freq, flags);
+	if (IS_ERR_OR_NULL(opp)) {
+		dev_err(dev, "failed to get recommed opp instance\n");
+		rcu_read_unlock();
+		return PTR_ERR(opp);
+	}
+	new_opp.rate = dev_pm_opp_get_freq(opp);
+	new_opp.volt = dev_pm_opp_get_voltage(opp);
+	rcu_read_unlock();
+
+	old_freq = data->curr_opp.rate;
+	new_freq = new_opp.rate;
+	if (old_freq == new_freq)
+		return 0;
+
+	dev_dbg(dev, "Change the frequency of memory bus (%ld kHz -> %ld kHz)\n",
+			old_freq / 1000, new_freq / 1000);
+
+	/* Change voltage/clock according to new busfreq level */
+	mutex_lock(&data->lock);
+
+	if (old_freq < new_freq) {
+		ret = regulator_set_voltage(data->regulator, new_opp.volt,
+						new_opp.volt + SAFEVOLT);
+		if (ret < 0) {
+			dev_err(data->dev, "failed to set voltage\n");
+			regulator_set_voltage(data->regulator,
+					data->curr_opp.rate,
+					data->curr_opp.rate + SAFEVOLT);
+			goto out;
+		}
+	}
+
+	exynos_busfreq_set_frequency(data, &new_opp);
+	if (ret < 0) {
+		dev_err(dev, "failed to change clock of memory bus\n");
+		goto out;
+	}
+
+	if (old_freq > new_freq) {
+		ret = regulator_set_voltage(data->regulator, new_opp.volt,
+						new_opp.volt + SAFEVOLT);
+		if (ret < 0) {
+			dev_err(data->dev, "failed to set voltage\n");
+			regulator_set_voltage(data->regulator,
+					data->curr_opp.rate,
+					data->curr_opp.rate + SAFEVOLT);
+			goto out;
+		}
+	}
+
+	data->curr_opp = new_opp;
+
+out:
+	mutex_unlock(&data->lock);
+
+	return ret;
+}
+
+static int exynos_busfreq_get_dev_status(struct device *dev,
+					 struct devfreq_dev_status *stat)
+{
+	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
+	struct devfreq_event_data edata;
+	int ret;
+
+	stat->current_frequency = data->curr_opp.rate;
+
+	ret = exynos_busfreq_get_event(data, &edata);
+	if (ret < 0) {
+		stat->total_time = stat->busy_time = 0;
+		goto err;
+	}
+
+	stat->busy_time = (edata.event * 100) / BUS_SATURATION_RATIO;
+	stat->total_time = edata.total_event;
+
+	dev_dbg(dev, "Usage of devfreq-event : %ld/%ld\n", stat->busy_time,
+							stat->total_time);
+
+err:
+	ret = exynos_busfreq_set_event(data);
+	if (ret < 0) {
+		dev_err(dev, "failed to set event to devfreq-event devices\n");
+		return ret;
+	}
+
+	return ret;
+}
+
+static void exynos_busfreq_exit(struct device *dev)
+{
+	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
+	int i, ret;
+
+	ret = exynos_busfreq_disable_edev(data);
+	if (ret < 0)
+		dev_warn(dev, "failed to disable the devfreq-event devices\n");
+
+	for (i = 0; i < data->block_count; i++)
+		clk_disable_unprepare(data->block[i].clk);
+
+	if (regulator_is_enabled(data->regulator))
+		regulator_disable(data->regulator);
+
+	of_free_opp_table(dev);
+}
+
+static struct devfreq_dev_profile exynos_memory_bus_profile = {
+	.polling_ms	= 100,
+	.target		= exynos_busfreq_target,
+	.get_dev_status	= exynos_busfreq_get_dev_status,
+	.exit		= exynos_busfreq_exit,
+};
+
+static struct devfreq_simple_ondemand_data exynos_memory_bus_ondemand_data = {
+	.upthreshold		= 40,
+	.downdifferential	= 5,
+};
+
+static int exynos_busfreq_probe(struct platform_device *pdev)
+{
+	struct exynos_memory_bus_data *data;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	int ret;
+
+	if (!np) {
+		dev_err(dev, "failed to find devicetree node\n");
+		return -EINVAL;
+	}
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+	mutex_init(&data->lock);
+	data->dev = &pdev->dev;
+	platform_set_drvdata(pdev, data);
+
+	/* Initialize */
+	ret = of_init_memory_bus(np, data);
+	if (ret < 0) {
+		dev_err(dev, "failed to initialize memory-bus\n");
+		return ret;
+	}
+
+	ret = of_init_memory_bus_block(np, data);
+	if (ret < 0) {
+		dev_err(dev, "failed to initialize memory-bus block\n");
+		return ret;
+	}
+
+	/* Add devfreq device for DVFS of memory bus */
+	data->devfreq = devm_devfreq_add_device(dev,
+					&exynos_memory_bus_profile,
+					"simple_ondemand",
+					&exynos_memory_bus_ondemand_data);
+	if (IS_ERR_OR_NULL(data->devfreq)) {
+		dev_err(dev, "failed to add devfreq device\n");
+		return  PTR_ERR(data->devfreq);
+	}
+
+	/* Register opp_notifier to catch the change of OPP  */
+	ret = devm_devfreq_register_opp_notifier(dev, data->devfreq);
+	if (ret < 0) {
+		dev_err(dev, "failed to register opp notifier\n");
+		return ret;
+	}
+
+	/*
+	 * Enable devfreq-event to get raw data which is used to determine
+	 * current memory bus load.
+	 */
+	ret = exynos_busfreq_enable_edev(data);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable devfreq-event devices\n");
+		return ret;
+	}
+
+	ret = exynos_busfreq_set_event(data);
+	if (ret < 0) {
+		dev_err(dev, "failed to set event to devfreq-event devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int exynos_busfreq_remove(struct platform_device *pdev)
+{
+	/*
+	 * devfreq_dev_profile.exit() have to free the resource of this
+	 * device driver.
+	 */
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int exynos_busfreq_resume(struct device *dev)
+{
+	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = exynos_busfreq_enable_edev(data);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable the devfreq-event devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int exynos_busfreq_suspend(struct device *dev)
+{
+	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = exynos_busfreq_disable_edev(data);
+	if (ret < 0) {
+		dev_err(dev, "failed to disable the devfreq-event devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+#endif
+
+static const struct dev_pm_ops exynos_busfreq_pm = {
+	SET_SYSTEM_SLEEP_PM_OPS(exynos_busfreq_suspend, exynos_busfreq_resume)
+};
+
+static const struct of_device_id exynos_busfreq_of_match[] = {
+	{ .compatible = "samsung,exynos-memory-bus", },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, exynos_busfreq_of_match);
+
+static struct platform_driver exynos_busfreq_platdrv = {
+	.probe		= exynos_busfreq_probe,
+	.remove		= exynos_busfreq_remove,
+	.driver = {
+		.name	= "exynos-memory-bus",
+		.owner	= THIS_MODULE,
+		.pm	= &exynos_busfreq_pm,
+		.of_match_table = of_match_ptr(exynos_busfreq_of_match),
+	},
+};
+module_platform_driver(exynos_busfreq_platdrv);
+
+MODULE_DESCRIPTION("Generic Exynos Memory Bus Frequency driver");
+MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
+MODULE_LICENSE("GPL v2");
-- 
1.8.5.5

[PATCHv3 1/8] devfreq: exynos: Add generic exynos memory bus frequency driver

[Chanwoo Choi]

This patch adds the generic exynos bus frequency driver for memory bus
with DEVFREQ framework. The Samsung Exynos SoCs have the common architecture
for memory bus between DRAM memory and MMC/sub IP in SoC. This driver can
support the memory bus frequency driver for Exynos SoCs.

Each memory bus block has a clock for memory bus speed and frequency
table which is changed according to the utilization of memory bus on runtime.
And then each memory bus group has the one more memory bus blocks and
OPP table (including frequency and voltage), regulator, devfreq-event
devices.

There are a little difference about the number of memory bus because each Exynos
SoC have the different sub-IP and different memory bus speed. In spite of this
difference among Exynos SoCs, we can support almost Exynos SoC by adding
unique data of memory bus to devicetree file.

Cc: Myungjoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Kukjin Kim <kgene@kernel.org>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
---
 drivers/devfreq/Kconfig          |  15 +
 drivers/devfreq/Makefile         |   1 +
 drivers/devfreq/exynos-busfreq.c | 589 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 605 insertions(+)
 create mode 100644 drivers/devfreq/exynos-busfreq.c

diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
index 21f8f17..f1003eb 100644
--- a/drivers/devfreq/Kconfig
+++ b/drivers/devfreq/Kconfig
@@ -65,6 +65,21 @@ config DEVFREQ_GOV_USERSPACE
 
 comment "DEVFREQ Drivers"
 
+config ARM_EXYNOS_BUS_DEVFREQ
+	bool "EXYNOS Memory Bus DEVFREQ Driver"
+	depends on ARCH_EXYNOS
+	select DEVFREQ_GOV_SIMPLE_ONDEMAND
+	select DEVFREQ_EVENT_EXYNOS_PPMU
+	select PM_DEVFREQ_EVENT
+	select PM_OPP
+	help
+	  This adds the common DEVFREQ driver for Exynos Memory bus. Exynos
+	  Memory bus has one more group of memory bus (e.g, MIF and INT block).
+	  Each memory bus group could contain many memoby bus block. It reads
+	  PPMU counters of memory controllers by using DEVFREQ-event device
+	  and adjusts the operating frequencies and voltages with OPP support.
+	  This does not yet operate with optimal voltages.
+
 config ARM_EXYNOS4_BUS_DEVFREQ
 	bool "ARM Exynos4210/4212/4412 Memory Bus DEVFREQ Driver"
 	depends on (CPU_EXYNOS4210 || SOC_EXYNOS4212 || SOC_EXYNOS4412) && !ARCH_MULTIPLATFORM
diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
index c449336..2b82a4c 100644
--- a/drivers/devfreq/Makefile
+++ b/drivers/devfreq/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)	+= governor_powersave.o
 obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
 
 # DEVFREQ Drivers
+obj-$(CONFIG_ARCH_EXYNOS)		+= exynos-busfreq.o
 obj-$(CONFIG_ARM_EXYNOS4_BUS_DEVFREQ)	+= exynos/
 obj-$(CONFIG_ARM_EXYNOS5_BUS_DEVFREQ)	+= exynos/
 
diff --git a/drivers/devfreq/exynos-busfreq.c b/drivers/devfreq/exynos-busfreq.c
new file mode 100644
index 0000000..b180f43
--- /dev/null
+++ b/drivers/devfreq/exynos-busfreq.c
@@ -0,0 +1,589 @@
+/*
+ * Generic Exynos Memory Bus Frequency driver with DEVFREQ Framework
+ *
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ * Author : Chanwoo Choi <cw00.choi@samsung.com>
+ *
+ * This driver is based on exynos4_bus.c, which was written
+ * by MyungJoo Ham <myungjoo.ham@samsung.com>, Samsung Electronics.
+ *
+ * This driver support Exynos Memory Bus frequency feature by using in DEVFREQ
+ * framework. This version supprots Exynos3250/Exynos4 series/Exynos5260 SoC.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/devfreq.h>
+#include <linux/devfreq-event.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/pm_opp.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+#define BUS_SATURATION_RATIO	40
+#define SAFEVOLT		50000
+
+struct exynos_memory_bus_opp_info {
+	unsigned long rate;
+	unsigned long volt;
+};
+
+struct exynos_memory_bus_block {
+	struct clk *clk;
+	struct exynos_memory_bus_opp_info *freq_table;
+};
+
+struct exynos_memory_bus_data {
+	/* devfreq device to monitor and control memory bus group */
+	struct device *dev;
+	struct devfreq *devfreq;
+
+	struct exynos_memory_bus_opp_info *freq_table;
+	unsigned int freq_count;
+	struct regulator *regulator;
+	struct mutex lock;
+
+	struct exynos_memory_bus_opp_info curr_opp;
+
+	struct exynos_memory_bus_block *block;
+	unsigned int block_count;
+
+	/* devfreq-event device to get current state of memory bus group */
+	struct devfreq_event_dev **edev;
+	unsigned int edev_count;
+};
+
+/*
+ * Initialize the memory bus group/block by parsing dt node in the devicetree
+ */
+static int of_init_memory_bus(struct device_node *np,
+			      struct exynos_memory_bus_data *data)
+{
+	struct device *dev = data->dev;
+	struct dev_pm_opp *opp;
+	unsigned long rate, volt;
+	int i, ret, count, size;
+
+	/* Get the freq/voltage OPP table to scale memory bus frequency */
+	ret = of_init_opp_table(dev);
+	if (ret < 0) {
+		dev_err(dev, "failed to get OPP table\n");
+		return ret;
+	}
+
+	rcu_read_lock();
+
+	data->freq_count = dev_pm_opp_get_opp_count(dev);
+	if (data->freq_count <= 0) {
+		dev_err(dev, "failed to get the count of OPP entry\n");
+		rcu_read_unlock();
+		return -EINVAL;
+	}
+
+	size = sizeof(*data->freq_table) * data->freq_count;
+	data->freq_table = devm_kzalloc(dev, size, GFP_KERNEL);
+	if (!data->freq_table) {
+		rcu_read_unlock();
+		return -ENOMEM;
+	}
+
+	for (i = 0, rate = 0; i < data->freq_count; i++, rate++) {
+		opp = dev_pm_opp_find_freq_ceil(dev, &rate);
+		if (IS_ERR(opp)) {
+			dev_err(dev, "failed to find dev_pm_opp\n");
+			rcu_read_unlock();
+			return PTR_ERR(opp);
+		}
+
+		volt = dev_pm_opp_get_voltage(opp);
+
+		data->freq_table[i].rate = rate;
+		data->freq_table[i].volt = volt;
+
+		dev_dbg(dev, "Level%d : freq(%ld), voltage(%ld)\n", i, rate, volt);
+	}
+
+	rcu_read_unlock();
+
+	/* Get the regulator to provide memory bus group with the power */
+	data->regulator = devm_regulator_get(dev, "vdd-mem");
+	if (IS_ERR(data->regulator)) {
+		dev_err(dev, "failed to get vdd-memory regulator\n");
+		return PTR_ERR(data->regulator);
+	}
+
+	ret = regulator_enable(data->regulator);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable vdd-memory regulator\n");
+		return ret;
+	}
+
+	/*
+	 * Get the devfreq-event devices to get the current state of
+	 * memory bus group. This raw data will be used in devfreq governor.
+	 */
+	count = devfreq_event_get_edev_count(dev);
+	if (count < 0) {
+		dev_err(dev, "failed to get the count of devfreq-event dev\n");
+		return count;
+	}
+	data->edev_count = count;
+
+	size = sizeof(*data->edev) * count;
+	data->edev = devm_kzalloc(dev, size, GFP_KERNEL);
+	if (!data->edev)
+		return -ENOMEM;
+
+	for (i = 0; i < count; i++) {
+		data->edev[i] = devfreq_event_get_edev_by_phandle(dev, i);
+		if (IS_ERR(data->edev[i])) {
+			of_free_opp_table(dev);
+			return -EPROBE_DEFER;
+		}
+	}
+
+	return 0;
+}
+
+static int of_init_memory_bus_block(struct device_node *np,
+				    struct exynos_memory_bus_data *data)
+{
+	struct exynos_memory_bus_block *block;
+	struct device *dev = data->dev;
+	struct device_node *buses_np, *node;
+	int i, count;
+
+	buses_np = of_get_child_by_name(np, "blocks");
+	if (!buses_np) {
+		dev_err(dev,
+			"failed to get child node of memory bus\n");
+		return -EINVAL;
+	}
+
+	count = of_get_child_count(buses_np);
+	block = devm_kzalloc(dev, sizeof(*block) * count, GFP_KERNEL);
+	if (!block)
+		return -ENOMEM;
+	data->block = block;
+	data->block_count = count;
+
+	/* Parse the information of memory bus block */
+	i = 0;
+	for_each_child_of_node(buses_np, node) {
+		const struct property *prop;
+		const __be32 *val;
+		int j, nr, size;
+
+		block = &data->block[i++];
+
+		/* Get the frequency table of each memory bus block */
+		prop = of_find_property(node, "frequency", NULL);
+		if (!prop)
+			return -ENODEV;
+		if (!prop->value)
+			return -ENODATA;
+
+		nr = prop->length / sizeof(u32);
+		if (!nr)
+			return -EINVAL;
+
+		if (nr != data->freq_count) {
+			dev_err(dev, "the size of frequency table is different \
+					from OPP table\n");
+			return -EINVAL;
+		}
+
+		size = sizeof(*block->freq_table) * nr;
+		block->freq_table = devm_kzalloc(dev, size, GFP_KERNEL);
+		if (!block->freq_table)
+			return -ENOMEM;
+
+		val = prop->value;
+		for (j = nr - 1; j >= 0; j--)
+			block->freq_table[j].rate = be32_to_cpup(val++) * 1000;
+
+		for (j = 0; j < nr; j++)
+			dev_dbg(dev, "%s: Level%d : freq(%ld)\n",
+				node->name, j, block->freq_table[j].rate);
+
+		/* Get the clock of each memory bus block */
+		block->clk = of_clk_get_by_name(node, "memory-bus");
+		if (IS_ERR(block->clk)) {
+			dev_err(dev, "failed to get memory-bus clock in %s\n",
+					node->name);
+			return PTR_ERR(block->clk);
+		}
+		clk_prepare_enable(block->clk);
+
+		of_node_put(node);
+	}
+
+	of_node_put(buses_np);
+
+	return 0;
+}
+
+/*
+ * Control the devfreq-event device to get the current state of memory bus
+ */
+static int exynos_busfreq_enable_edev(struct exynos_memory_bus_data *data)
+{
+	int i, ret;
+
+	for (i = 0; i < data->edev_count; i++) {
+		ret = devfreq_event_enable_edev(data->edev[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int exynos_busfreq_disable_edev(struct exynos_memory_bus_data *data)
+{
+	int i, ret;
+
+	for (i = 0; i < data->edev_count; i++) {
+		ret = devfreq_event_disable_edev(data->edev[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+
+static int exynos_busfreq_set_event(struct exynos_memory_bus_data *data)
+{
+	int i, ret;
+
+	for (i = 0; i < data->edev_count; i++) {
+		ret = devfreq_event_set_event(data->edev[i],
+					DEVFREQ_EVENT_TYPE_RAW_DATA);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int exynos_busfreq_get_event(struct exynos_memory_bus_data *data,
+					struct devfreq_event_data *edata)
+{
+	struct devfreq_event_data event_data;
+	unsigned long event = 0, total_event = 0;
+	int i, ret = 0;
+
+	for (i = 0; i < data->edev_count; i++) {
+		ret = devfreq_event_get_event(data->edev[i],
+					DEVFREQ_EVENT_TYPE_RAW_DATA,
+					&event_data);
+		if (ret < 0)
+			return ret;
+
+		if (i == 0 || event_data.event > event) {
+			event = event_data.event;
+			total_event = event_data.total_event;
+		}
+	}
+
+	edata->event = event;
+	edata->total_event = total_event;
+
+	return ret;
+}
+
+/*
+ * Must necessary function for devfreq governor
+ */
+
+static int exynos_busfreq_set_frequency(struct exynos_memory_bus_data *data,
+				struct exynos_memory_bus_opp_info *new_opp)
+{
+	int i, j;
+
+	for (i = 0; i < data->freq_count; i++)
+		if (new_opp->rate == data->freq_table[i].rate)
+			break;
+
+	if (i == data->freq_count)
+		i = data->freq_count - 1;
+
+	for (j = 0; j < data->block_count; j++)
+		clk_set_rate(data->block[j].clk,
+				data->block[j].freq_table[i].rate);
+
+	return 0;
+}
+
+static int exynos_busfreq_target(struct device *dev, unsigned long *freq,
+				 u32 flags)
+{
+	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
+	struct exynos_memory_bus_opp_info new_opp;
+	unsigned long new_freq, old_freq;
+	struct dev_pm_opp *opp;
+	int ret = 0;
+
+	/* Get new opp-info instance according to new busfreq clock */
+	rcu_read_lock();
+	opp = devfreq_recommended_opp(dev, freq, flags);
+	if (IS_ERR_OR_NULL(opp)) {
+		dev_err(dev, "failed to get recommed opp instance\n");
+		rcu_read_unlock();
+		return PTR_ERR(opp);
+	}
+	new_opp.rate = dev_pm_opp_get_freq(opp);
+	new_opp.volt = dev_pm_opp_get_voltage(opp);
+	rcu_read_unlock();
+
+	old_freq = data->curr_opp.rate;
+	new_freq = new_opp.rate;
+	if (old_freq == new_freq)
+		return 0;
+
+	dev_dbg(dev, "Change the frequency of memory bus (%ld kHz -> %ld kHz)\n",
+			old_freq / 1000, new_freq / 1000);
+
+	/* Change voltage/clock according to new busfreq level */
+	mutex_lock(&data->lock);
+
+	if (old_freq < new_freq) {
+		ret = regulator_set_voltage(data->regulator, new_opp.volt,
+						new_opp.volt + SAFEVOLT);
+		if (ret < 0) {
+			dev_err(data->dev, "failed to set voltage\n");
+			regulator_set_voltage(data->regulator,
+					data->curr_opp.rate,
+					data->curr_opp.rate + SAFEVOLT);
+			goto out;
+		}
+	}
+
+	exynos_busfreq_set_frequency(data, &new_opp);
+	if (ret < 0) {
+		dev_err(dev, "failed to change clock of memory bus\n");
+		goto out;
+	}
+
+	if (old_freq > new_freq) {
+		ret = regulator_set_voltage(data->regulator, new_opp.volt,
+						new_opp.volt + SAFEVOLT);
+		if (ret < 0) {
+			dev_err(data->dev, "failed to set voltage\n");
+			regulator_set_voltage(data->regulator,
+					data->curr_opp.rate,
+					data->curr_opp.rate + SAFEVOLT);
+			goto out;
+		}
+	}
+
+	data->curr_opp = new_opp;
+
+out:
+	mutex_unlock(&data->lock);
+
+	return ret;
+}
+
+static int exynos_busfreq_get_dev_status(struct device *dev,
+					 struct devfreq_dev_status *stat)
+{
+	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
+	struct devfreq_event_data edata;
+	int ret;
+
+	stat->current_frequency = data->curr_opp.rate;
+
+	ret = exynos_busfreq_get_event(data, &edata);
+	if (ret < 0) {
+		stat->total_time = stat->busy_time = 0;
+		goto err;
+	}
+
+	stat->busy_time = (edata.event * 100) / BUS_SATURATION_RATIO;
+	stat->total_time = edata.total_event;
+
+	dev_dbg(dev, "Usage of devfreq-event : %ld/%ld\n", stat->busy_time,
+							stat->total_time);
+
+err:
+	ret = exynos_busfreq_set_event(data);
+	if (ret < 0) {
+		dev_err(dev, "failed to set event to devfreq-event devices\n");
+		return ret;
+	}
+
+	return ret;
+}
+
+static void exynos_busfreq_exit(struct device *dev)
+{
+	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
+	int i, ret;
+
+	ret = exynos_busfreq_disable_edev(data);
+	if (ret < 0)
+		dev_warn(dev, "failed to disable the devfreq-event devices\n");
+
+	for (i = 0; i < data->block_count; i++)
+		clk_disable_unprepare(data->block[i].clk);
+
+	if (regulator_is_enabled(data->regulator))
+		regulator_disable(data->regulator);
+
+	of_free_opp_table(dev);
+}
+
+static struct devfreq_dev_profile exynos_memory_bus_profile = {
+	.polling_ms	= 100,
+	.target		= exynos_busfreq_target,
+	.get_dev_status	= exynos_busfreq_get_dev_status,
+	.exit		= exynos_busfreq_exit,
+};
+
+static struct devfreq_simple_ondemand_data exynos_memory_bus_ondemand_data = {
+	.upthreshold		= 40,
+	.downdifferential	= 5,
+};
+
+static int exynos_busfreq_probe(struct platform_device *pdev)
+{
+	struct exynos_memory_bus_data *data;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	int ret;
+
+	if (!np) {
+		dev_err(dev, "failed to find devicetree node\n");
+		return -EINVAL;
+	}
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+	mutex_init(&data->lock);
+	data->dev = &pdev->dev;
+	platform_set_drvdata(pdev, data);
+
+	/* Initialize */
+	ret = of_init_memory_bus(np, data);
+	if (ret < 0) {
+		dev_err(dev, "failed to initialize memory-bus\n");
+		return ret;
+	}
+
+	ret = of_init_memory_bus_block(np, data);
+	if (ret < 0) {
+		dev_err(dev, "failed to initialize memory-bus block\n");
+		return ret;
+	}
+
+	/* Add devfreq device for DVFS of memory bus */
+	data->devfreq = devm_devfreq_add_device(dev,
+					&exynos_memory_bus_profile,
+					"simple_ondemand",
+					&exynos_memory_bus_ondemand_data);
+	if (IS_ERR_OR_NULL(data->devfreq)) {
+		dev_err(dev, "failed to add devfreq device\n");
+		return  PTR_ERR(data->devfreq);
+	}
+
+	/* Register opp_notifier to catch the change of OPP  */
+	ret = devm_devfreq_register_opp_notifier(dev, data->devfreq);
+	if (ret < 0) {
+		dev_err(dev, "failed to register opp notifier\n");
+		return ret;
+	}
+
+	/*
+	 * Enable devfreq-event to get raw data which is used to determine
+	 * current memory bus load.
+	 */
+	ret = exynos_busfreq_enable_edev(data);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable devfreq-event devices\n");
+		return ret;
+	}
+
+	ret = exynos_busfreq_set_event(data);
+	if (ret < 0) {
+		dev_err(dev, "failed to set event to devfreq-event devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int exynos_busfreq_remove(struct platform_device *pdev)
+{
+	/*
+	 * devfreq_dev_profile.exit() have to free the resource of this
+	 * device driver.
+	 */
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int exynos_busfreq_resume(struct device *dev)
+{
+	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = exynos_busfreq_enable_edev(data);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable the devfreq-event devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int exynos_busfreq_suspend(struct device *dev)
+{
+	struct exynos_memory_bus_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = exynos_busfreq_disable_edev(data);
+	if (ret < 0) {
+		dev_err(dev, "failed to disable the devfreq-event devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+#endif
+
+static const struct dev_pm_ops exynos_busfreq_pm = {
+	SET_SYSTEM_SLEEP_PM_OPS(exynos_busfreq_suspend, exynos_busfreq_resume)
+};
+
+static const struct of_device_id exynos_busfreq_of_match[] = {
+	{ .compatible = "samsung,exynos-memory-bus", },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, exynos_busfreq_of_match);
+
+static struct platform_driver exynos_busfreq_platdrv = {
+	.probe		= exynos_busfreq_probe,
+	.remove		= exynos_busfreq_remove,
+	.driver = {
+		.name	= "exynos-memory-bus",
+		.owner	= THIS_MODULE,
+		.pm	= &exynos_busfreq_pm,
+		.of_match_table = of_match_ptr(exynos_busfreq_of_match),
+	},
+};
+module_platform_driver(exynos_busfreq_platdrv);
+
+MODULE_DESCRIPTION("Generic Exynos Memory Bus Frequency driver");
+MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
+MODULE_LICENSE("GPL v2");
-- 
1.8.5.5