Re: [PATCH v2 2/4] devfreq: exynos-bus: convert to use dev_pm_opp_set_rate()

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

Hi,

On 19. 7. 16. 오후 7:59, Bartlomiej Zolnierkiewicz wrote:
> 
> On 7/16/19 12:33 PM, Chanwoo Choi wrote:
>> Hi Bartlomiej,
>>
>> On 19. 7. 16. 오후 7:13, Bartlomiej Zolnierkiewicz wrote:
>>>
>>> Hi Chanwoo,
>>>
>>> On 7/16/19 5:56 AM, Chanwoo Choi wrote:
>>>> Hi Kamil,
>>>>
>>>> Looks good to me. But, this patch has some issue.
>>>> I added the detailed reviews.
>>>>
>>>> I recommend that you make the separate patches as following
>>>> in order to clarify the role of which apply the dev_pm_opp_* function.
>>>>
>>>> First patch,
>>>> Need to consolidate the following two function into one function.
>>>> because the original exynos-bus.c has the problem that the regulator
>>>> of parent devfreq device have to be enabled before enabling the clock.
>>>> This issue did not happen because bootloader enables the bus-related
>>>> regulators before kernel booting.
>>>> - exynos_bus_parse_of()
>>>> - exynos_bus_parent_parse_of()
>>>>> Second patch,
>>>> Apply dev_pm_opp_set_regulators() and dev_pm_opp_set_rate()
>>>>
>>>>
>>>> On 19. 7. 15. 오후 9:04, Kamil Konieczny wrote:
>>>>> Reuse opp core code for setting bus clock and voltage. As a side
>>>>> effect this allow useage of coupled regulators feature (required
>>>>> for boards using Exynos5422/5800 SoCs) because dev_pm_opp_set_rate()
>>>>> uses regulator_set_voltage_triplet() for setting regulator voltage
>>>>> while the old code used regulator_set_voltage_tol() with fixed
>>>>> tolerance. This patch also removes no longer needed parsing of DT
>>>>> property "exynos,voltage-tolerance" (no Exynos devfreq DT node uses
>>>>> it).
>>>>>
>>>>> Signed-off-by: Kamil Konieczny <k.konieczny@partner.samsung.com>
>>>>> ---
>>>>>  drivers/devfreq/exynos-bus.c | 172 ++++++++++++++---------------------
>>>>>  1 file changed, 66 insertions(+), 106 deletions(-)
>>>>>
>>>>> diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
>>>>> index 486cc5b422f1..7fc4f76bd848 100644
>>>>> --- a/drivers/devfreq/exynos-bus.c
>>>>> +++ b/drivers/devfreq/exynos-bus.c
>>>>> @@ -25,7 +25,6 @@
>>>>>  #include <linux/slab.h>
>>>>>  
>>>>>  #define DEFAULT_SATURATION_RATIO	40
>>>>> -#define DEFAULT_VOLTAGE_TOLERANCE	2
>>>>>  
>>>>>  struct exynos_bus {
>>>>>  	struct device *dev;
>>>>> @@ -37,9 +36,9 @@ struct exynos_bus {
>>>>>  
>>>>>  	unsigned long curr_freq;
>>>>>  
>>>>> -	struct regulator *regulator;
>>>>> +	struct opp_table *opp_table;
>>>>> +
>>>>>  	struct clk *clk;
>>>>> -	unsigned int voltage_tolerance;
>>>>>  	unsigned int ratio;
>>>>>  };
>>>>>  
>>>>> @@ -99,56 +98,25 @@ static int exynos_bus_target(struct device *dev, unsigned long *freq, u32 flags)
>>>>>  {
>>>>>  	struct exynos_bus *bus = dev_get_drvdata(dev);
>>>>>  	struct dev_pm_opp *new_opp;
>>>>> -	unsigned long old_freq, new_freq, new_volt, tol;
>>>>>  	int ret = 0;
>>>>> -
>>>>> -	/* Get new opp-bus instance according to new bus clock */
>>>>> +	/*
>>>>> +	 * New frequency for bus may not be exactly matched to opp, adjust
>>>>> +	 * *freq to correct value.
>>>>> +	 */
>>>>
>>>> You better to change this comment with following styles
>>>> to keep the consistency:
>>>>
>>>> 	/* Get correct frequency for bus ... */
>>>>
>>>>>  	new_opp = devfreq_recommended_opp(dev, freq, flags);
>>>>>  	if (IS_ERR(new_opp)) {
>>>>>  		dev_err(dev, "failed to get recommended opp instance\n");
>>>>>  		return PTR_ERR(new_opp);
>>>>>  	}
>>>>>  
>>>>> -	new_freq = dev_pm_opp_get_freq(new_opp);
>>>>> -	new_volt = dev_pm_opp_get_voltage(new_opp);
>>>>>  	dev_pm_opp_put(new_opp);
>>>>>  
>>>>> -	old_freq = bus->curr_freq;
>>>>> -
>>>>> -	if (old_freq == new_freq)
>>>>> -		return 0;
>>>>> -	tol = new_volt * bus->voltage_tolerance / 100;
>>>>> -
>>>>>  	/* Change voltage and frequency according to new OPP level */
>>>>>  	mutex_lock(&bus->lock);
>>>>> +	ret = dev_pm_opp_set_rate(dev, *freq);
>>>>> +	if (!ret)
>>>>> +		bus->curr_freq = *freq;
>>>>
>>>> Have to print the error log if ret has minus error value.
>>>
>>> dev_pm_opp_set_rate() should print the error message on all
>>> errors so wouldn't printing the error log also here be superfluous?
>>>
>>> [ Please also note that the other user of dev_pm_opp_set_rate()
>>>   (cpufreq-dt cpufreq driver) doesn't do this. ]
>>
>> OK. Thanks for the explanation. 
>>
>>>
>>>> Modify it as following:
>>>>
>>>> 	if (ret < 0) {
>>>> 		dev_err(dev, "failed to set bus rate\n");
>>>> 		goto err:
>>>> 	}
>>>> 	bus->curr_freq = *freq;
>>>>
>>>> err:
>>>> 	mutex_unlock(&bus->lock);
>>>> 	
>>>> 	return ret;
>>>>
>>>>>  
>>>>> -	if (old_freq < new_freq) {
>>>>> -		ret = regulator_set_voltage_tol(bus->regulator, new_volt, tol);
>>>>> -		if (ret < 0) {
>>>>> -			dev_err(bus->dev, "failed to set voltage\n");
>>>>> -			goto out;
>>>>> -		}
>>>>> -	}
>>>>> -
>>>>> -	ret = clk_set_rate(bus->clk, new_freq);
>>>>> -	if (ret < 0) {
>>>>> -		dev_err(dev, "failed to change clock of bus\n");
>>>>> -		clk_set_rate(bus->clk, old_freq);
>>>>> -		goto out;
>>>>> -	}
>>>>> -
>>>>> -	if (old_freq > new_freq) {
>>>>> -		ret = regulator_set_voltage_tol(bus->regulator, new_volt, tol);
>>>>> -		if (ret < 0) {
>>>>> -			dev_err(bus->dev, "failed to set voltage\n");
>>>>> -			goto out;
>>>>> -		}
>>>>> -	}
>>>>> -	bus->curr_freq = new_freq;
>>>>> -
>>>>> -	dev_dbg(dev, "Set the frequency of bus (%luHz -> %luHz, %luHz)\n",
>>>>> -			old_freq, new_freq, clk_get_rate(bus->clk));
>>>>> -out:
>>>>>  	mutex_unlock(&bus->lock);
>>>>>  
>>>>>  	return ret;
>>>>> @@ -194,10 +162,11 @@ static void exynos_bus_exit(struct device *dev)
>>>>>  	if (ret < 0)
>>>>>  		dev_warn(dev, "failed to disable the devfreq-event devices\n");
>>>>>  
>>>>> -	if (bus->regulator)
>>>>> -		regulator_disable(bus->regulator);
>>>>> +	if (bus->opp_table)
>>>>> +		dev_pm_opp_put_regulators(bus->opp_table);
>>>>
>>>> Have to disable regulator after disabling the clock
>>>> to prevent the h/w fault.
>>>>
>>>> I think that you should call them with following sequence:
>>>>
>>>> 	clk_disable_unprepare(bus->clk);
>>>> 	if (bus->opp_table)
>>>> 		dev_pm_opp_put_regulators(bus->opp_table);
>>>> 	dev_pm_opp_of_remove_table(dev);
>>>>
>>>>>  
>>>>>  	dev_pm_opp_of_remove_table(dev);
>>>>> +
>>>>>  	clk_disable_unprepare(bus->clk);
>>>>>  }
>>>>>  
>>>>> @@ -209,39 +178,26 @@ static int exynos_bus_passive_target(struct device *dev, unsigned long *freq,
>>>>>  {
>>>>>  	struct exynos_bus *bus = dev_get_drvdata(dev);
>>>>>  	struct dev_pm_opp *new_opp;
>>>>> -	unsigned long old_freq, new_freq;
>>>>> -	int ret = 0;
>>>>> +	int ret;
>>>>>  
>>>>> -	/* Get new opp-bus instance according to new bus clock */
>>>>> +	/*
>>>>> +	 * New frequency for bus may not be exactly matched to opp, adjust
>>>>> +	 * *freq to correct value.
>>>>> +	 */
>>>>
>>>> You better to change this comment with following styles
>>>> to keep the consistency:
>>>>
>>>> 	/* Get correct frequency for bus ... */
>>>>
>>>>>  	new_opp = devfreq_recommended_opp(dev, freq, flags);
>>>>>  	if (IS_ERR(new_opp)) {
>>>>>  		dev_err(dev, "failed to get recommended opp instance\n");
>>>>>  		return PTR_ERR(new_opp);
>>>>>  	}
>>>>>  
>>>>> -	new_freq = dev_pm_opp_get_freq(new_opp);
>>>>>  	dev_pm_opp_put(new_opp);
>>>>>  
>>>>> -	old_freq = bus->curr_freq;
>>>>> -
>>>>> -	if (old_freq == new_freq)
>>>>> -		return 0;
>>>>> -
>>>>>  	/* Change the frequency according to new OPP level */
>>>>>  	mutex_lock(&bus->lock);
>>>>> +	ret = dev_pm_opp_set_rate(dev, *freq);
>>>>> +	if (!ret)
>>>>> +		bus->curr_freq = *freq;
>>>>
>>>> ditto. Have to print the error log, check above comment.
>>>>
>>>>>  
>>>>> -	ret = clk_set_rate(bus->clk, new_freq);
>>>>> -	if (ret < 0) {
>>>>> -		dev_err(dev, "failed to set the clock of bus\n");
>>>>> -		goto out;
>>>>> -	}
>>>>> -
>>>>> -	*freq = new_freq;
>>>>> -	bus->curr_freq = new_freq;
>>>>> -
>>>>> -	dev_dbg(dev, "Set the frequency of bus (%luHz -> %luHz, %luHz)\n",
>>>>> -			old_freq, new_freq, clk_get_rate(bus->clk));
>>>>> -out:
>>>>>  	mutex_unlock(&bus->lock);
>>>>>  
>>>>>  	return ret;
>>>>> @@ -259,20 +215,7 @@ static int exynos_bus_parent_parse_of(struct device_node *np,
>>>>>  					struct exynos_bus *bus)
>>>>>  {
>>>>>  	struct device *dev = bus->dev;
>>>>> -	int i, ret, count, size;
>>>>> -
>>>>> -	/* Get the regulator to provide each bus with the power */
>>>>> -	bus->regulator = devm_regulator_get(dev, "vdd");
>>>>> -	if (IS_ERR(bus->regulator)) {
>>>>> -		dev_err(dev, "failed to get VDD regulator\n");
>>>>> -		return PTR_ERR(bus->regulator);
>>>>> -	}
>>>>> -
>>>>> -	ret = regulator_enable(bus->regulator);
>>>>> -	if (ret < 0) {
>>>>> -		dev_err(dev, "failed to enable VDD regulator\n");
>>>>> -		return ret;
>>>>> -	}
>>>>> +	int i, count, size;
>>>>>  
>>>>>  	/*
>>>>>  	 * Get the devfreq-event devices to get the current utilization of
>>>>> @@ -281,24 +224,20 @@ static int exynos_bus_parent_parse_of(struct device_node *np,
>>>>>  	count = devfreq_event_get_edev_count(dev);
>>>>>  	if (count < 0) {
>>>>>  		dev_err(dev, "failed to get the count of devfreq-event dev\n");
>>>>> -		ret = count;
>>>>> -		goto err_regulator;
>>>>> +		return count;
>>>>>  	}
>>>>> +
>>>>>  	bus->edev_count = count;
>>>>>  
>>>>>  	size = sizeof(*bus->edev) * count;
>>>>>  	bus->edev = devm_kzalloc(dev, size, GFP_KERNEL);
>>>>> -	if (!bus->edev) {
>>>>> -		ret = -ENOMEM;
>>>>> -		goto err_regulator;
>>>>> -	}
>>>>> +	if (!bus->edev)
>>>>> +		return -ENOMEM;
>>>>>  
>>>>>  	for (i = 0; i < count; i++) {
>>>>>  		bus->edev[i] = devfreq_event_get_edev_by_phandle(dev, i);
>>>>> -		if (IS_ERR(bus->edev[i])) {
>>>>> -			ret = -EPROBE_DEFER;
>>>>> -			goto err_regulator;
>>>>> -		}
>>>>> +		if (IS_ERR(bus->edev[i]))
>>>>> +			return -EPROBE_DEFER;
>>>>>  	}
>>>>>  
>>>>>  	/*
>>>>> @@ -314,22 +253,15 @@ static int exynos_bus_parent_parse_of(struct device_node *np,
>>>>>  	if (of_property_read_u32(np, "exynos,saturation-ratio", &bus->ratio))
>>>>>  		bus->ratio = DEFAULT_SATURATION_RATIO;
>>>>>  
>>>>> -	if (of_property_read_u32(np, "exynos,voltage-tolerance",
>>>>> -					&bus->voltage_tolerance))
>>>>> -		bus->voltage_tolerance = DEFAULT_VOLTAGE_TOLERANCE;
>>>>> -
>>>>>  	return 0;
>>>>> -
>>>>> -err_regulator:
>>>>> -	regulator_disable(bus->regulator);
>>>>> -
>>>>> -	return ret;
>>>>>  }
>>>>>  
>>>>>  static int exynos_bus_parse_of(struct device_node *np,
>>>>> -			      struct exynos_bus *bus)
>>>>> +			      struct exynos_bus *bus, bool passive)
>>>>>  {
>>>>>  	struct device *dev = bus->dev;
>>>>> +	struct opp_table *opp_table;
>>>>> +	const char *vdd = "vdd";
>>>>>  	struct dev_pm_opp *opp;
>>>>>  	unsigned long rate;
>>>>>  	int ret;
>>>>> @@ -347,11 +279,22 @@ static int exynos_bus_parse_of(struct device_node *np,
>>>>>  		return ret;
>>>>>  	}
>>>>>  
>>>>> +	if (!passive) {
>>>>> +		opp_table = dev_pm_opp_set_regulators(dev, &vdd, 1);
>>>>> +		if (IS_ERR(opp_table)) {
>>>>> +			ret = PTR_ERR(opp_table);
>>>>> +			dev_err(dev, "failed to set regulators %d\n", ret);
>>>>> +			goto err_clk;/
>>>>> +		}
>>>>> +
>>>>> +		bus->opp_table = opp_table;
>>>>> +	}
>>>>
>>>> This driver has exynos_bus_parent_parse_of() function for parent devfreq device.
>>>> dev_pm_opp_set_regulators() have to be called in exynos_bus_parent_parse_of()
>>>> because the regulator is only used by parent devfreq device.
>>>
>>> exynos_bus_parse_of() is called for all devfreq devices (including
>>> parent) and (as you've noticed) the regulator should be enabled before
>>> enabling clock (which is done in exynos_bus_parse_of()) so adding
>>> extra argument to exynos_bus_parse_of() (like it is done currently in
>>> the patch) 
>>
>> I think that this patch has still the problem about call sequence
>> between clock and regulator as following:
> 
> Yes, this should be fixed (though the wrong sequence between regulator
> and clock handling is not introduced by the patchset itself and is present
> in the original driver code).
> 
>> 273         ret = clk_prepare_enable(bus->clk);                                     
>> 274         if (ret < 0) {                                                          
>> 275                 dev_err(dev, "failed to get enable clock\n");                   
>> 276                 return ret;                                                     
>> 277         }                                                                       
>> 278                                                                                 
>> 279         if (!passive) {                                                         
>> 280                 opp_table = dev_pm_opp_set_regulators(dev, &vdd, 1);            
>> 281                 if (IS_ERR(opp_table)) {                                        
>> 282                         ret = PTR_ERR(opp_table);                               
>> 283                         dev_err(dev, "failed to set regulators %d\n", ret);     
>> 284                         goto err_clk;                                           
>> 285                 }                                                               
>> 286                                                                                 
>> 287                 bus->opp_table = opp_table;                                     
>> 288         }                   
>>
>> makes it possible to do the setup correctly without the need
>>> of merging both functions into one huge function (which would be more
>>> difficult to follow than two simpler functions IMHO). Is that approach
>>> acceptable or do you prefer one big function?
>>
>> Actually, I don't force to make one function for both
>> exynos_bus_parse_of() and exynos_bus_parent_parse_of().
>>
>> If we just keep this code, dev_pm_opp_set_regulators()
>> should be handled in exynos_bus_parent_parse_of()
>> because only parent devfreq device controls the regulator.
> 
> Could your please explain rationale for this requirement (besides
> function name)?

OK. I hope to satisfy the following requirements:

1. Fix the sequence problem between clock and regulator for enabling them.
2. dev_pm_opp_set_regulator() have to be handled in exynos_bus_parent_parse_of()
   instead of exynos_bus_parse_of() for only parent devfreq device.
3. exynos_bus_parse_of() have to handle the only common properties
   of both parent devfreq device and passive devfreq device.

> 
> The patch adds 'bool passive' argument (which is set to false for
> parent devfreq device and true for child devfreq device) to
> exynos_bus_parse_of() (which is called for *all* devfreq devices

As I menteiond, exynos_bus_parse_of have to handle the only common
properties of both parent device and passive device. 

I gathered the properties for parent device into exynos_bus_parent_parse_of()
This way using 'bool passive' argument is not proper in exynos_bus_parse_of().


> and is called before exynos_bus_parent_parse_of()) and there is
> no hard requirement to call dev_pm_opp_set_regulators() in
> exynos_bus_parent_parse_of() so after only changing the ordering
> between regulator and clock handling the setup code should be
> correct.
> 
> [ Please note that this patch moves parent/child detection before
>   exynos_bus_parse_of() call. ]
> 
>> In order to keep the two functions, maybe have to change
>> the call the sequence between exynos_bus_parse_of() and
>> exynos_bus_parent_parse_of().
> 
> Doesn't seem to be needed, care to explain it more?

In order to fix the sequence problem between clock and regulator
with dev_pm_opp_set_regualtor() and want to keep two functions
(exynos_bus_parent_parse_of() and exynos_bus_parse_of()),
have to change the call order as following and then modify
the exception handling code when error happen.

	node = of_parse_phandle(dev->of_node, "devfreq", 0);                    
	if (node) {                                                             
		of_node_put(node);                                              
		passive = true
	}

	if (!passive)	
		exynos_bus_parent_parse_of()
			dev_pm_opp_set_regulator

	exynos_bus_parse_of()

> 
>> Once again, I don't force any fixed method. I want to fix them
>> with correct way.
>>
>>>
>>>>> +
>>>>>  	/* Get the freq and voltage from OPP table to scale the bus freq */
>>>>>  	ret = dev_pm_opp_of_add_table(dev);
>>>>>  	if (ret < 0) {
>>>>>  		dev_err(dev, "failed to get OPP table\n");
>>>>> -		goto err_clk;
>>>>> +		goto err_regulator;
>>>>>  	}
>>>>>  
>>>>>  	rate = clk_get_rate(bus->clk);
>>>>> @@ -362,6 +305,7 @@ static int exynos_bus_parse_of(struct device_node *np,
>>>>>  		ret = PTR_ERR(opp);
>>>>>  		goto err_opp;
>>>>>  	}
>>>>> +
>>>>>  	bus->curr_freq = dev_pm_opp_get_freq(opp);
>>>>>  	dev_pm_opp_put(opp);
>>>>>  
>>>>> @@ -369,6 +313,13 @@ static int exynos_bus_parse_of(struct device_node *np,
>>>>>  
>>>>>  err_opp:
>>>>>  	dev_pm_opp_of_remove_table(dev);
>>>>> +
>>>>> +err_regulator:
>>>>> +	if (bus->opp_table) {
>>>>> +		dev_pm_opp_put_regulators(bus->opp_table);
>>>>> +		bus->opp_table = NULL;
>>>>> +	}
>>>>
>>>> As I mentioned above, it it wrong to call dev_pm_opp_put_regulators()
>>>> after removing the opp_table by dev_pm_opp_of_remove_table().
>>>>
>>>>> +
>>>>>  err_clk:
>>>>>  	clk_disable_unprepare(bus->clk);
>>>>>  
>>>>> @@ -386,6 +337,7 @@ static int exynos_bus_probe(struct platform_device *pdev)
>>>>>  	struct exynos_bus *bus;
>>>>>  	int ret, max_state;
>>>>>  	unsigned long min_freq, max_freq;
>>>>> +	bool passive = false;
>>>>>  
>>>>>  	if (!np) {
>>>>>  		dev_err(dev, "failed to find devicetree node\n");
>>>>> @@ -395,12 +347,18 @@ static int exynos_bus_probe(struct platform_device *pdev)
>>>>>  	bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
>>>>>  	if (!bus)
>>>>>  		return -ENOMEM;
>>>>> +
>>>>>  	mutex_init(&bus->lock);
>>>>>  	bus->dev = &pdev->dev;
>>>>>  	platform_set_drvdata(pdev, bus);
>>>>> +	node = of_parse_phandle(dev->of_node, "devfreq", 0);
>>>>> +	if (node) {
>>>>> +		of_node_put(node);
>>>>> +		passive = true;
>>>>> +	}
>>>>>  
>>>>>  	/* Parse the device-tree to get the resource information */
>>>>> -	ret = exynos_bus_parse_of(np, bus);
>>>>> +	ret = exynos_bus_parse_of(np, bus, passive);
>>>>>  	if (ret < 0)
>>>>>  		return ret;
>>>>>  
>>>>> @@ -410,13 +368,10 @@ static int exynos_bus_probe(struct platform_device *pdev)
>>>>>  		goto err;
>>>>>  	}
>>>>>  
>>>>> -	node = of_parse_phandle(dev->of_node, "devfreq", 0);
>>>>> -	if (node) {
>>>>> -		of_node_put(node);
>>>>> +	if (passive)
>>>>>  		goto passive;
>>>>> -	} else {
>>>>> -		ret = exynos_bus_parent_parse_of(np, bus);
>>>>> -	}
>>>>> +
>>>>> +	ret = exynos_bus_parent_parse_of(np, bus);
>>>>>  
>>>>
>>>> Remove unneeded blank line.
>>>>
>>>>>  	if (ret < 0)
>>>>>  		goto err;
>>>>> @@ -509,6 +464,11 @@ static int exynos_bus_probe(struct platform_device *pdev)
>>>>>  
>>>>>  err:
>>>>>  	dev_pm_opp_of_remove_table(dev);
>>>>> +	if (bus->opp_table) {
>>>>> +		dev_pm_opp_put_regulators(bus->opp_table);
>>>>> +		bus->opp_table = NULL;
>>>>> +	}
>>>>> +
>>>>
>>>> ditto.
>>>> Have to disable regulator after disabling the clock
>>>> to prevent the h/w fault.
>>>>
>>>> I think that you should call them with following sequence:
>>>>
>>>> 	clk_disable_unprepare(bus->clk);
>>>> 	if (bus->opp_table)
>>>> 		dev_pm_opp_put_regulators(bus->opp_table);
>>>> 	dev_pm_opp_of_remove_table(dev);
>>>>
>>>>>  	clk_disable_unprepare(bus->clk);
>>>>>  
>>>>>  	return ret;
>>>
>>> Best regards,
>>> --
>>> Bartlomiej Zolnierkiewicz
>>> Samsung R&D Institute Poland
>>> Samsung Electronics
> 
> Best regards,
> --
> Bartlomiej Zolnierkiewicz
> Samsung R&D Institute Poland
> Samsung Electronics
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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