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Message-ID: <6450334d-596b-4982-8a17-eefc8585e036@wanadoo.fr>
Date: Mon, 8 Apr 2024 22:26:16 +0200
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From: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Subject: Re: [PATCH v1 3/4] usb: dwc3: exynos: Use
 devm_regulator_bulk_get_enable() helper function
To: Anand Moon <linux.amoon@gmail.com>
Cc: Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
 Alim Akhtar <alim.akhtar@samsung.com>, linux-usb@vger.kernel.org,
 linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org,
 linux-kernel@vger.kernel.org
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Le 08/04/2024 à 12:02, Anand Moon a écrit :
> Hi Christophe,
> 
> On Fri, 5 Apr 2024 at 21:42, Christophe JAILLET
> <christophe.jaillet@wanadoo.fr> wrote:
>>
>> Le 05/04/2024 à 08:10, Anand Moon a écrit :
>>>    Hi Christophe, Krzysztof,
>>>
>>> On Mon, 4 Mar 2024 at 17:16, Anand Moon <linux.amoon@gmail.com> wrote:
>>>>
>>>> Hi Christophe,
>>>>
>>>> On Sun, 3 Mar 2024 at 00:07, Christophe JAILLET
>>>> <christophe.jaillet@wanadoo.fr> wrote:
>>>>>
>>>>> Le 02/03/2024 à 17:48, Anand Moon a écrit :
>>>>>> Hi Christophe,
>>>>>>
>>>>>> On Sat, 2 Mar 2024 at 21:20, Christophe JAILLET
>>>>>> <christophe.jaillet@wanadoo.fr> wrote:
>>>>>>>
>>>>>>> Le 01/03/2024 à 20:38, Anand Moon a écrit :
>>>>>>>> Use devm_regulator_bulk_get_enable() instead of open coded
>>>>>>>> 'devm_regulator_get(), regulator_enable(), regulator_disable().
>>>>>>>>
>>>>>>>> Signed-off-by: Anand Moon <linux.amoon@gmail.com>
>>>>>>>> ---
>>>>>>>>      drivers/usb/dwc3/dwc3-exynos.c | 49 +++-------------------------------
>>>>>>>>      1 file changed, 4 insertions(+), 45 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/usb/dwc3/dwc3-exynos.c b/drivers/usb/dwc3/dwc3-exynos.c
>>>>>>>> index 5d365ca51771..7c77f3c69825 100644
>>>>>>>> --- a/drivers/usb/dwc3/dwc3-exynos.c
>>>>>>>> +++ b/drivers/usb/dwc3/dwc3-exynos.c
>>>>>>>> @@ -32,9 +32,6 @@ struct dwc3_exynos {
>>>>>>>>          struct clk              *clks[DWC3_EXYNOS_MAX_CLOCKS];
>>>>>>>>          int                     num_clks;
>>>>>>>>          int                     suspend_clk_idx;
>>>>>>>> -
>>>>>>>> -     struct regulator        *vdd33;
>>>>>>>> -     struct regulator        *vdd10;
>>>>>>>>      };
>>>>>>>>
>>>>>>>>      static int dwc3_exynos_probe(struct platform_device *pdev)
>>>>>>>> @@ -44,6 +41,7 @@ static int dwc3_exynos_probe(struct platform_device *pdev)
>>>>>>>>          struct device_node      *node = dev->of_node;
>>>>>>>>          const struct dwc3_exynos_driverdata *driver_data;
>>>>>>>>          int                     i, ret;
>>>>>>>> +     static const char * const regulators[] = { "vdd33", "vdd10" };
>>>>>>>>
>>>>>>>>          exynos = devm_kzalloc(dev, sizeof(*exynos), GFP_KERNEL);
>>>>>>>>          if (!exynos)
>>>>>>>> @@ -78,27 +76,9 @@ static int dwc3_exynos_probe(struct platform_device *pdev)
>>>>>>>>          if (exynos->suspend_clk_idx >= 0)
>>>>>>>>                  clk_prepare_enable(exynos->clks[exynos->suspend_clk_idx]);
>>>>>>>>
>>>>>>>> -     exynos->vdd33 = devm_regulator_get(dev, "vdd33");
>>>>>>>> -     if (IS_ERR(exynos->vdd33)) {
>>>>>>>> -             ret = PTR_ERR(exynos->vdd33);
>>>>>>>> -             goto vdd33_err;
>>>>>>>> -     }
>>>>>>>> -     ret = regulator_enable(exynos->vdd33);
>>>>>>>> -     if (ret) {
>>>>>>>> -             dev_err(dev, "Failed to enable VDD33 supply\n");
>>>>>>>> -             goto vdd33_err;
>>>>>>>> -     }
>>>>>>>> -
>>>>>>>> -     exynos->vdd10 = devm_regulator_get(dev, "vdd10");
>>>>>>>> -     if (IS_ERR(exynos->vdd10)) {
>>>>>>>> -             ret = PTR_ERR(exynos->vdd10);
>>>>>>>> -             goto vdd10_err;
>>>>>>>> -     }
>>>>>>>> -     ret = regulator_enable(exynos->vdd10);
>>>>>>>> -     if (ret) {
>>>>>>>> -             dev_err(dev, "Failed to enable VDD10 supply\n");
>>>>>>>> -             goto vdd10_err;
>>>>>>>> -     }
>>>>>>>> +     ret = devm_regulator_bulk_get_enable(dev, ARRAY_SIZE(regulators), regulators);
>>>>>>>> +     if (ret)
>>>>>>>> +             return dev_err_probe(dev, ret, "Failed to enable regulators\n");
>>>>>>>>
>>>>>>>>          if (node) {
>>>>>>>>                  ret = of_platform_populate(node, NULL, NULL, dev);
>>>>>>>> @@ -115,10 +95,6 @@ static int dwc3_exynos_probe(struct platform_device *pdev)
>>>>>>>>          return 0;
>>>>>>>>
>>>>>>>>      populate_err:
>>>>>>>> -     regulator_disable(exynos->vdd10);
>>>>>>>> -vdd10_err:
>>>>>>>> -     regulator_disable(exynos->vdd33);
>>>>>>>> -vdd33_err:
>>>>>>>>          for (i = exynos->num_clks - 1; i >= 0; i--)
>>>>>>>>                  clk_disable_unprepare(exynos->clks[i]);
>>>>>>>>
>>>>>>>> @@ -140,9 +116,6 @@ static void dwc3_exynos_remove(struct platform_device *pdev)
>>>>>>>>
>>>>>>>>          if (exynos->suspend_clk_idx >= 0)
>>>>>>>>                  clk_disable_unprepare(exynos->clks[exynos->suspend_clk_idx]);
>>>>>>>> -
>>>>>>>> -     regulator_disable(exynos->vdd33);
>>>>>>>> -     regulator_disable(exynos->vdd10);
>>>>>>>>      }
>>>>>>>>
>>>>>>>>      static const struct dwc3_exynos_driverdata exynos5250_drvdata = {
>>>>>>>> @@ -196,9 +169,6 @@ static int dwc3_exynos_suspend(struct device *dev)
>>>>>>>>          for (i = exynos->num_clks - 1; i >= 0; i--)
>>>>>>>>                  clk_disable_unprepare(exynos->clks[i]);
>>>>>>>>
>>>>>>>> -     regulator_disable(exynos->vdd33);
>>>>>>>> -     regulator_disable(exynos->vdd10);
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Same here, I don't think that removing regulator_[en|dis]able from the
>>>>>>> suspend and resume function is correct.
>>>>>>>
>>>>>>> The goal is to stop some hardware when the system is suspended, in order
>>>>>>> to save some power.
>>>>>> Ok,
>>>>>>>
>>>>>>> Why did you removed it?
>>>>>>
>>>>>> As per the description of the function  devm_regulator_bulk_get_enable
>>>>>>
>>>>>> * This helper function allows drivers to get several regulator
>>>>>>     * consumers in one operation with management, the regulators will
>>>>>>     * automatically be freed when the device is unbound.  If any of the
>>>>>>     * regulators cannot be acquired then any regulators that were
>>>>>>     * allocated will be freed before returning to the caller.
>>>>>
>>>>> The code in suspend/resume is not about freeing some resources. It is
>>>>> about enabling/disabling some hardware to save some power.
>>>>>
>>>>> Think to the probe/remove functions as the software in the kernel that
>>>>> knows how to handle some hardawre, and the suspend/resume as the on/off
>>>>> button to power-on and off the electrical chips.
>>>>>
>>>>> When the system is suspended, the software is still around. But some
>>>>> hardware can be set in a low consumption mode to save some power.
>>>>>
>>>>> IMHO, part of the code you removed changed this behaviour and increase
>>>>> the power consumption when the system is suspended.
>>>>>
>>>>
>>>> You are correct, I have changed the regulator API from
>>>> devm_regulator_get_enable to devm_regulator_bulk_get_enable
>>>> which changes this behavior.
>>>> I will fix it in the next version.
>>>>
>>>>> CJ
>>>
>>> I could not find any example in the kernel to support
>>> devm_regulator_bulk_disable
>>> but here is my modified file.
>>>
>>> If you have any suggestions for this plz let me know.
>>
>> I don't think that your approach is correct, and I don't think that the
>> proposed patch does what you expect it to do.
>>
>> Calling a devm_ function in suspend/resume functions looks really
>> strange to me and is likely broken.
>>
>> Especially here, devm_regulator_bulk_get_enable() in the resume function
>> allocates some memory that is not freed in
>> devm_regulator_bulk_disable(), because the API is not designed to work
>> like that. So this could generate a kind of memory leak.
>>
>>
>> *I think that the code is good enough as-is*, but if you really want to
>> change something, maybe:
>>      - devm_regulator_get()+regulator_enable() in the probe could be
>> changed to devm_regulator_get_enable()
>>      - the resume/suspend function should be left as-is with
>> regulator_disable()/regulator_ensable()
>>      - remove regulator_disable() from the error handling path of the
>> probe and from the remove function.
>>
>> I *think* it would work.
>>
> No devm_regulator_get_enable use the same logic as
> devm_regulator_bulk_get_enable
> to enable the regulator.

Yes, the logic is the same, but you get a pointer to the "struct 
regulator" which can be used to disable/enable in the suspend/resume 
functions.

With the bulk version, you can not do that.

See my first reply on your 3/4 patch.

> 
> [0] https://elixir.bootlin.com/linux/latest/source/drivers/regulator/devres.c#L126
> 
> So as of now I am dropping the changes on the regulator in this patch series.

I do agree that it is certainly the way to go here.

CJ

> 
>> CJ
>>
> Thanks for your inputs.
> 
> Thanks
> 
> -Anand
> 
>