Re: [PATCH v1 3/4] usb: dwc3: exynos: Use devm_regulator_bulk_get_enable() helper function

[Christophe JAILLET <christophe.jaillet@wanadoo.fr>]

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.

CJ

> 
> [0] https://elixir.bootlin.com/linux/latest/source/drivers/regulator/devres.c#L330
> 
> I have tested with rtc suspend resume and did not find any issue with
> this.patch.
> 
>>
>> CJ
>>
> Thanks
> -Anand
> 
>