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

[Anand Moon]

Hi Christophe,

On Fri, 5 Apr 2024 at 21:42, Christophe JAILLET
<christophe.jaillet@xxxxxxxxxx> 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@xxxxxxxxx> wrote:
> >>
> >> Hi Christophe,
> >>
> >> On Sun, 3 Mar 2024 at 00:07, Christophe JAILLET
> >> <christophe.jaillet@xxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxx>
> >>>>>> ---
> >>>>>>     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.

[0] https://elixir.bootlin.com/linux/latest/source/drivers/regulator/devresc#L126

So as of now I am dropping the changes on the regulator in this patch series.

> CJ
>
Thanks for your inputs.

Thanks

-Anand