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Message-ID: <6450334d-596b-4982-8a17-eefc8585e036@wanadoo.fr>
Date: Mon, 8 Apr 2024 22:26:16 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Anand Moon <linux.amoon@...il.com>
Cc: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
Alim Akhtar <alim.akhtar@...sung.com>, linux-usb@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/4] usb: dwc3: exynos: Use
devm_regulator_bulk_get_enable() helper function
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@...adoo.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@...il.com> wrote:
>>>>
>>>> Hi Christophe,
>>>>
>>>> On Sun, 3 Mar 2024 at 00:07, Christophe JAILLET
>>>> <christophe.jaillet@...adoo.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@...adoo.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@...il.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
>
>
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