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

From: Christophe JAILLET
Date: Fri Apr 05 2024 - 12:14:12 EST

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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.

CJ

-----8<----------8<----------
diff --git a/drivers/usb/dwc3/dwc3-exynos.c b/drivers/usb/dwc3/dwc3-exynos.c
index 6d07592ad022..2f808cb9a006 100644
--- a/drivers/usb/dwc3/dwc3-exynos.c
+++ b/drivers/usb/dwc3/dwc3-exynos.c
@@ -34,6 +34,8 @@ struct dwc3_exynos {
int suspend_clk_idx;
};

+static const char * const regulators[] = { "vdd33", "vdd10" };
+
static int dwc3_exynos_probe(struct platform_device *pdev)
{
struct dwc3_exynos *exynos;
@@ -41,7 +43,6 @@ 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)
@@ -166,6 +167,8 @@ static int __maybe_unused
dwc3_exynos_suspend(struct device *dev)
struct dwc3_exynos *exynos = dev_get_drvdata(dev);
int i;

+ devm_regulator_bulk_disable(dev);
+
for (i = exynos->num_clks - 1; i >= 0; i--)
clk_disable_unprepare(exynos->clks[i]);

@@ -177,6 +180,11 @@ static int __maybe_unused
dwc3_exynos_resume(struct device *dev)
struct dwc3_exynos *exynos = dev_get_drvdata(dev);
int i, ret;

+ ret = devm_regulator_bulk_get_enable(dev, ARRAY_SIZE(regulators),
+ regulators);
+ if (ret)
+ dev_err(dev, "Failed to enable regulators\n");
+
for (i = 0; i < exynos->num_clks; i++) {
ret = clk_prepare_enable(exynos->clks[i]);
if (ret) {

To support these changes we need to export the
devm_regulator_bulk_disable function.
-----8<----------8<----------
diff --git a/drivers/regulator/devres.c b/drivers/regulator/devres.c
index 90bb0d178885..97eed739f929 100644
--- a/drivers/regulator/devres.c
+++ b/drivers/regulator/devres.c
@@ -318,7 +318,7 @@ void devm_regulator_bulk_put(struct
regulator_bulk_data *consumers)
}
EXPORT_SYMBOL_GPL(devm_regulator_bulk_put);

-static void devm_regulator_bulk_disable(void *res)
+void devm_regulator_bulk_disable(void *res)
{
struct regulator_bulk_devres *devres = res;
int i;
@@ -326,6 +326,7 @@ static void devm_regulator_bulk_disable(void *res)
for (i = 0; i < devres->num_consumers; i++)
regulator_disable(devres->consumers[i].consumer);
}
+EXPORT_SYMBOL_GPL(devm_regulator_bulk_disable);

/**
* devm_regulator_bulk_get_enable - managed get'n enable multiple regulators
diff --git a/include/linux/regulator/consumer.h
b/include/linux/regulator/consumer.h
index 4660582a3302..ce7d28306b17 100644
--- a/include/linux/regulator/consumer.h
+++ b/include/linux/regulator/consumer.h
@@ -214,6 +214,7 @@ int __must_check regulator_bulk_enable(int num_consumers,
struct regulator_bulk_data *consumers);
int devm_regulator_bulk_get_enable(struct device *dev, int num_consumers,
const char * const *id);
+void devm_regulator_bulk_disable(void *res);
int regulator_bulk_disable(int num_consumers,
struct regulator_bulk_data *consumers);
int regulator_bulk_force_disable(int num_consumers,
--------------------------------------------------------------------------

Thanks
-Anand

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In reply to: Anand Moon: "Re: [PATCH v1 3/4] usb: dwc3: exynos: Use devm_regulator_bulk_get_enable() helper function"
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