Re: [PATCH] usb: xhci-mvebu: use regulator_set_enable_if_allowed()

On 8/21/26 10:50 AM, Bruno Banelli wrote:
> On Fri, Aug 21, 2026 at 4:25 AM Marek Vasut <[email protected]> wrote:
>>
>> On 8/20/26 5:10 PM, Bruno Banelli wrote:
>>> Since commit 4fcba5d556b4 ("regulator: implement basic reference
>>> counter") regulator_set_enable() returns -EALREADY when a fixed or
>>> GPIO regulator has already been enabled. On boards whose VBUS
>>> regulator carries regulator-always-on or regulator-boot-on -
>>> armada-8040-mcbin.dts is one - regulator_autoset() enables it during
>>> the regulator's own probe, so the subsequent enable in xhci_usb_probe()
>>> fails and the controller is never registered:
>>>
>>>     starting USB...
>>>     Failed to turn ON the VBUS regulator
>>>     Bus usb3@500000: probe failed, error -114
>>>     No USB controllers found
>>>
>>> Use regulator_set_enable_if_allowed(), which tolerates -EALREADY, in
>>> the same way as commit 0830333c4743 ("usb: ehci-generic: Use
>>> regulator_set_enable_if_allowed") and the other drivers converted
>>> after the reference counter was introduced.
>>>
>>> Tested on a SolidRun MACCHIATObin (Armada 8040), where USB mass
>>> storage now enumerates.
>>>
>>> Fixes: 4fcba5d556b4 ("regulator: implement basic reference counter")
>>> Signed-off-by: Bruno Banelli <[email protected]>
>>> ---
>>>    drivers/usb/host/xhci-mvebu.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/usb/host/xhci-mvebu.c b/drivers/usb/host/xhci-mvebu.c
>>> index c294a56b3c..53b3e82b66 100644
>>> --- a/drivers/usb/host/xhci-mvebu.c
>>> +++ b/drivers/usb/host/xhci-mvebu.c
>>> @@ -51,7 +51,7 @@ static int xhci_usb_probe(struct udevice *dev)
>>>
>>>        ret = device_get_supply_regulator(dev, "vbus-supply", &regulator);
>>>        if (!ret) {
>>> -             ret = regulator_set_enable(regulator, true);
>>> +             ret = regulator_set_enable_if_allowed(regulator, true);
>>>                if (ret) {
>>>                        printf("Failed to turn ON the VBUS regulator\n");
>> Do you need to handle -ENOSYS return value here ?
> 
> No - regulator_set_enable_if_allowed() already absorbs it, which is the
> reason for using it rather than open-coding the check in the driver:
> 
>    int regulator_set_enable_if_allowed(struct udevice *dev, bool enable)
>    {
>            int ret;
> 
>            ret = regulator_set_enable(dev, enable);
>            if (ret == -ENOSYS || ret == -EACCES)
>                    return 0;
See include/power/regulator.h if DM_REGULATOR is not enabled condition:

593 static inline int regulator_set_enable_if_allowed(struct udevice 
*dev, bool enable)
594 {
595         return -ENOSYS;
596 }