[PATCH] common: usb-hub: Reset hub port before scanning

[Marek Vasut]

On 12/3/23 22:42, Shantur Rathore wrote:
> Hi Marek,
> 
> On Sun, Dec 3, 2023 at 8:42 PM Marek Vasut <marex at denx.de> wrote:
>>
>> On 11/24/23 01:37, Shantur Rathore wrote:
>>> Hi Marek,
>>
>> Hi,
>>
>> sorry for the late reply.
>>
>>>>>>> In my case RockPro64, the power to usb ports onboard is controlled by
>>>>>>> a regulator.
>>>>>>> This regulator is enabled as part of init  as here
>>>>>>> https://github.com/u-boot/u-boot/blob/master/arch/arm/dts/rk3399-rockpro64.dtsi#L177
>>>>>>>
>>>>>>> On init, the usb devices connected to the port are powered up, in my
>>>>>>> case AM8180 (a RTL9210 based ) NVMe to USB enclosure with UAS.
>>>>>>> But the usb controller is only enabled at 'usb start' and by this time
>>>>>>> the device is in some state that it doesn't get detected.
>>>>>>>
>>>>>>> One way to make sure the devices connected to the ports are in an
>>>>>>> initialising state is by issuing a port reset before scanning the
>>>>>>> port.
>>>>>>
>>>>>> Why not remove this regulator-always-on and let the PHY driver turn the
>>>>>> VBUS ON only when it is needed ?
>>>>>>
>>>>>> Wouldn't that solve the problem too AND remove unnecessarily enabled
>>>>>> regulator ?
>>>>>>
>>>>>> [...]
>>>>>
>>>>> Removing the regulator-always-on does make it work but there are few issues
>>>>>
>>>>> 1. regulator is used to control power to multiple ports ( USB3.0 and
>>>>> USB2.0 in RockPro64 ),
>>>>> so this could lead to all ports turning off if a phy resets / turns off power
>>>>
>>>> I vaguely recall seeing some refcounting patch for regulator subsystem,
>>>> would that help ?
>>>
>>> I don't think this would be a problem for u-boot, but linux maybe.
>>
>> How so ?
> 
> Actually, I am wrong. I wasn't sure if there is refcounting for the
> regulator subsystem
> in linux. just found it has so this is null and void.
> 
>>
>>>>> 2. Even with regulator-always-on and without this reset port patch,
>>>>> linux was always
>>>>> able to detect the drive on the port, so there is something missing in u-boot.
>>>>> 3. Looking at usb hub code in Linux, I found that for USB3.0 it tries
>>>>> to reset the port before
>>>>> scanning. The comment says
>>>>>
>>>>> /* Is a USB 3.0 port in the Inactive or Compliance Mode state?
>>>>>     * Port warm reset is required to recover
>>>>>     */
>>>>>
>>>>> i. https://github.com/torvalds/linux/blob/master/drivers/usb/core/hub.c#L5736
>>>>> ii. https://github.com/torvalds/linux/blob/master/drivers/usb/core/hub.c#L2836
>>>>>
>>>>> I believe this isn't implemented in u-boot and hence explicit reset of
>>>>> a port fixes the issue.
>>>>
>>>> I feel this is separate issue and what needs to be fixed first is the
>>>> hard-wired VBus control.
>>>
>>> I beg to differ on this, couple of reasons for this
>>>
>>> 1. The same drive works fine without being reset on the USB2.0 ports - this
>>> confirms that the issue is related to USB3.0 only.
>>
>> This is a separate issue from the hard-wired VBus control. I agree the
>> issue does exist, I would simply like to avoid conflating the hard-wired
>> VBus control with device reset.
>>
>>> 2. Linux is able to detect the same drive on USB3.0 when u-boot fails - this
>>> confirms issue doesn't lie with regulator-always-on
>>
>> See above
>>
>>> 3. The links I pasted earlier mentions that in USB3.0 the ports need reset
>>> and this is done before the port is scanned. Adding the similar reset in u-boot
>>> fixes all with the same regulator-always-on. AFAIK u-boot doesn't handle
>>> this special USB3.0 case and maybe this is why I was finding a few posts
>>> around the drive not being detected in the USB3.0 port in u-boot but works in
>>> a USB2.0 port.
>>
>> I am not disputing the need for USB 3.0 device reset, I believe there
>> are two issues here -- one is the hard-wired VBus regulator -- the other
>> is this USB 3.0 reset. They should both be fixed.
> 
> Sure, agreed 100%.
> Do we need to fix both at the same time?
> Both patches seem to be independent.

Separate patch for the regulator please .