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

[Shantur Rathore]

On Mon, Dec 4, 2023 at 11:05 AM Marek Vasut <marex at denx.de> wrote:
>
> On 12/4/23 11:59, Shantur Rathore wrote:
> > Hi Marek,
> >
> > On Sun, Dec 3, 2023 at 10:37 PM Marek Vasut <marex at denx.de> wrote:
> >>
> >> 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 .
> >
> > Thanks, I am working on the regulator patch for rk3399-rockpro64-u-boot but
> > there seems to be a bug in the rk3399-rockpro64.dtsi from linux where
> > the typec phy
> > is configure with wrong regulator and if I do the patch as below
> >
> > --- a/arch/arm/dts/rk3399-rockpro64-u-boot.dtsi
> > +++ b/arch/arm/dts/rk3399-rockpro64-u-boot.dtsi
> > @@ -22,6 +22,23 @@
> >          };
> >   };
> >
> > +&vcc5v0_host {
> > +       /delete-property/ regulator-always-on;
> > +};
> > +
> > +&vcc5v0_typec {
> > +       /delete-property/ regulator-always-on;
> > +};
> > +
> > +&vcc5v0_usb {
> > +       /delete-property/ regulator-always-on;
> > +       /delete-property/ regulator-boot-on;
> > +};
> >
> > The typec port won't work until I correct the issue with
> >
> > +&u2phy1_host {
> > +       phy-supply = <&vcc5v0_typec>;
> > +};
> > +
> >
> > What would be acceptable here?
> > 1. Leave regulator for typec as it was
> > 2. disable regulator-always-on and fix phy here.
>
> Is there going to be a matching Linux kernel patch with a Linux side fix ?
>
> If so, include a link to that patch in lore.k.o in the commit message,
> and either temporarily fix it up in u-boot.dtsi or backport that patch
> to U-Boot DT, either works.

So there is no patch in lore.k.o for this and the more I looked the more
dts needed fixing related  usb. I would rather do it in one go and submit
proper patches to lore.k.o and u-boot.

For now, as usb reset is independent of the rockpro64 regulator issue, can
you please merge this and I will work on dts fixes separately.

Regards,
Shantur