[PATCH v3 0/7] FUSB302 USB-C controller support

[Sebastian Reichel]

Hi,

On Mon, Aug 19, 2024 at 07:08:37PM GMT, Marek Vasut wrote:
> On 8/18/24 11:43 PM, Jonas Karlman wrote:
> > > > On ROCK 5B power is usually supplied via it's USB-C port. This port has the
> > > > data lines connected to RK3588, VBUS connected to the input regulator and
> > > > CC pins connected to FUSB302. FUSB302 is a USB-C controller, which can be
> > > > accessed via I2C from RK3588. The USB-C controller is needed to figure out
> > > > the USB-C cable orientation, but also to do USB PD communication. Thus it
> > > > would be great to enable support for it in the operating system.
> > > > 
> > > > But the USB-PD specification requires, that a device reacts to USB-PD messages
> > > > send by the power-supply within around 5 seconds. If that does not happen the
> > > > power-supply assumes, that the device does not support USB-PD. If a device
> > > > later starts sending USB-PD messages it is considered an error, which is solved
> > > > by doing a hard reset. A USB-PD hard reset means, that all supply voltages are
> > > > removed for a short period of time. For boards, which are solely powered
> > > > through their USB-C port, like the Radxa Rock 5B, this results in an machine
> > > > reset. This is currently worked around by not describing the FUSB302 in the
> > > > kernel DT, so nothing will ever speak USB-PD on the Rock 5B. This means
> > > > 
> > > > 1. the USB-C port cannot be used at all
> > > > 2. the board will be running via fallback supply, which provides limited
> > > >      power capabilities
> > > > 
> > > > In order to avoid the hard reset, this adds FUSB302 support to U-Boot, so
> > > > that we react to the power-supply's queries in time. The code, which is
> > > > originally from the Linux kernel, consists of two parts:
> > > > 
> > > > 1. the tcpm state machine, which implements the Type C port manager state
> > > >      machine as described in the USB PD specification
> > > > 2. the fusb302 driver, which knows about specific registers
> > > > 
> > > > Especially the first part has been heavily modified compared to the
> > > > kernel, which makes use of multiple delayed works and threads. For this
> > > > I used a priorly ported version from Rockchip, removed their hacks and
> > > > any states not necessary in U-Boot (e.g. audio accessory support).
> > > > 
> > > > Sorry for the delay in getting PATCHv3 ready.
> > > 
> > > I am the one who should be sorry here, really, sorry for the abysmal
> > > delay in my replies.
> > > 
> > > So ... this series looks good to me. Thank you for working on this !
> > > 
> > > Jonas, are your concerns resolved ?
> > 
> > No, for ROCK 5B the full overwrite of the Rockchip common misc_init_r()
> > in mach-rockchip/board.c should be fixed, rockchip_early_misc_init_r()
> > could probably be used instead (or possible a PREBOOT cmd), see [1].
> 
> Can you use DM_FLAG_PROBE_AFTER_BIND instead of misc_init_r for this ?
> 
> drivers/led/led-uclass.c: dev_or_flags(dev, DM_FLAG_PROBE_AFTER_BIND);
> 
> This will probe the driver after it got bound, and you won't have to hack
> around board files or arch files for this.

Jonas suggested the same. My response still applies:

Depending on the remote side (i.e. the power-supply) the TCPM state
machine can take quite some time to get it into the "final" state.
The worst I have seen was around 2 seconds.

Boards, which are not powered via their TCPM controller can survive
a USB hard reset and do not need any U-Boot support. I think we do
not want to add this penality to these boards.

Greetings,

-- Sebastian
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