[PATCH v2 0/4] USB-PD TCPM improvements

[Anand Moon]

Hi Sebastian,

On Mon, 3 Mar 2025 at 21:36, Sebastian Reichel
<sebastian.reichel at collabora.com> wrote:
>
> Hi Anand,
>
> On Mon, Mar 03, 2025 at 01:08:24PM +0530, Anand Moon wrote:
> > On Sat, 1 Mar 2025 at 23:41, Peter Robinson <pbrobinson at gmail.com> wrote:
> > > On Thu, 27 Feb 2025 at 06:01, Anand Moon <linux.amoon at gmail.com> wrote:
> > >> On Thu, 27 Feb 2025 at 00:15, Sebastian Reichel
> > >> <sebastian.reichel at collabora.com> wrote:
> > >> >
> > >> > Hi,
> > >> >
> > >> > I have a couple of fixes/improvements for the TCPM code. Three are fixing
> > >> > actual problems I noticed on the Rock 5B, which prevented booting up the
> > >> > system. One of them simply adds an error print before potentially committing
> > >> > hara-kiri by triggering a hard reset, which helps people understanding
> > >> > why their boards reset themself in case there are more problems. I've
> > >> > recently added the same print to the kernel TCPM code.
> > >> >
> > >> I have encountered issues with the Raspberry Pi Type C power
> > >> supply on a few occasions. Thanks for these changes, but it
> > >> dose not resolve the issue completely.
>
> I don't promise fixing all issues with this series. USB-PD is super
> complex. This series improves things and shouldn't have any
> regressions. It also helps with debugging further issues by having
> the extra print.
>
> > > I don't believe the RPi Type-C power supply supports power delivery.
> >
> > RPi 5 Type-C power supply is generally compatible with the Rock 5B
> > for daily use. I also have the Radxa 65W official Type-C power
> > supply for the Radxa Rock 5B board. I was checking the connection
> > messages with different power sources.
> >
> > >> Do you have plans to add a device tree node for this board?
> > >
> > > For which board?
> >
> > Radxa Rock 5B and Rock 5B+ indeed have a versatile USB Type-C port
> > that can be used both as a display port and a power source.
> >
> > During my investigation, I discovered that the Type-C port uses
> > the FCS,FUSB302 the driver instead of the TCPM driver. The
> > FUSB302 driver is specifically designed for USB Power Delivery
> > (USB PD) and supports various power delivery protocols.
>
> The fusb302 driver uses the TCPM framework. TCPM means "Type C Port
> Manager". The chip is not autonomous (like some other USB-PD chips).
> Without a driver telling it, what messages should be exchanged, it
> will stay quiet. TCPM implements the huge USB-PD state machine,
> which knows when a specific messages is expected or needs to be
> send. The remote side (i.e. the power-supply) has a similar state
> machine implemented. Ending up in a bad state in the state machine
> results in the system trying to do a hard reset to go back to the
> start. A hard reset involves removing the supply voltage and thus
> kills boards like the Rock 5B. To avoid this the state machine must
> be tweaked. That's why FUSB302 is not really mentioned here - the
> driver is passing the messages correctly. TCPM is the relevant bit,
> as that contains the state machine.
>
Ok, I agree with your changes,

However, I have a question regarding the Type-C controller's
connection to the PMIC via I2C.
I didn't see a corresponding controller node in the device tree source
(dts) file
that would support this function.

I feel this might be causing issues in maintaining the power state?

[1] https://github.com/u-boot/u-boot/blob/master/drivers/usb/tcpm/fusb302.c#L1285-L1316

> > As of now, I don't have a Type-C power source monitor to test the
> > feature
>
> You can also get debug information from the Rock 5B itself. But
> then you should make sure it has a backup power-supply (e.g. PoE
> or via the GPIO header), so that it does not reset itself when a
> USB-PD hard reset happens. Also this setup has some side-effects
> to the communication itself, since it affects the timings if you
> enable too much debug messages.
Yes, you are correct. I need to have a different setup to test this.
>
> Greetings,
>
> -- Sebastian
Thanks
-Anand