Re: musb: cppi41: broken high speed FTDI functionality when connected to musb directly

[Tony Lindgren <tony@atomide.com>]

* Yegor Yefremov <yegorslists@googlemail.com> [190930 08:20]:
> On Mon, Sep 30, 2019 at 8:59 AM Yegor Yefremov
> <yegorslists@googlemail.com> wrote:
> >
> > On Sat, Sep 28, 2019 at 6:09 PM Yegor Yefremov
> > <yegorslists@googlemail.com> wrote:
> > >
> > > On Fri, Sep 27, 2019 at 5:57 PM Tony Lindgren <tony@atomide.com> wrote:
> > > > Looks like I'm unable to reproduce this with bbb and FT232R
> > > > USB UART.
> > > >
> > > > I tried v5.3 with omap2plus_defconfig, then boot, load musb
> > > > and ftdi-sio modules, then connect ftdi directly to bbb,
> > > > and then run "minicom -D /dev/ttyUSB0" on bbb and it works
> > > > just fine for me.
> > > >
> > > > I tried also rebooting the device inbetween in case it only
> > > > happens on the first connect after boot but still no luck
> > > > reproducing.
> > >
> > > Strange. I've used a loopback to check whether the characters will be echoed.
> > > FTDI cable was connected all the time so that I could check RX right after boot.
> > > Both Buildroot and OpenWrt rootfs's showed this behaviour.
> > >
> > > > Maybe try adding some debug prints to cppi41_runtime_suspend()
> > > > and cppi41_runtime_resume() to see if gets runtime suspended
> > > > too early?
> > >
> > > Will do on Mo.
> >
> > I've added the printks to both routines and the result is quite
> > interesting. On the system with a directly attached FTDI both routines
> > will be always invoked before (resume) and after (suspend) the
> > test/minicom i.e. during the USB initialization.
> >
> > On the systems with a USB hub, these routines will be invoked only
> > during the USB initialization and the last invocation is resume.
> > During the test, there are no invocations.

Hmm OK thanks. Hard to say still based on that what might be missing.

I just tried also musb and phy built-in with FTDI connected on
boot, but still no luck reproducing the issue here.

> Removing PM routines workarounds the issue. Quick and dirty.
> 
>  static struct platform_driver cpp41_dma_driver = {
>           .probe  = cppi41_dma_probe,
>           .remove = cppi41_dma_remove,
>           .driver = {
>                   .name = "cppi41-dma-engine",
>                   /*.pm = &cppi41_pm_ops,*/
>                   .of_match_table = of_match_ptr(cppi41_dma_ids),
>           },
>   };

Well doing something like this to disable autosuspend might
be less intrusive until this one is fixed:

# echo on > /sys/bus/platform/drivers/musb-hdrc/musb-hdrc.1/power/control

But before that, maybe try with control set to auto, and increase the
autosuspend_delay_ms from 500 ms to let's say 2500 ms:

# echo 2500 > /sys/bus/platform/drivers/musb-hdrc/musb-hdrc.1/power/autosuspend_delay_ms

That is assuming the musb instance is 1 on your board, replace
with musb-hdrc.0 if a different interface from bbb.

Regards,

Tony