On Sat, Sep 28, 2019 at 6:09 PM Yegor Yefremov
<yegorsli...@googlemail.com> wrote:
>
> On Fri, Sep 27, 2019 at 5:57 PM Tony Lindgren <t...@atomide.com> wrote:
> >
> > * Tony Lindgren <t...@atomide.com> [190927 15:20]:
> > > * Yegor Yefremov <yegorsli...@googlemail.com> [190927 12:31]:
> > > > On Fri, Sep 27, 2019 at 10:18 AM Yegor Yefremov
> > > > <yegorsli...@googlemail.com> wrote:
> > > > >
> > > > > I was porting my system from 3.18/4.2 to 5.3. During this process I
> > > > > noticed that FT4232 that is attached directly to musb is not working
> > > > > correctly when opened for the first time: tx is working but nothing
> > > > > can be received. On the second opening everything is working fine.
> > > > > When the same chip is connected via a USB hub - everything is working
> > > > > from the very beginning.
> > > > >
> > > > > I could reproduce this issue using BeagleBone Black with
> > > > > omap2plus_defconfig.
> > > > >
> > > > > # lsusb -t
> > > > > +/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=musb-hdrc/1p, 480M
> > > > > |__ Port 1: Dev 2, If 0, Class=, Driver=ftdi_sio, 480M
> > > > > |__ Port 1: Dev 2, If 1, Class=, Driver=ftdi_sio, 480M
> > > > > |__ Port 1: Dev 2, If 2, Class=, Driver=ftdi_sio, 480M
> > > > > |__ Port 1: Dev 2, If 3, Class=, Driver=ftdi_sio, 480M
> > > > >
> > > > > git bisect revealed the following:
> > > > >
> > > > > fdea2d09b997ba4c86e7a707a5fac87c305f2131 is the first bad commit
> > > > > commit fdea2d09b997ba4c86e7a707a5fac87c305f2131
> > > > > Author: Tony Lindgren <t...@atomide.com>
> > > > > Date: Wed Aug 31 07:19:59 2016 -0700
> > > > >
> > > > > dmaengine: cppi41: Add basic PM runtime support
> > > > >
> > > > > Let's keep the device enabled between cppi41_dma_issue_pending()
> > > > > and dmaengine_desc_get_callback_invoke() and rely on the PM
> > > > > runtime
> > > > > autoidle timeout elsewhere.
> > > > >
> > > > > As the PM runtime is for whole device, not for each channel,
> > > > > we need to queue pending transfers if the device is PM runtime
> > > > > suspended. Then we start the pending transfers in PM runtime
> > > > > resume.
> > > > >
> > > > > Signed-off-by: Tony Lindgren <t...@atomide.com>
> > > > > Signed-off-by: Vinod Koul <vinod.k...@intel.com>
> > > > >
> > > > > :040000 040000 8cf92c09083541dfdee01cc2973e73ef520f4fb1
> > > > > a03c1a7ba8e723f7b503733c46edaa4141483265 M drivers
> > > > >
> > > > > Any idea?
> > > >
> > > > The problems can be reproduced with other FTDI chips like FT232R.
> > > >
> > > > Invoking "minicom -D /dev/ttyUSB0" and typing some characters is
> > > > enough to reproduce the issue (just in case, hw flow control should be
> > > > disabled).
> > > >
> > > > cp210x based converter is working without an issue. So only FTDI chips
> > > > are affected so far.
> > >
> > > Hmm OK. Maybe this could be an issue where the FTDI chip takes
> > > longer to enumerate and cppi41 is already suspended by then?
> > >
> > > At least we had a similar issue with commit ae4a3e028bb8
> > > ("dmaengine: cppi41: Fix runtime PM timeouts with USB mass
> > > storage").
> >
> > 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.
Regards,
Yegor
