Re: WARNING around serdev/bt/btnxpuart with 6.7-rc2

[Francesco Dolcini]

On Mon, Nov 27, 2023 at 08:49:28AM +0000, Neeraj sanjay kale wrote:
> > On Fri, Nov 24, 2023 at 09:33:09PM +0100, Francesco Dolcini wrote:
> > > Hello all,
> > > while doing some test with current [1] Linux mainline I randomly hit a
> > > warning. It is not systematic and I cannot really tell when it was
> > > introduced, posting here to collect some ideas.
> > >
> > > Amitkumar, Neeraj: to me the issue is around the bluetooth/btnxpuart
> > > driver, however I could also be plain wrong.
> > >
> > > The issue was reproduced on a Toradex Verdin AM62 [2] that is based on
> > > a TI
> > > AM625 SOC (arm64) running with a arm64 defconfig and built with GCC 9
> > [3].
> > >
> > > [    9.599027] Loaded X.509 cert 'sforshee: 00b28ddf47aef9cea7'
> > > [    9.962266] Bluetooth: hci0: Frame reassembly failed (-84)
> > > [    9.972939] ------------[ cut here ]------------
> > > [    9.977922] serial serial0: receive_buf returns -84 (count = 6)
> > > [    9.994857] WARNING: CPU: 0 PID: 37 at drivers/tty/serdev/serdev-
> > ttyport.c:37 ttyport_receive_buf+0xd8/0xf8
> > > [   10.004840] Modules linked in: mwifiex_sdio(+) mwifiex
> > snd_soc_simple_card crct10dif_ce cfg80211 snd_soc_simple_card_utils
> > k3_j72xx_bandgap rti_wdt rtc_ti_k3 btnxpuart bluetooth sa2ul ecdh_generic
> > ecc sha256_generic tidss rfkill libsha256 drm_dma_helper
> > snd_soc_davinci_mcasp authenc omap_mailbox snd_soc_ti_udma
> > snd_soc_ti_edma snd_soc_ti_sdma atmel_mxt_ts ina2xx snd_soc_nau8822
> > ti_sn65dsi83 tc358768 ti_ads1015 tps65219_pwrbutton at24 m_can_platform
> > industrialio_triggered_buffer drm_kms_helper m_can kfifo_buf rtc_ds1307
> > lm75 pwm_tiehrpwm can_dev spi_omap2_mcspi panel_lvds pwm_bl
> > libcomposite fuse drm backlight ipv6
> > > [   10.059984] CPU: 0 PID: 37 Comm: kworker/u4:2 Not tainted 6.7.0-rc2-
> > 00147-gf1a09972a45a #1
> > > [   10.071793] Hardware name: Toradex Verdin AM62 WB on Verdin
> > Development Board (DT)
> > > [   10.082898] Workqueue: events_unbound flush_to_ldisc
> > > [   10.091345] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS
> > BTYPE=--)
> > > [   10.101820] pc : ttyport_receive_buf+0xd8/0xf8
> > > [   10.109712] lr : ttyport_receive_buf+0xd8/0xf8
> > > [   10.117581] sp : ffff800082b9bd20
> > > [   10.124202] x29: ffff800082b9bd20 x28: ffff00000000ee05 x27:
> > ffff0000002f21c0
> > > [   10.134735] x26: ffff000002931820 x25: 61c8864680b583eb x24:
> > ffff0000002f21b8
> > > [   10.145209] x23: ffff00000026e740 x22: ffff0000002f21e0 x21:
> > ffffffffffffffac
> > > [   10.155686] x20: ffff000000da5c00 x19: 0000000000000006 x18:
> > 0000000000000000
> > > [   10.166178] x17: ffff7fffbe0e7000 x16: ffff800080000000 x15:
> > 000039966db1c650
> > > [   10.176564] x14: 000000000000022c x13: 000000000000022c x12:
> > 0000000000000000
> > > [   10.186979] x11: 000000000000000a x10: 0000000000000a60 x9 :
> > ffff800082b9bb80
> > > [   10.197352] x8 : ffff00000026f200 x7 : ffff00003fd90080 x6 :
> > 00000000000022e5
> > > [   10.207680] x5 : 00000000410fd030 x4 : 0000000000c0000e x3 :
> > ffff7fffbe0e7000
> > > [   10.218051] x2 : 0000000000000002 x1 : 0000000000000000 x0 :
> > 0000000000000000
> > > [   10.228393] Call trace:
> > > [   10.233989]  ttyport_receive_buf+0xd8/0xf8
> > > [   10.241224]  flush_to_ldisc+0xbc/0x1a4
> > > [   10.248117]  process_scheduled_works+0x16c/0x28c
> > > [   10.255851]  worker_thread+0x16c/0x2e0
> > > [   10.262673]  kthread+0x11c/0x128
> > > [   10.268953]  ret_from_fork+0x10/0x20
> > > [   10.275460] ---[ end trace 0000000000000000 ]---
> > > [   10.294674] Bluetooth: hci0: Frame reassembly failed (-84)
> > > [   10.461657] Bluetooth: hci0: Frame reassembly failed (-84)
> > > [   10.472025] Bluetooth: hci0: Frame reassembly failed (-84)
> > 
> > I think that what is happening is the following:
> > 
> >  -> serdev-ttyport.c:ttyport_receive_buf()
> >    -> btnxpuart.c:btnxpuart_receive_buf()
> >       -> h4_recv_buf() errors out
> >       -> return -84
> >    -> warn because ret is <0
> > 
> > Is this the desired behavior? If I understand correct recv_buf() is supposed to
> > return how many bytes it has consumed, e.g. something from 0 to count.
> However, if there is a packet corruption, or the payload length in
> received header, and actual payload are not equal, or wrong sequence
> is received or there is a probable baudrate mismatch, it returns an
> error (<0).
yes, what the code is doing is clear, however from this email thread I
understand that this is wrong. I'll send a patch to fix this.

> In this case, -84 is illegal sequence error.
> 
> It would help if you could share with us some more info:
> 1) Test steps.
just powering up the board, nothing else. it's a toradex verdin am62
(device tree available in mainline kernel).

> 3) Is PDn pin toggled? If yes, then chip is probably sending out
> bootloader signatures at 115200, while host UART is at 3000000.

I would not be surprise if this was because of the PDn pin, the signal
is shared between wi-fi and bt, but only the wi-fi part is aware of it
and the firmware loaded is the combo one.

Depending on the load order it could just fails.

See also https://lore.kernel.org/all/dca8bc7fec5f527cac2e280cd8ed4edae1f473ea.camel@xxxxxxxxxxx/

With that said my concern here is not that is failing, is that I have 
a kernel warning, and this seems just a mistake in the code.

Francesco