linux.git/drivers/tty/serial/8250, branch v6.1

Merge tag 'tty-6.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

2022-11-18T18:59:52+00:00

Pull tty/serial driver fixes from Greg KH:
 "Here are a number of small tty and serial driver fixes for 6.1-rc6.
  They all resolve reported problems:

   - kernel doc build problems with the -rc1 serial driver documentation
     update

   - n_gsm reported problems

   - imx serial driver missing callback

   - lots of tiny 8250 driver fixes for reported issues.

  All of these have been in linux-next for over a week with no reported
  problems"

* tag 'tty-6.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  docs/driver-api/miscellaneous: Remove kernel-doc of serial_core.c
  serial: 8250: Flush DMA Rx on RLSI
  serial: 8250_lpss: Use 16B DMA burst with Elkhart Lake
  serial: 8250_lpss: Configure DMA also w/o DMA filter
  serial: 8250: Fall back to non-DMA Rx if IIR_RDI occurs
  tty: n_gsm: fix sleep-in-atomic-context bug in gsm_control_send
  Revert "tty: n_gsm: replace kicktimer with delayed_work"
  Revert "tty: n_gsm: avoid call of sleeping functions from atomic context"
  serial: imx: Add missing .thaw_noirq hook
  tty: serial: fsl_lpuart: don't break the on-going transfer when global reset
  serial: 8250: omap: Flush PM QOS work on remove
  serial: 8250: omap: Fix unpaired pm_runtime_put_sync() in omap8250_remove()
  serial: 8250_omap: remove wait loop from Errata i202 workaround
  serial: 8250: omap: Fix missing PM runtime calls for omap8250_set_mctrl()
  serial: 8250: 8250_omap: Avoid RS485 RTS glitch on ->set_termios()

serial: 8250: Flush DMA Rx on RLSI

2022-11-09T12:04:39+00:00

Returning true from handle_rx_dma() without flushing DMA first creates
a data ordering hazard. If DMA Rx has handled any character at the
point when RLSI occurs, the non-DMA path handles any pending characters
jumping them ahead of those characters that are pending under DMA.

Fixes: 75df022b5f89 ("serial: 8250_dma: Fix RX handling")
Cc: 
Signed-off-by: Ilpo Järvinen 
Reviewed-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20221108121952.5497-5-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250_lpss: Use 16B DMA burst with Elkhart Lake

2022-11-09T12:04:39+00:00

Configure DMA to use 16B burst size with Elkhart Lake. This makes the
bus use more efficient and works around an issue which occurs with the
previously used 1B.

The fix was initially developed by Srikanth Thokala and Aman Kumar.
This together with the previous config change is the cleaned up version
of the original fix.

Fixes: 0a9410b981e9 ("serial: 8250_lpss: Enable DMA on Intel Elkhart Lake")
Cc:  # serial: 8250_lpss: Configure DMA also w/o DMA filter
Reported-by: Wentong Wu 
Signed-off-by: Ilpo Järvinen 
Reviewed-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20221108121952.5497-4-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250_lpss: Configure DMA also w/o DMA filter

2022-11-09T12:04:39+00:00

If the platform doesn't use DMA device filter (as is the case with
Elkhart Lake), whole lpss8250_dma_setup() setup is skipped. This
results in skipping also *_maxburst setup which is undesirable.
Refactor lpss8250_dma_setup() to configure DMA even if filter is not
setup.

Cc: stable 
Signed-off-by: Ilpo Järvinen 
Reviewed-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20221108121952.5497-3-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250: Fall back to non-DMA Rx if IIR_RDI occurs

2022-11-09T12:04:39+00:00

DW UART sometimes triggers IIR_RDI during DMA Rx when IIR_RX_TIMEOUT
should have been triggered instead. Since IIR_RDI has higher priority
than IIR_RX_TIMEOUT, this causes the Rx to hang into interrupt loop.
The problem seems to occur at least with some combinations of
small-sized transfers (I've reproduced the problem on Elkhart Lake PSE
UARTs).

If there's already an on-going Rx DMA and IIR_RDI triggers, fall
graciously back to non-DMA Rx. That is, behave as if IIR_RX_TIMEOUT had
occurred.

8250_omap already considers IIR_RDI similar to this change so its
nothing unheard of.

Fixes: 75df022b5f89 ("serial: 8250_dma: Fix RX handling")
Cc: 
Co-developed-by: Srikanth Thokala 
Signed-off-by: Srikanth Thokala 
Co-developed-by: Aman Kumar 
Signed-off-by: Aman Kumar 
Signed-off-by: Ilpo Järvinen 
Reviewed-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20221108121952.5497-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250: omap: Flush PM QOS work on remove

2022-11-03T02:44:43+00:00

Rebinding 8250_omap in a loop will at some point produce a warning for
kernel/power/qos.c:296 cpu_latency_qos_update_request() with error
"cpu_latency_qos_update_request called for unknown object". Let's flush
the possibly pending PM QOS work scheduled from omap8250_runtime_suspend()
before we disable runtime PM.

Fixes: 61929cf0169d ("tty: serial: Add 8250-core based omap driver")
Signed-off-by: Tony Lindgren 
Link: https://lore.kernel.org/r/20221028110044.54719-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250: omap: Fix unpaired pm_runtime_put_sync() in omap8250_remove()

2022-11-03T02:44:40+00:00

On remove, we get an error for "Runtime PM usage count underflow!". I guess
this driver is mostly built-in, and this issue has gone unnoticed for a
while. Somehow I did not catch this issue with my earlier fix done with
commit 4e0f5cc65098 ("serial: 8250_omap: Fix probe and remove for PM
runtime").

Fixes: 4e0f5cc65098 ("serial: 8250_omap: Fix probe and remove for PM runtime")
Signed-off-by: Tony Lindgren 
Depends-on: dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
Link: https://lore.kernel.org/r/20221028105813.54290-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250_omap: remove wait loop from Errata i202 workaround

2022-11-03T02:44:35+00:00

We were occasionally seeing the "Errata i202: timedout" on an AM335x
board when repeatedly opening and closing a UART connected to an active
sender. As new input may arrive at any time, it is possible to miss the
"RX FIFO empty" condition, forcing the loop to wait until it times out.

Nothing in the i202 Advisory states that such a wait is even necessary;
other FIFO clear functions like serial8250_clear_fifos() do not wait
either. For this reason, it seems safe to remove the wait, fixing the
mentioned issue.

Fixes: 61929cf0169d ("tty: serial: Add 8250-core based omap driver")
Reviewed-by: Ilpo Järvinen 
Signed-off-by: Matthias Schiffer 
Link: https://lore.kernel.org/r/20221013112339.2540767-1-matthias.schiffer@ew.tq-group.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250: omap: Fix missing PM runtime calls for omap8250_set_mctrl()

2022-11-03T02:44:27+00:00

There are cases where omap8250_set_mctrl() may get called after the
UART has already autoidled causing an asynchronous external abort.

This can happen on ttyport_open():

mem_serial_in from omap8250_set_mctrl+0x38/0xa0
omap8250_set_mctrl from uart_update_mctrl+0x4c/0x58
uart_update_mctrl from uart_dtr_rts+0x60/0xa8
uart_dtr_rts from tty_port_block_til_ready+0xd0/0x2a8
tty_port_block_til_ready from uart_open+0x14/0x1c
uart_open from ttyport_open+0x64/0x148

And on ttyport_close():

omap8250_set_mctrl from uart_update_mctrl+0x3c/0x48
uart_update_mctrl from uart_dtr_rts+0x54/0x9c
uart_dtr_rts from tty_port_shutdown+0x78/0x9c
tty_port_shutdown from tty_port_close+0x3c/0x74
tty_port_close from ttyport_close+0x40/0x58

It can also happen on disassociate_ctty() calling uart_shutdown()
that ends up calling omap8250_set_mctrl().

Let's fix the issue by adding missing PM runtime calls to
omap8250_set_mctrl(). To do this, we need to add __omap8250_set_mctrl()
that can be called from both omap8250_set_mctrl(), and from runtime PM
resume path when restoring the registers.

Fixes: 61929cf0169d ("tty: serial: Add 8250-core based omap driver")
Reported-by: Merlijn Wajer 
Reported-by: Romain Naour 
Reported-by: Ivaylo Dimitrov 
Tested-by: Ivaylo Dimitrov 
Signed-off-by: Tony Lindgren 
Depends-on: dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
Link: https://lore.kernel.org/r/20221024063613.25943-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman

serial: 8250: 8250_omap: Avoid RS485 RTS glitch on ->set_termios()

2022-11-03T02:44:04+00:00

RS485-enabled UART ports on TI Sitara SoCs with active-low polarity
exhibit a Transmit Enable glitch on ->set_termios():

omap8250_restore_regs(), which is called from omap_8250_set_termios(),
sets the TCRTLR bit in the MCR register and clears all other bits,
including RTS.  If RTS uses active-low polarity, it is now asserted
for no reason.

The TCRTLR bit is subsequently cleared by writing up->mcr to the MCR
register.  That variable is always zero, so the RTS bit is still cleared
(incorrectly so if RTS is active-high).

(up->mcr is not, as one might think, a cache of the MCR register's
current value.  Rather, it only caches a single bit of that register,
the AFE bit.  And it only does so if the UART supports the AFE bit,
which OMAP does not.  For details see serial8250_do_set_termios() and
serial8250_do_set_mctrl().)

Finally at the end of omap8250_restore_regs(), the MCR register is
restored (and RTS deasserted) by a call to up->port.ops->set_mctrl()
(which equals serial8250_set_mctrl()) and serial8250_em485_stop_tx().

So there's an RTS glitch between setting TCRTLR and calling
serial8250_em485_stop_tx().  Avoid by using a read-modify-write
when setting TCRTLR.

While at it, drop a redundant initialization of up->mcr.  As explained
above, the variable isn't used by the driver and it is already
initialized to zero because it is part of the static struct
serial8250_ports[] declared in 8250_core.c.  (Static structs are
initialized to zero per section 6.7.8 nr. 10 of the C99 standard.)

Cc: Jan Kiszka 
Cc: Su Bao Cheng 
Tested-by: Matthias Schiffer 
Signed-off-by: Lukas Wunner 
Link: https://lore.kernel.org/r/6554b0241a2c7fd50f32576fdbafed96709e11e8.1664278942.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman