The LS1028A has six LPUART controllers. Add the nodes.

This was tested on a custom board.
Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20200307091302.14881-2-michael@walle.ccSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add the LS1028A SoC compatibility string to the lpuart devicetree
bindings documentation.
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200307091302.14881-1-michael@walle.ccSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add a early_console_setup() for the LS1028A SoC with 32bit, little
endian access. If the bootloader does a fixup of the clock-frequency
node the baudrate divisor register will automatically be set.
Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20200306214433.23215-5-michael@walle.ccSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The LS1028A uses little endian register access and has a different FIFO
size encoding.
Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20200306214433.23215-4-michael@walle.ccSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Use the correct device to request the DMA mapping. Otherwise the IOMMU
doesn't get the mapping and it will generate a page fault.

The error messages look like:
[   19.012140] arm-smmu 5000000.iommu: Unhandled context fault: fsr=0x402, iova=0xbbfff800, fsynr=0x3e0021, cbfrsynra=0x828, cb=9
[   19.023593] arm-smmu 5000000.iommu: Unhandled context fault: fsr=0x402, iova=0xbbfff800, fsynr=0x3e0021, cbfrsynra=0x828, cb=9

This was tested on a custom board with a LS1028A SoC.
Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20200306214433.23215-3-michael@walle.ccSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The DMA channel might not be available at probe time. This is esp. the
case if the DMA controller has an IOMMU mapping.

There is also another caveat. If there is no DMA controller at all,
dma_request_chan() will also return -EPROBE_DEFER. Thus we cannot test
for -EPROBE_DEFER in probe(). Otherwise the lpuart driver will fail to
probe if, for example, the DMA driver is not enabled in the kernel
configuration.

To workaround this, we request the DMA channel in _startup(). Other
serial drivers do it the same way.
Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20200306214433.23215-2-michael@walle.ccSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

To make it more obvious what almost everyone wants to set here.

Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Joe Perches <joe@perches.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vasiliy Khoruzhick <vasilykh@arista.com>
Cc: linux-serial@vger.kernel.org
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200306153156.579921-1-dima@arista.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Use uart_console() helper in instead of open coded variant.

Note, SERIAL_CORE_CONSOLE is selected by SERIAL_ATMEL_CONSOLE,
thus no functional changes expected.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Link: https://lore.kernel.org/r/20200310133057.86840-1-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Use uart_console() helper in instead of open coded variant.

Note, SERIAL_CORE_CONSOLE is selected by SERIAL_PIC32_CONSOLE,
thus no functional changes expected.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200311090027.64441-1-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

SiFive's UART has a software controller clock divider that produces the
final baud rate clock.  Whenever the clock that drives the UART is
changed this divider must be updated accordingly, and given that these
two events are controlled by software they cannot be done atomically.
During the period between updating the UART's driving clock and internal
divider the UART will transmit a different baud rate than what the user
has configured, which will probably result in a corrupted transmission
stream.

The SiFive UART has a FIFO, but due to an issue with the programming
interface there is no way to directly determine when the UART has
finished transmitting.  We're essentially restricted to dead reckoning
in order to figure that out: we can use the FIFO's TX busy register to
figure out when the last frame has begun transmission and just delay for
a long enough that the last frame is guaranteed to get out.

As far as the actual implementation goes: I've modified the existing
existing clock notifier function to drain both the FIFO and the shift
register in on PRE_RATE_CHANGE.  As far as I know there is no hardware
flow control in this UART, so there's no good way to ask the other end
to stop transmission while we can't receive (inserting software flow
control messages seems like a bad idea here).
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Tested-by: Yash Shah <yash.shah@sifive.com>
Link: https://lore.kernel.org/r/20200307042637.83728-1-palmer@dabbelt.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

We need the vt fixes in here and it resolves a merge issue with
drivers/tty/vt/selection.c
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull ARM SoC fixes from Olof Johansson:
 "We've been accruing these for a couple of weeks, so the batch is a bit
  bigger than usual.

  Largest delta is due to a led-bl driver that is added -- there was a
  miscommunication before the merge window and the driver didn't make it
  in. Due to this, the platforms needing it regressed. At this point, it
  seemed easier to add the new driver than unwind the changes.

  Besides that, there are a handful of various fixes:

   - AMD tee memory leak fix

   - A handful of fixlets for i.MX SCU communication

   - A few maintainers woke up and realized DEBUG_FS had been missing
     for a while, so a few updates of that.

  ... and the usual collection of smaller fixes to various platforms"

* tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (37 commits)
  ARM: socfpga_defconfig: Add back DEBUG_FS
  arm64: dts: socfpga: agilex: Fix gmac compatible
  ARM: bcm2835_defconfig: Explicitly restore CONFIG_DEBUG_FS
  arm64: dts: meson: fix gxm-khadas-vim2 wifi
  arm64: dts: meson-sm1-sei610: add missing interrupt-names
  ARM: meson: Drop unneeded select of COMMON_CLK
  ARM: dts: bcm2711: Add pcie0 alias
  ARM: dts: bcm283x: Add missing properties to the PWR LED
  tee: amdtee: fix memory leak in amdtee_open_session()
  ARM: OMAP2+: Fix compile if CONFIG_HAVE_ARM_SMCCC is not set
  arm: dts: dra76x: Fix mmc3 max-frequency
  ARM: dts: dra7: Add "dma-ranges" property to PCIe RC DT nodes
  bus: ti-sysc: Fix 1-wire reset quirk
  ARM: dts: r8a7779: Remove deprecated "renesas, rcar-sata" compatible value
  soc: imx-scu: Align imx sc msg structs to 4
  firmware: imx: Align imx_sc_msg_req_cpu_start to 4
  firmware: imx: scu-pd: Align imx sc msg structs to 4
  firmware: imx: misc: Align imx sc msg structs to 4
  firmware: imx: scu: Ensure sequential TX
  ARM: dts: imx7-colibri: Fix frequency for sd/mmc
  ...

Pull EDAC fix from Borislav Petkov:
 "Error reporting fix for synopsys_edac: do not overwrite partial
  decoded error message (Sherry Sun)"

* tag 'edac_urgent-2020-03-08' of git://git.kernel.org/pub/scm/linux/kernel/git/ras/ras:
  EDAC/synopsys: Do not print an error with back-to-back snprintf() calls

Pull char/misc fixes from Greg KH:
 "Here are four small char/misc driver fixes for reported issues for
  5.6-rc5.

  These fixes are:

   - binder fix for a potential use-after-free problem found (took two
     tries to get it right)

   - interconnect core fix

   - altera-stapl driver fix

  All four of these have been in linux-next for a while with no reported
  issues"

* tag 'char-misc-5.6-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  binder: prevent UAF for binderfs devices II
  interconnect: Handle memory allocation errors
  altera-stapl: altera_get_note: prevent write beyond end of 'key'
  binder: prevent UAF for binderfs devices

Pull driver core and debugfs fixes from Greg KH:
 "Here are four small driver core / debugfs patches for 5.6-rc3:

   - debugfs api cleanup now that all debugfs_create_regset32() callers
     have been fixed up. This was waiting until after the -rc1 merge as
     these fixes came in through different trees

   - driver core sync state fixes based on reports of minor issues found
     in the feature

  All of these have been in linux-next with no reported issues"

* tag 'driver-core-5.6-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  driver core: Skip unnecessary work when device doesn't have sync_state()
  driver core: Add dev_has_sync_state()
  driver core: Call sync_state() even if supplier has no consumers
  debugfs: remove return value of debugfs_create_regset32()

Pull tty/serial fixes from Greg KH:
 "Here are some small tty/serial fixes for 5.6-rc5

  Just some small serial driver fixes, and a vt core fixup, full details
  are:

   - vt fixes for issues found by syzbot

   - serdev fix for Apple boxes

   - fsl_lpuart serial driver fixes

   - MAINTAINER update for incorrect serial files

   - new device ids for 8250_exar driver

   - mvebu-uart fix

  All of these have been in linux-next with no reported issues"

* tag 'tty-5.6-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  tty: serial: fsl_lpuart: free IDs allocated by IDA
  Revert "tty: serial: fsl_lpuart: drop EARLYCON_DECLARE"
  serdev: Fix detection of UART devices on Apple machines.
  MAINTAINERS: Add missed files related to Synopsys DesignWare UART
  serial: 8250_exar: add support for ACCES cards
  tty:serial:mvebu-uart:fix a wrong return
  vt: selection, push sel_lock up
  vt: selection, push console lock down

Pull USB/PHY fixes from Greg KH:
 "Here are some small USB and PHY driver fixes for reported issues for
  5.6-rc5.

  Included in here are:

   - phy driver fixes

   - new USB quirks

   - USB cdns3 gadget driver fixes

   - USB hub core fixes

  All of these have been in linux-next with no reported issues"

* tag 'usb-5.6-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  usb: dwc3: gadget: Update chain bit correctly when using sg list
  usb: core: port: do error out if usb_autopm_get_interface() fails
  usb: core: hub: do error out if usb_autopm_get_interface() fails
  usb: core: hub: fix unhandled return by employing a void function
  usb: storage: Add quirk for Samsung Fit flash
  usb: quirks: add NO_LPM quirk for Logitech Screen Share
  usb: usb251xb: fix regulator probe and error handling
  phy: allwinner: Fix GENMASK misuse
  usb: cdns3: gadget: toggle cycle bit before reset endpoint
  usb: cdns3: gadget: link trb should point to next request
  phy: mapphone-mdm6600: Fix timeouts by adding wake-up handling
  phy: brcm-sata: Correct MDIO operations for 40nm platforms
  phy: ti: gmii-sel: do not fail in case of gmii
  phy: ti: gmii-sel: fix set of copy-paste errors
  phy: core: Fix phy_get() to not return error on link creation failure
  phy: mapphone-mdm6600: Fix write timeouts with shorter GPIO toggle interval

Pull rdma fixes from Jason Gunthorpe:
 "Nothing particularly exciting, some small ODP regressions from the mmu
  notifier rework, another bunch of syzkaller fixes, and a bug fix for a
  botched syzkaller fix in the first rc pull request.

   - Fix busted syzkaller fix in 'get_new_pps' - this turned out to
     crash on certain HW configurations

   - Bug fixes for various missed things in error unwinds

   - Add a missing rcu_read_lock annotation in hfi/qib

   - Fix two ODP related regressions from the recent mmu notifier
     changes

   - Several more syzkaller bugs in siw, RDMA netlink, verbs and iwcm

   - Revert an old patch in CMA as it is now shown to not be allocating
     port numbers properly"

* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma:
  RDMA/iwcm: Fix iwcm work deallocation
  RDMA/siw: Fix failure handling during device creation
  RDMA/nldev: Fix crash when set a QP to a new counter but QPN is missing
  RDMA/odp: Ensure the mm is still alive before creating an implicit child
  RDMA/core: Fix protection fault in ib_mr_pool_destroy
  IB/mlx5: Fix implicit ODP race
  IB/hfi1, qib: Ensure RCU is locked when accessing list
  RDMA/core: Fix pkey and port assignment in get_new_pps
  RMDA/cm: Fix missing ib_cm_destroy_id() in ib_cm_insert_listen()
  RDMA/rw: Fix error flow during RDMA context initialization
  RDMA/core: Fix use of logical OR in get_new_pps
  Revert "RDMA/cma: Simplify rdma_resolve_addr() error flow"

Pull io_uring fixes from Jens Axboe:
 "Here are a few io_uring fixes that should go into this release. This
  contains:

   - Removal of (now) unused io_wq_flush() and associated flag (Pavel)

   - Fix cancelation lockup with linked timeouts (Pavel)

   - Fix for potential use-after-free when freeing percpu ref for fixed
     file sets

   - io-wq cancelation fixups (Pavel)"

* tag 'io_uring-5.6-2020-03-07' of git://git.kernel.dk/linux-block:
  io_uring: fix lockup with timeouts
  io_uring: free fixed_file_data after RCU grace period
  io-wq: remove io_wq_flush and IO_WQ_WORK_INTERNAL
  io-wq: fix IO_WQ_WORK_NO_CANCEL cancellation

Pull block fixes from Jens Axboe:
 "Here are a few fixes that should go into this release. This contains:

   - Revert of a bad bcache patch from this merge window

   - Removed unused function (Daniel)

   - Fixup for the blktrace fix from Jan from this release (Cengiz)

   - Fix of deeper level bfqq overwrite in BFQ (Carlo)"

* tag 'block-5.6-2020-03-07' of git://git.kernel.dk/linux-block:
  block, bfq: fix overwrite of bfq_group pointer in bfq_find_set_group()
  blktrace: fix dereference after null check
  Revert "bcache: ignore pending signals when creating gc and allocator thread"
  block: Remove used kblockd_schedule_work_on()

Pull media fixes from Mauro Carvalho Chehab:

 - a fix for the media controller links in both hantro driver and in
   v4l2-mem2mem core

 - some fixes for the pulse8-cec driver

 - vicodec: handle alpha channel for RGB32 formats, as it may be used

 - mc-entity.c: fix handling of pad flags

* tag 'media/v5.6-2' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
  media: hantro: Fix broken media controller links
  media: mc-entity.c: use & to check pad flags, not ==
  media: v4l2-mem2mem.c: fix broken links
  media: vicodec: process all 4 components for RGB32 formats
  media: pulse8-cec: close serio in disconnect, not adap_free
  media: pulse8-cec: INIT_DELAYED_WORK was called too late

There is a recipe to deadlock the kernel: submit a timeout sqe with a
linked_timeout (e.g.  test_single_link_timeout_ception() from liburing),
and SIGKILL the process.

Then, io_kill_timeouts() takes @ctx->completion_lock, but the timeout
isn't flagged with REQ_F_COMP_LOCKED, and will try to double grab it
during io_put_free() to cancel the linked timeout. Probably, the same
can happen with another io_kill_timeout() call site, that is
io_commit_cqring().
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull s390 fixes from Vasily Gorbik:

 - Fix panic in gup_fast on large pud by providing an implementation of
   pud_write. This has been overlooked during migration to common gup
   code.

 - Fix unexpected write combining on PCI stores.

* tag 's390-5.6-5' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/pci: Fix unexpected write combine on resource
  s390/mm: fix panic in gup_fast on large pud

Pull powerpc fixes from Michael Ellerman:
 "Some more powerpc fixes for 5.6:

   - One fix for a recent regression to our breakpoint/watchpoint code.

   - Another fix for our KUAP support, this time a missing annotation in
     a rarely used path in signal handling.

   - A fix for our handling of a CPU feature that effects the PMU, when
     booting guests in some configurations.

   - A minor fix to our linker script to explicitly include the .BTF
     section.

  Thanks to: Christophe Leroy, Desnes A. Nunes do Rosario, Leonardo
  Bras, Naveen N. Rao, Ravi Bangoria, Stefan Berger"

* tag 'powerpc-5.6-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/mm: Fix missing KUAP disable in flush_coherent_icache()
  powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems
  powerpc: Include .BTF section
  powerpc/watchpoint: Don't call dar_within_range() for Book3S

Pull xen fixes from Juergen Gross:
 "Four fixes and a small cleanup patch:

   - two fixes by Dongli Zhang fixing races in the xenbus driver

   - two fixes by me fixing issues introduced in 5.6

   - a small cleanup by Gustavo Silva replacing a zero-length array with
     a flexible-array"

* tag 'for-linus-5.6b-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/blkfront: fix ring info addressing
  xen/xenbus: fix locking
  xenbus: req->err should be updated before req->state
  xenbus: req->body should be updated before req->state
  xen: Replace zero-length array with flexible-array member

Pull thread fixes from Christian Brauner:
 "Here are a few hopefully uncontroversial fixes:

   - Use RCU_INIT_POINTER() when initializing rcu protected members in
     task_struct to fix sparse warnings.

   - Add pidfd_fdinfo_test binary to .gitignore file"

* tag 'for-linus-2020-03-07' of gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux:
  selftests: pidfd: Add pidfd_fdinfo_test in .gitignore
  exit: Fix Sparse errors and warnings
  fork: Use RCU_INIT_POINTER() instead of rcu_access_pointer()

Pull sound fixes from Takashi Iwai:
 "The regular "bump-in-the-middle" updates, containing mostly ASoC-
  related fixes at this time. All changes are reasonably small.

  A few entries are for ASoC and ALSA core parts (DAPM, PCM, topology)
  for followups of the recent changes and potential buffer overflow by
  snprintf(), while the rest are (both new and old) device-specific
  fixes for Intel, meson, tas2562, rt1015, as well as the usual HD-audio
  quirks"

* tag 'sound-5.6-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound: (25 commits)
  ALSA: sgio2audio: Remove usage of dropped hw_params/hw_free functions
  ALSA: hda/realtek - Enable the headset of ASUS B9450FA with ALC294
  ALSA: hda/realtek - Fix silent output on Gigabyte X570 Aorus Master
  ALSA: hda/realtek - Add Headset Button supported for ThinkPad X1
  ALSA: hda/realtek - Add Headset Mic supported
  ASoC: wm8741: Fix typo in Kconfig prompt
  ASoC: stm32: sai: manage rebind issue
  ASoC: SOF: Fix snd_sof_ipc_stream_posn()
  ASoC: rt1015: modify pre-divider for sysclk
  ASoC: rt1015: add operation callback function for rt1015_dai[]
  ASoC: soc-component: tidyup snd_soc_pcm_component_sync_stop()
  ASoC: dapm: Correct DAPM handling of active widgets during shutdown
  ASoC: tas2562: Fix sample rate error message
  ASoC: Intel: Skylake: Fix available clock counter incrementation
  ASoC: soc-pcm/soc-compress: don't use snd_soc_dapm_stream_stop()
  ASoC: meson: g12a: add tohdmitx reset
  ASoC: pcm512x: Fix unbalanced regulator enable call in probe error path
  ASoC: soc-core: fix for_rtd_codec_dai_rollback() macro
  ASoC: topology: Fix memleak in soc_tplg_manifest_load()
  ASoC: topology: Fix memleak in soc_tplg_link_elems_load()
  ...

Mark mips_ejtag_fdc_encode() methods switch-case-4 as expecting to
fall through.

This patch fixes the following warning:

drivers/tty/mips_ejtag_fdc.c: In function ‘mips_ejtag_fdc_encode’:
drivers/tty/mips_ejtag_fdc.c:245:13: warning: this statement may fall through [-Wimplicit-fallthrough=]
   word.word &= 0x00ffffff;
   ~~~~~~~~~~^~~~~~~~~~~~~
drivers/tty/mips_ejtag_fdc.c:246:2: note: here
  case 3:
  ^~~~
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Link: https://lore.kernel.org/r/20200306124913.151A68030792@mail.baikalelectronics.ruSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Many embedded boards have a disconnected TTL level serial which can
generate some garbage that can lead to spurious false sysrq detects.

Currently, sysrq can be either completely disabled for serial console
or always disabled (with CONFIG_MAGIC_SYSRQ_SERIAL), since
commit 732dbf3a ("serial: do not accept sysrq characters via serial port")

At Arista, we have such boards that can generate BREAK and random
garbage. While disabling sysrq for serial console would solve
the problem with spurious false sysrq triggers, it's also desirable
to have a way to enable sysrq back.

As a measure of balance between on and off options, add
MAGIC_SYSRQ_SERIAL_SEQUENCE which is a string sequence that can enable
sysrq if it follows BREAK on a serial line. The longer the string - the
less likely it may be in the garbage.

Having the way to enable sysrq was beneficial to debug lockups with
a manual investigation in field and on the other side preventing false
sysrq detections.
Based-on-patch-by: Vasiliy Khoruzhick <vasilykh@arista.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200302175135.269397-3-dima@arista.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Many embedded boards have a disconnected TTL level serial which can
generate some garbage that can lead to spurious false sysrq detects.

Currently, sysrq can be either completely disabled for serial console
or always disabled (with CONFIG_MAGIC_SYSRQ_SERIAL), since
commit 732dbf3a ("serial: do not accept sysrq characters via serial port")

At Arista, we have such boards that can generate BREAK and random
garbage. While disabling sysrq for serial console would solve
the problem with spurious false sysrq triggers, it's also desirable
to have a way to enable sysrq back.

Having the way to enable sysrq was beneficial to debug lockups with
a manual investigation in field and on the other side preventing false
sysrq detections.

As a preparation to add sysrq_toggle_support() call into uart,
remove a private copy of sysrq_enabled from sysctl - it should reflect
the actual status of sysrq.

Furthermore, the private copy isn't correct already in case
sysrq_always_enabled is true. So, remove __sysrq_enabled and use a
getter-helper sysrq_mask() to check sysrq_key_op enabled status.

Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200302175135.269397-2-dima@arista.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit e490c914 ("tty: Add software emulated RS485 support for 8250")
introduced support to use RTS as an rs485 Transmit Enable signal if data
is transmitted through the tty layer.

Console messages bypass the tty layer and instead are emitted via
serial8250_console_write().  Amend that function to drive RTS as well,
allowing for a console on rs485 ports.

Note that serial8250_console_write() may be called concurrently to the
tty layer accessing the port.  The two protect their accesses with the
port lock, but serial8250_console_write() may find RTS still being
asserted by the tty layer, in which case it shouldn't be deasserted
after the console message has been printed.  Recognize such situations
by checking the em485->tx_stopped flag.

If a delay_rts_before_send or delay_rts_after_send has been specified,
serial8250_console_write() busy-waits for its duration.  Optimizations
for those wait times are conceivable:  E.g. if RTS is already asserted,
we could check whether em485->start_tx_timer is active and wait only
for the remaining expire time.  But this would require calling into
the hrtimer infrastructure, which involves acquiring locks and
potentially reprogramming timer hardware.  Such operations seem too
risky in the context of console printout, which needs to work even when
the kernel has crashed and emits a BUG splat.  So I've gone with a
simplistic solution which just always waits for the full delay.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Matwey V. Kornilov <matwey@sai.msu.ru>
Link: https://lore.kernel.org/r/65edffce4670a19e598015c03cbe46f1ffd93e43.1582895077.git.lukas@wunner.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Amend 8250_bcm2835aux.c to support rs485 as introduced for 8250_omap.c
by commit e490c914 ("tty: Add software emulated RS485 support for
8250").

The bcm2835aux differs from omap chips by inverting the meaning of RTS
in the MCR register:  If the bit is clear, RTS is high.  With omap, it's
apparently the other way round.

Moreover, omap achieves half-duplex mode by disabling the UART_IER_RDI
interrupt and clearing the RX FIFO when TX stops.  This approach doesn't
work on bcm2835aux because the UART_LSR_DR bit is set even when
UART_IER_RDI is disabled.  Consequently, serial8250_handle_irq() invokes
serial8250_rx_chars() to empty the FIFO and characters are received even
though the user requested half-duplex.  Solve by disabling the receiver
using the non-standard CNTL register.

Cache that register in the driver's private data for performance.  Set
the private data pointer before calling serial8250_register_8250_port()
to prevent a null pointer deref in case one of the rs485 callbacks is
invoked immediately after port registration.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Matwey V. Kornilov <matwey@sai.msu.ru>
Link: https://lore.kernel.org/r/dd86460e20a8f979b7272a0bde73640312b902b1.1582895077.git.lukas@wunner.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit e490c914 ("tty: Add software emulated RS485 support for 8250")
introduced support to use RTS as an rs485 Transmit Enable signal.
So far the only drivers taking advantage of it are 8250_omap.c and
8250_of.c.

We're about to make use of the feature in 8250_bcm2835aux.c as well.
The bcm2835aux differs from omap chips by inverting the meaning of RTS
in the MCR register.  Moreover, omap achieves half-duplex mode by
disabling the RX interrupt and clearing the RX FIFO when TX stops.
The bcm2835aux requires disabling the receiver instead.

Support these behavioral differences by generalizing the rs485 emulation:
Introduce ->rs485_start_tx() and ->rs485_stop_tx() callbacks in struct
uart_8250_port, provide generic implementations containing the existing
code and use them as callbacks in 8250_omap.c and 8250_of.c.

start_tx_rs485() is idempotent in that it recognizes whether RTS is
already asserted.  Achieve the same by introducing a tx_stopped flag in
struct uart_8250_em485.  This may even perform a little better on arches
where memory access is faster than mmio access.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Matwey V. Kornilov <matwey@sai.msu.ru>
Link: https://lore.kernel.org/r/5ac0464ae4414708e723a1e0d52b0c1b2bd41b9b.1582895077.git.lukas@wunner.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

When rs485 transmission over an 8250 port stops, __stop_tx() assigns
active_timer = NULL before calling __stop_tx_rs485().

That function in turn either assigns active_timer = stop_tx_timer and
rearms the timer (in case a delay_rts_after_send needs to be observed)
or directly calls __do_stop_tx_rs485().

Move the assignment active_timer = NULL to __stop_tx_rs485() into the
branch which directly calls __do_stop_tx_rs485(), thereby avoiding a
duplicate assignment and simplifying the code.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Matwey V. Kornilov <matwey@sai.msu.ru>
Link: https://lore.kernel.org/r/bca638405550eaf92f0c6060b553b687f35885e0.1582895077.git.lukas@wunner.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Amend the generic ->rs485_config() callback to sanitize RTS polarity and
zero-fill the padding (in addition to the existing sanitization of the
RTS delays).
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Matwey V. Kornilov <matwey@sai.msu.ru>
Link: https://lore.kernel.org/r/ff833721bc372d38678f289eb2a44dbf016d5203.1582895077.git.lukas@wunner.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit e490c914 ("tty: Add software emulated RS485 support for 8250")
introduced support to use RTS as an rs485 Transmit Enable signal.
Drivers opt in to the feature by calling serial8250_em485_init() from
their ->rs485_config() callback.

So far there are two drivers doing that, 8250_omap.c and 8250_of.c.
Both use an identical callback.  We're about to add a third user of that
callback, therefore deduplicate it and move it to 8250_port.c.

Drivers now opt in to rs485 software emulation by assigning the generic
serial8250_rs485_config() callback introduced herein to their
.rs485_config struct member.  This change allows unexporting
serial8250_em485_init() and declaring it static.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Matwey V. Kornilov <matwey@sai.msu.ru>
Cc: Heiko Schocher <hs@denx.de>
Link: https://lore.kernel.org/r/fcef63642dc4eae41ae7842d23747b2bf5d40285.1582895077.git.lukas@wunner.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Retrieve rs485 devicetree properties on registration of 8250 ports in
case they are attached to an rs485 transceiver.

If the property "linux,rs485-enabled-at-boot-time" is present, invoke
the ->rs485_config() callback to immediately deassert RTS, thereby
ceasing control of the bus.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Giulio Benetti <giulio.benetti@micronovasrl.com>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/5908ea89b7f9da54872d6634b606d83db032297a.1582895077.git.lukas@wunner.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

serial8250_do_set_mctrl() currently allows modifying the RTS modem
control line even when RTS is used as an rs485 Transmit Enable signal.
It is thus possible for user space to interfere with rs485 communication
by invoking a TIOCMSET ioctl().

Ignore such change requests and retain the current RTS polarity when in
rs485 mode.  Note that serial8250_set_mctrl() is always called with
port->lock held, so there's no risk that RTS is changed concurrently.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Matwey V. Kornilov <matwey@sai.msu.ru>
Link: https://lore.kernel.org/r/b1ce34ca9bc4d7bdc6e9852fcf30b1f4e37c8a80.1582895077.git.lukas@wunner.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

If a driver exposes early consoles with EARLYCON_DECLARE() and
OF_EARLYCON_DECLARE(), pefer the non-OF variant if the user specifies it
by
  earlycon=<driver>,<options>

The rationale behind this is that some drivers register multiple setup
functions under the same driver name. Eg.

OF_EARLYCON_DECLARE(lpuart, "fsl,vf610-lpuart", lpuart_early_console_setup);
OF_EARLYCON_DECLARE(lpuart32, "fsl,ls1021a-lpuart", lpuart32_early_console_setup);
OF_EARLYCON_DECLARE(lpuart32, "fsl,imx7ulp-lpuart", lpuart32_imx_early_console_setup);
EARLYCON_DECLARE(lpuart, lpuart_early_console_setup);
EARLYCON_DECLARE(lpuart32, lpuart32_early_console_setup);

It depends on the order of the entries which console_setup() actually
gets called. To make things worse, I guess it also depends on the
compiler how these are ordered. Thus always prefer the EARLYCON_DECLARE()
ones.
Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20200220174607.24285-1-michael@walle.ccSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>