Avoid usb reset crashes by making tty_io cdevs truly dynamic
Signed-off-by: NRichard Watts <rrw@kynesim.co.uk>
Reported-by: NDuncan Mackintosh <DMackintosh@cbnl.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This reverts commit e95044ba.

Commit e95044ba ("tty: serial: imx.c: Reset UART before activating
interrupts") terribly messes up with the console on mx6 boards, so
let's revert it.
Reported-by: Nkernelci.org bot <bot@kernelci.org>
Cc: David Jander <david@protonic.nl>
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Opens of /dev/ptmx don't use tty_open() so debug messages are
not printed for those opens; print a debug message with the
open count (which must always be 1) if TTY_DEBUG_HANGUP is defined.

NB: Each tty core source file undefs support for debug messages.
The relevant source file must be patched/edited to enable these
messages.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add debug messages for ldisc open and close, and remove
"closing ldisc" message from tty_ldisc_release(), because a
close message is now printed for both ldiscs; always print ldisc
pointer first so ldisc changes are easier to identify.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add tty_debug_wait_until_sent() macro which uses tty_debug() to print
the debug message; remove inlined #ifdef.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Replace tty_ldisc_debug() macro definition; substitute with equivalent
tty_debug() invocation.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add tty_debug_hangup() macro which uses tty_debug to print the
debug message; remove inlined #ifdefs.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Introduce tty_debug() macro to output uniform debug information for
tty core debug messages (function name and tty name).

Note: printk(KERN_DEBUG) is retained here over pr_debug() since
messages can be enabled in non-DEBUG builds.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Output the function name, tty name, and invariant failure (if applicable).
Add the tty count to the tty_open() message. Fix the disassociate_ctty()
message, which printed the NULL pointer and the wrong message.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The Kconfig for this driver is currently:

config SERIAL_SUNHV
        bool "Sun4v Hypervisor Console support"

...meaning that it currently is not being built as a module by
anyone.  Lets remove the modular and unused code here, so that
when reading the driver there is no doubt it is builtin-only.

Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.

We don't swap module.h for init.h since this file has init.h already.

We leave some tags like MODULE_LICENSE for documentation purposes, and
for the "git blame" value.  Also note that MODULE_DEVICE_TABLE is a
no-op for non-modular code, so we remove that too.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: sparclinux@vger.kernel.org
Cc: linux-serial@vger.kernel.org
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The Kconfig for this driver is currently:

config SERIAL_SUNCORE
        bool

...meaning that it currently is not being built as a module by
anyone.  Lets remove the modular and unused code here, so that
when reading the driver there is no doubt it is builtin-only.

Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.

We don't swap module.h for init.h since this file has init.h already.

We leave some tags like MODULE_LICENSE for documentation purposes, and
for the "git blame" value.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: sparclinux@vger.kernel.org
Cc: linux-serial@vger.kernel.org
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The Kconfig for this option is currently:

config SERIAL_LANTIQ
    bool "Lantiq serial driver"

...meaning that it currently is not being built as a module by anyone.
Lets remove the couple traces of modularity, so that when reading the
driver there is no doubt it is builtin-only.

Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.

We delete the MODULE_DESCRIPTION and LICENSE tags since they are
not adding any new information above and beyond what is at the top
of the file.  Also note that MODULE_DEVICE_TABLE is a no-op for
non-modular code, so we remove that as well.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: linux-serial@vger.kernel.org
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The Kconfig for this option is currently:

config SERIAL_SGI_L1_CONSOLE
    bool "SGI Altix L1 serial console support"

...meaning that it currently is not being built as a module by anyone.
Lets remove the orphaned module code, so that when reading the
driver there is no doubt it is builtin-only.  We could consider
making it tristate, but the above bool has been there since before
the start of git history, which isn't all that surprising, since
consoles are typically critical to have at early boot.  So adding
tristate is really of no value here.

Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: linux-serial@vger.kernel.org
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit 84f57d9e ("tty: serial/samsung: fix modular build") fixed
build issues when the driver was built as a module. One of those was
that printascii is only accessible when the driver is built-in.

But there is no need to check for defined(CONFIG_DEBUG_LL) since the
SERIAL_SAMSUNG_DEBUG Kconfig symbol already depends on DEBUG_LL.
Signed-off-by: NJavier Martinez Canillas <javier@osg.samsung.com>
Reviewed-by: NKrzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: NKukjin Kim <kgene@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The advance of the 'read' buffer index belongs in the outer
flip buffer consume loop, with the other buffer index arithmetic.

No functional change.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Clarify flip buffer producer/consumer operation; the use of
smp_load_acquire() and smp_store_release() more clearly indicates
which memory access requires a barrier.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Pasting text with gpm on a VC produced warning [1]. Reset task state
to TASK_RUNNING in the paste_selection() loop, if the loop did not
sleep.

[1]
WARNING: CPU: 6 PID: 1960 at /home/peter/src/kernels/mainline/kernel/sched/core.c:7286 __might_sleep+0x7f/0x90()
do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffff8151805e>] paste_selection+0x9e/0x1a0
Modules linked in: btrfs xor raid6_pq ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs libcrc32c .....
CPU: 6 PID: 1960 Comm: gpm Not tainted 4.1.0-rc7+tty-xeon+debug #rc7+tty
Hardware name: Dell Inc. Precision WorkStation T5400  /0RW203, BIOS A11 04/30/2012
 ffffffff81c9c0a0 ffff8802b0fd3ac8 ffffffff8185778a 0000000000000001
 ffff8802b0fd3b18 ffff8802b0fd3b08 ffffffff8108039a ffffffff82ae8510
 ffffffff81c9ce00 0000000000000015 0000000000000000 0000000000000000
Call Trace:
 [<ffffffff8185778a>] dump_stack+0x4f/0x7b
 [<ffffffff8108039a>] warn_slowpath_common+0x8a/0xc0
 [<ffffffff81080416>] warn_slowpath_fmt+0x46/0x50
 [<ffffffff810ddced>] ? __lock_acquire+0xe2d/0x13a0
 [<ffffffff8151805e>] ? paste_selection+0x9e/0x1a0
 [<ffffffff8151805e>] ? paste_selection+0x9e/0x1a0
 [<ffffffff810ad4ff>] __might_sleep+0x7f/0x90
 [<ffffffff8185f76a>] down_read+0x2a/0xa0
 [<ffffffff810bb1d8>] ? sched_clock_cpu+0xb8/0xe0
 [<ffffffff8150d1dc>] n_tty_receive_buf_common+0x4c/0xba0
 [<ffffffff810dc875>] ? mark_held_locks+0x75/0xa0
 [<ffffffff81861c95>] ? _raw_spin_unlock_irqrestore+0x65/0x80
 [<ffffffff810b49a1>] ? get_parent_ip+0x11/0x50
 [<ffffffff8150dd44>] n_tty_receive_buf2+0x14/0x20
 [<ffffffff81518117>] paste_selection+0x157/0x1a0
 [<ffffffff810b77b0>] ? wake_up_state+0x20/0x20
 [<ffffffff815203f8>] tioclinux+0xb8/0x2c0
 [<ffffffff81515bfe>] vt_ioctl+0xaee/0x11a0
 [<ffffffff810baf75>] ? sched_clock_local+0x25/0x90
 [<ffffffff810bbe11>] ? vtime_account_user+0x91/0xa0
 [<ffffffff8150810c>] tty_ioctl+0x20c/0xe20
 [<ffffffff810bbe11>] ? vtime_account_user+0x91/0xa0
 [<ffffffff810b49a1>] ? get_parent_ip+0x11/0x50
 [<ffffffff810b4a69>] ? preempt_count_sub+0x49/0x50
 [<ffffffff811ab71c>] ? context_tracking_exit+0x5c/0x290
 [<ffffffff811ab71c>] ? context_tracking_exit+0x5c/0x290
 [<ffffffff81248b98>] do_vfs_ioctl+0x318/0x570
 [<ffffffff810dca8d>] ? trace_hardirqs_on+0xd/0x10
 [<ffffffff810dc9b5>] ? trace_hardirqs_on_caller+0x115/0x1e0
 [<ffffffff81254acc>] ? __fget_light+0x6c/0xa0
 [<ffffffff81248e71>] SyS_ioctl+0x81/0xa0
 [<ffffffff81862832>] system_call_fastpath+0x16/0x7a
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

While closing, new rx data may be received after the input buffers
have been flushed but before stop_rx() halts receiving [1]. The
new data might not be processed by flush_to_ldisc() until after
uart_shutdown() and normal input processing is re-enabled (ie.,
tty->closing = 0). The race is outlined below:

CPU 0                         | CPU 1
                              |
uart_close()                  |
   tty_port_close_start()     |
      tty->closing = 1        |
      tty_ldisc_flush()       |
                              | => IRQ
                              |   while (LSR & data ready)
                              |      uart_insert_char()
                              |   tty_flip_buffer_push()
                              | <= EOI
   stop_rx()                  |   .
   uart_shutdown()            |   .
      free xmit.buf           |   .
   tty_port_tty_set(NULL)     |   .
   tty->closing = 0           |   .
                              | flush_to_ldisc()
                              |   n_tty_receive_buf_common()
                              |      __receive_buf()
                              |         ...
                              |         commit_echoes()
                              |            uart_flush_chars()
                              |               __uart_start()
                              | ** OOPS on port.tty deref **
   tty_ldisc_flush()          |

Input processing must be prevented from echoing (tty->closing = 1)
until _after_ the input buffers have been flushed again at the end
of uart_close().

[1] In fact, some input may actually be buffered _after_ stop_rx()
since the rx interrupt may have already triggered but not yet been
handled when stop_rx() disables rx interrupts.

Fixes: 2e758910 ("serial: core: Flush ldisc after dropping port
mutex in uart_close()")
Reported-by: NRobert Elliott <elliott@hp.com>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The maximum bitrate supported depends on the clock rate used in BRG.
This is stored in port.uartclk during probe. Respecting the 16x
oversampling higher bitrates can be supported.
Signed-off-by: NAlexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

i2c_driver does not need to set an owner because i2c_register_driver()
will set it.
Signed-off-by: NKrzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

platform_driver does not need to set an owner because
platform_driver_register() will set it.
Signed-off-by: NKrzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

For now this improvement is only used with TX DMA transfers. The data
width must be set properly when configuring the DMA controller. Also
the FIFO configuration must be set to match the DMA transfer data
width:
TXRDYM (Transmitter Ready Mode) and RXRDYM (Receiver Ready Mode) must
be set into the FIFO Mode Register. These values are used by the
USART to trigger the DMA controller. In single data mode they are not
used and should be reset to 0.
So the TXRDYM bits are changed to FOUR_DATA; then USART triggers the
DMA controller when at least 4 data can be written into the TX FIFO
througth the THR. On the other hand the RXRDYM bits are left unchanged
to ONE_DATA.

Atmel eXtended DMA controller allows us to set a different data width
for each part of a scatter-gather transfer. So when calling
dmaengine_slave_config() to configure the TX path, we just need to set
dst_addr_width to the maximum data width. Then DMA writes into THR are
split into up to two parts. The first part carries the first data to
be sent and has a length equal to the greatest multiple of 4 (bytes)
lower than or equal to the total length of the TX DMA transfer. The
second part carries the trailing data (up to 3 bytes). The first part
is written by the DMA into THR using 32 bit accesses, whereas 8bit
accesses are used for the second part.
Signed-off-by: NCyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: NNicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Depending on the hardware, TX and RX FIFOs may be available. The RX
FIFO can avoid receive overruns, especially when DMA transfers are
not used to read data from the Receive Holding Register. For heavy
system load, The CPU is likely not be able to fetch data fast enough
from the RHR.

In addition, the RX FIFO can supersede the DMA/PDC to control the RTS
line when the Hardware Handshaking mode is enabled. Two thresholds
are to be set for that purpose:
- When the number of data in the RX FIFO crosses and becomes lower
  than or equal to the low threshold, the RTS line is set to low
  level: the remote peer is requested to send data.
- When the number of data in the RX FIFO crosses and becomes greater
  than or equal to the high threshold, the RTS line is set to high
  level: the remote peer should stop sending new data.
- low threshold <= high threshold
Once these two thresholds are set properly, this new feature is
enabled by setting the FIFO RTS Control bit of the FIFO Mode Register.

FIFOs also introduce a new multiple data mode: the USART works either
in multiple data mode or in single data (legacy) mode.

If MODE9 bit is set into the Mode Register or if USMODE is set to
either LIN_MASTER, LIN_SLAVE or LON_MODE, FIFOs operate in single
data mode. Otherwise, they operate in multiple data mode.

In this new multiple data mode, accesses to the Receive Holding
Register or Transmit Holding Register slightly change.

Since this driver implements neither the 9bit data feature (MODE9 bit
set into the Mode Register) nor LIN modes, the USART works in
multiple data mode whenever FIFOs are available and enabled. We also
assume that data are 8bit wide.

In single data mode, 32bit access CAN be used to read a single data
from RHR or write a single data into THR.
However in multiple data mode, a 32bit access to RHR now allows us to
read four consecutive data from RX FIFO. Also a 32bit access to THR
now allows to write four consecutive data into TX FIFO. So we MUST
use 8bit access whenever only one data have to be read/written at a
time.
Signed-off-by: NCyrille Pitchen <cyrille.pitchen@atmel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This patch replaces the UART_PUT_*, resp. UART_GET_*, macros by
atmel_uart_writel(), resp. atmel_uart_readl(), inline function calls.
Signed-off-by: NCyrille Pitchen <cyrille.pitchen@atmel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

task_pgrp requires an rcu or tasklist lock to be obtained if the returned pid
is to be dereferenced, which kill_pgrp does. Obtain an RCU lock for the
duration of use.
Signed-off-by: NPatrick Donnelly <batrick@batbytes.com>
Reviewed-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The XR17V35X UART needs the ECB bit set in its XR_EFR
register to enable access to IER [7:5], ISR [5:4], FCR[5:4],
MCR[7:5], and MSR [7:0].

Also reset the IER register to mask interrupts after access
to all bits of this register has been enabled.

This makes my 8-port XR17V35X working with the in-kernel
serial driver.

Cc: Joe Schultz <jschultz@xes-inc.com>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>
Reviewed-by: NPeter Hurley <peter@hurleysoftware.com>
Reviewed-by: NMichael Welling <mwelling@ieee.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

An already-active sender can swamp the interrupt handler with
"too much work" if the rx interrupts are enabled when the fifo is
disabled and operating in single-byte mode.

Defer rx and line status interrupt enable until after the fifos
are enabled in set_termios(), but at least initialize the shadow
IER value with the interrupts which will be enabled.
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit ed71871b ("tty/8250_early: Turn serial_in/serial_out into
weak symbols") made these routines weak to allow platform specific
Big endian override

However recent updates to core, specifically ebc5e200 ("serial:
of_serial: Support big-endian register accesses") and 6e63be3f
("serial: earlycon: Add support for big-endian MMIO accesses") means
that round about way to overide the early serial accessors is no longer
needed.

Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Kevin Cernekee <cernekee@gmail.com>
Acked-by: NNoam Camus <noamc@ezchip.com>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Reviewed-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Refactor base port operations into new file; 8250_port.c.

Legacy irq handling, RSA port support, port storage for universal
driver, driver definition, module parameters and linkage remain in
8250_core.c

The source file split and resulting modules is diagrammed below:

  8250_core.c ====>   8250_core.c __
              \                     \
               \                     +-- 8250.ko (alias 8250_core)
                \     8250_pnp.c  __/     (universal driver)
                 \
                  =>  8250_port.c __
                                    \
                                     +-- 8250_base.ko
                      8250_dma.c  __/     (port operations)
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This reverts commit 068500e0.

According to some tests, SDMA support is broken at least for i.MX6 without
HW flow control. Different forms of data-corruption appear either with
the ROM firmware for the SDMA controller as well as when loading Freescale
provided SDMA firmware versions 1.1 or 3.1.
Signed-off-by: NDavid Jander <david@protonic.nl>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

If the UART has been in use before this driver was loaded, IRQs might be
active and get fired as soon as we set the handler, which will crash
in the spin_lock_irqsave(&sport->port.lock, flags) because port.lock is
not initialized until the port is added at the end of probe.
Signed-off-by: NDavid Jander <david@protonic.nl>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

To prevent problems with interrupt latency, and due to the fact, that
the error will be counted anyway (icount.overrun), the dev_err is simply
removed.

Background:
If an rx-fifo overflow occurs a dev_err message was called in interrupt
context. Since dev_err messages are written to console in a synchronous way
(unbuffered), and console may be a serial terminal, this leads to a
highly increased interrupt-latency (several milliseconds).
As a result of the high latency more rx-fifo overflows will happen, and
therefore a feedback loop of errors is created.
Signed-off-by: NManfred Schlaegl <manfred.schlaegl@gmx.at>
Acked-By: NAlexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As can be seen in function uart_insert_char (serial_core) the element
buf_overrun of struct uart_icount is used to count overruns of
tty-buffer.
Added support for counting of overruns in imx driver analogue to
serial_core.
Signed-off-by: NManfred Schlaegl <manfred.schlaegl@gmx.at>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Disable interrupts before requesting them in order to fix a kernel oops
after lauching a kernel via kexec.

Tested on a imx6sl-evk board.
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Being a soft core, it can be located not only on PPC or Microblaze
platforms.

Since the driver already does endianness detection we only need to
change the Kconfig to use it in other arches.

This is also done in other softcores as xilinx-spi.
Signed-off-by: NRicardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

SysRq support activation depends on CONFIG_SERIAL_STM32_USART_CONSOLE, but
this config flag does not exists.

This patch fix this by depending on the valid config flag, which is
SERIAL_STM32_CONSOLE.
Reported-by: NAndreas Ruprecht <andreas.ruprecht@fau.de>
Signed-off-by: NMaxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Calls to regmap_raw_read/write needed register rewrite in a
similar way as function calls to regmap_read/write already had.
This enables reading/writing the serial datastream to the device.
Signed-off-by: NBo Svangård <bo.svangard@embeddedart.se>
Signed-off-by: NJakub Kicinski <kubakici@wp.pl>
Signed-off-by: NJon Ringle <jringle@gridpoint.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

When I2C=m and SPI=y or-ing them will produce =y while
what we need is the lower bound, i.e. =m.  Fortunately
SPI is a boolean so we need to handle only one special
case.
Reported-by: Nkbuild test robot <fengguang.wu@intel.com>
Signed-off-by: NJakub Kicinski <kubakici@wp.pl>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

While UART work in DMA mode, function start_rx will request descriptor
from DMA engine, if there is no left descriptor UART, driver will give
err logs "DMA slave single fail".

currently start_rx is called in set_termios function, so everytime, port
setting will call start_rx once.

Now put start_rx in startup, it will be called once while open the port.
Signed-off-by: NQipan Li <Qipan.Li@csr.com>
Signed-off-by: NBarry Song <Baohua.Song@csr.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

when UART works in DMA mode and left bytes in rx fifo less than
a dma transfer unit, DMA engine can't transfer the bytes out
to rx DMA buffer. so it need a way to fetch them out and
flush them into tty buffer in time.

in the above case, we want UART switch from DMA mode to PIO mode and
fetch && flush bytes into tty layer buffer until rxfifo become empty,
after that done let UART switch from PIO mode back to DMA mode.
(record as method1)

method1 result in the next receive result wrong. for example in PIO part
of method1, we fetched && pushed X1...X3 bytes, when UART rxfifo newly
received Y1...Y4 bytes, UART trigger a DMA unit transfer, the DMA unit's
content is X1...X3Y1 and rxfifo fifo status is empty, so X1X2X3 pushed
twice by PIO way and DMA way also the bytes Y2Y3Y4 missed. add rxfifo
reset operation before UART switch back to DMA mode would resolve the
issue. ([method1 + do fifo reset] record as method2)

before the commit, UART driver use method2. but methd2 have a risk of
data loss, as if UART's shift register receive a complete byte and
transfer it into rxfifo before rxfifo reset operation the byte will
loss.

UART and USP have the similar bits CLEAR_RX_ADDR_EN(uart)/FRADDR_CLR_EN(usp),
When found UART controller changing I/O to DMA mode, UART controller
clears the two low bits of read point (rx_fifo_addr[1:0]).
when enable the bit + method1(record as method3), in above example
the DMA unit's content is X1...X3Y1 and there are Y2Y3Y4 in rxfifo by
experiment, we just push bytes in rx DMA buffer.

BTW, the workaround works only for UART receive DMA channel use SINGLE
DMA mode.
Signed-off-by: NQipan Li <Qipan.Li@csr.com>
Signed-off-by: NBarry Song <Baohua.Song@csr.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>