Currently the pl011_probe() function is relying on some AMBA IDs
and a device tree node to initialize the driver and a port.
Both features are not necessarily required for the driver:
- we lack AMBA IDs in the ARM SBSA generic UART and
- we lack a DT node in ACPI systems.
So lets refactor the function to ease later reuse.
Signed-off-by: NAndre Przywara <andre.przywara@arm.com>
Tested-by: NMark Langsdorf <mlangsdo@redhat.com>
Tested-by: NNaresh Bhat <nbhat@cavium.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Split the pl011_set_termios() function into smaller chunks to allow
easier reuse later when adding SBSA support.
Signed-off-by: NAndre Przywara <andre.przywara@arm.com>
Tested-by: NMark Langsdorf <mlangsdo@redhat.com>
Tested-by: NNaresh Bhat <nbhat@cavium.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Split the pl011_shutdown() function into smaller chunks to allow
easier reuse later when adding SBSA support.
Signed-off-by: NAndre Przywara <andre.przywara@arm.com>
Tested-by: NMark Langsdorf <mlangsdo@redhat.com>
Tested-by: NNaresh Bhat <nbhat@cavium.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Split the pl011_startup() function into smaller chunks to allow
easier reuse later when adding SBSA support.
Signed-off-by: NAndre Przywara <andre.przywara@arm.com>
Tested-by: NMark Langsdorf <mlangsdo@redhat.com>
Tested-by: NNaresh Bhat <nbhat@cavium.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Although we care about not unregistering the driver if there are
still ports connected during the .remove callback, we do miss this
check in the pl011_probe function. So if the current port allocation
fails, but there are other ports already registered, we will kill
those.
So factor out the port removal into a separate function and use that
in the probe function, too.
Signed-off-by: NAndre Przywara <andre.przywara@arm.com>
Tested-by: NMark Langsdorf <mlangsdo@redhat.com>
Tested-by: NNaresh Bhat <nbhat@cavium.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

In commit 02730d3c
(Merge 4.1-rc4 into tty-next), git mismerged some lines,
reintroducing a reference to the removed field
uart_amba_port.tx_irq_seen.  This causes a build failure.

This patch removes the mismerged lines, restoring the code to what
was in tty-next (which was the intention).
Signed-off-by: NDave Martin <Dave.Martin@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This reverts commit f2ee6dfa.

Jakub Kiciński observed that this patch can cause the pl011
driver to hang if if the only process with a pl011 port open is
killed by a signal, pl011_shutdown() can get called with an
arbitrary amount of data still in the FIFO.

Calling _shutdown() with the TX FIFO non-empty is questionable
behaviour and my itself be a bug.

Since the affected patch was speculative anyway, and brings limited
benefit, the simplest course is to remove the assumption that TXIS
will always be left asserted after the port is shut down.
Signed-off-by: NDave Martin <Dave.Martin@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit 734745ca serial/amba-pl011: Activate TX IRQ passively
adds some complexity and overhead in the form of a softirq
mechanism for transmitting in the absence of interrupts.

This patch simplifies the code flow to reduce the reliance on
subtle behaviour and avoid fragility under future maintenance.

To this end, the TX softirq mechanism is removed and instead
pl011_start_tx() will now simply stuff the FIFO until full
(guaranteeing future TX IRQs), or until there are no more chars
to write (in which case we don't care whether an IRQ happens).
Signed-off-by: NDave Martin <Dave.Martin@arm.com>
Signed-off-by: NJakub Kicinski <kubakici@wp.pl>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This reverts commit f2ee6dfa.

Jakub Kiciński observed that this patch can cause the pl011
driver to hang if if the only process with a pl011 port open is
killed by a signal, pl011_shutdown() can get called with an
arbitrary amount of data still in the FIFO.

Calling _shutdown() with the TX FIFO non-empty is questionable
behaviour and my itself be a bug.

Since the affected patch was speculative anyway, and brings limited
benefit, the simplest course is to remove the assumption that TXIS
will always be left asserted after the port is shut down.
Signed-off-by: NDave Martin <Dave.Martin@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Unacceptable levels of debug info will happen when the DMA driver defined in
the DT/ACPI is a blacklisted module.

Another cause for log polution would be the defer probing of the DMA driver
taking too long - in which case the message that this commit removes would be
cluttering the logs due to the init daemons activity.
Signed-off-by: NJorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Fix a race condition that happens when device_initcall(pl011_dma_initicall)
is executed before all the devices have been probed - this issue was observed on
a hisi_6220 SoC (HiKey board from Linaro).

The deferred driver probing framework relies on late_initcall to trigger
deferred probes so it is just possible that, even with a valid DMA driver ready
to be loaded, we fail to synchronize with it.

The proposed implementation delays probing the DMA until dma_startup.

As this is invoked on port startup and port resume - but DMA probing is only
required once - we avoid calling multiple times using a new field in
uart_amba_port to track this scenario.

This commit allows for subsequent attempts to associate an external DMA if the
DMA driver itself is not available (but present in the deferred probe pending
list).
Signed-off-by: NJorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Getting the TX IRQ re-asserted from scratch can be inefficient in
some setups.

This patch avoids clearing the TX IRQ across pl011_shutdown()...
pl011_startup(), so that if the port is closed and reopened, the
IRQ will still work afterwards without having to bootstrap it again.

The TX IRQ continues to be masked in IMSC when the UART is not in
use.
Signed-off-by: NDave Martin <Dave.Martin@arm.com>
Tested-by: NAndre Przywara <andre.przywara@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The current PL011 driver transmits a dummy character when the UART
is opened, to assert the TX IRQ for the first time
(see pl011_startup()).  The UART is put in loopback mode temporarily,
so the receiver presumably shouldn't see anything.

However...

At least some platforms containing a PL011 send characters down the
wire even when loopback mode is enabled.  This means that a
spurious NUL character may be seen at the receiver when the PL011 is
opened through the TTY layer.

The current code also temporarily sets the baud rate to maximum and
the character width to the minimum, to that the dummy TX completes
as quickly as possible.  If this is seen by the receiver it will
result in a framing error and can knock the receiver out of sync --
turning subsequent output into garbage until synchronisation
is reestablished.  (Particularly problematic during boot with systemd.)

To avoid spurious transmissions, this patch removes assumptions about
whether the TX IRQ will fire until at least one TX IRQ has been seen.

Instead, the UART will unmask the TX IRQ and then slow-start via
polling and timer-based soft IRQs initially.  If the TTY layer writes
enough data to fill the FIFO to the interrupt threshold in one go,
the TX IRQ should assert, at which point the driver changes to
fully interrupt-driven TX.

In this way, the TX IRQ is activated as a side-effect instead of
being done deliberately.

This should also mean that the driver works on the SBSA Generic
UART[1] (a cut-down PL011) without invasive changes.  The Generic
UART lacks some features needed for the dummy TX approach to work
(FIFO disabling and loopback).

[1] Server Base System Architecture (ARM-DEN-0029-v2.3)
    http://infocenter.arm.com/
    (click-thru required :/)
Signed-off-by: NDave Martin <Dave.Martin@arm.com>
Tested-by: NAndre Przywara <andre.przywara@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add equivalent attributes to those provided in the platform data
for use when RX DMA is enabled.
Signed-off-by: NAndrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

If the DMA engine doesn't support residue processing then the RX DMA
handling won't work terribly well if polling is enabled.  So, disable
RX DMA if residue handling isn't available.
Signed-off-by: NAndrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The DMA engines on some systems require that the dma_length is set
when using scatter gather lists.
Signed-off-by: NAndrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The existing code assumed that PL011_DMA_BUFFER_SIZE == UART_XMIT_SIZE,
which may not always be the case.  This allows for these two being
different sizes and not copying too much data.
Signed-off-by: NAndrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Allocating with __GFP_DMA avoids the need for bounce buffers
Signed-off-by: NAndrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit 479e9b94 ("serial: Refactor uart_flush_buffer() from
uart_close") refactored the uart_flush_buffer() in uart_close() into
those drivers that define a flush_buffer() method. However, in the
amba-pl011 driver configured without CONFIG_DMA_ENGINE, flush_buffer()
is a NULL method, so the direct call fails to compile.

Check and call the flush_buffer() method through the ops table instead.
Reported-by: NFengguang Wu <fengguang.wu@intel.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

In the context of the final tty & port close, flushing the tx
ring buffer after the hardware has already been shutdown and
the ring buffer freed is neither required nor desirable.

uart_flush_buffer() performs 3 operations:
1. Resets tx ring buffer indices, but the tx ring buffer has
   already been freed and the indices are reset if the port is
   re-opened.
2. Calls uart driver's flush_buffer() method
   5 in-tree uart drivers define flush_buffer() methods:
     amba-pl011, atmel-serial, imx, serial-tegra, timbuart
   These have been refactored into the shutdown() method, if
   required.
3. Kicks the ldisc for more writing, but this is undesirable.
   The file handle is being released; any waiting writer will
   will be kicked out by tty_release() with a warning. Further,
   the N_TTY ldisc may generate SIGIO for a file handle which
   is no longer valid.

Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Universally adopt container_of() for all pointer conversion from
uart_port to uart_amba_port.
Signed-off-by: NDaniel Thompson <daniel.thompson@linaro.org>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: linux-serial@vger.kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The label 'out' is only used to return the error code. We can return the
error code directly and remove 'out' label.
Signed-off-by: NTushar Behera <tushar.b@samsung.com>
Reviewed-by: NDaniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

If IGNBRK is set without either BRKINT or PARMRK set, some uart
drivers send a 0x00 byte for BREAK without the TTYBREAK flag to the
line discipline, when it should send either nothing or the TTYBREAK flag
set. This happens because the read_status_mask masks out the BI
condition, which uart_insert_char() then interprets as a normal 0x00 byte.

SUS v3 is clear regarding the meaning of IGNBRK; Section 11.2.2, General
Terminal Interface - Input Modes, states:
  "If IGNBRK is set, a break condition detected on input shall be ignored;
   that is, not put on the input queue and therefore not read by any
   process."

Fix read_status_mask to include the BI bit if IGNBRK is set; the
lsr status retains the BI bit if a BREAK is recv'd, which is
subsequently ignored in uart_insert_char() when masked with the
ignore_status_mask.

Affected drivers:
8250 - all
serial_txx9
mfd
amba-pl010
amba-pl011
atmel_serial
bfin_uart
dz
ip22zilog
max310x
mxs-auart
netx-serial
pnx8xxx_uart
pxa
sb1250-duart
sccnxp
serial_ks8695
sirfsoc_uart
st-asc
vr41xx_siu
zs
sunzilog
fsl_lpuart
sunsab
ucc_uart
bcm63xx_uart
sunsu
efm32-uart
pmac_zilog
mpsc
msm_serial
m32r_sio

Unaffected drivers:
omap-serial
rp2
sa1100
imx
icom

Annotated for fixes:
altera_uart
mcf

Drivers without break detection:
21285
xilinx-uartps
altera_jtaguart
apbuart
arc-uart
clps711x
max3100
uartlite
msm_serial_hs
nwpserial
lantiq
vt8500_serial

Unknown:
samsung
mpc52xx_uart
bfin_sport_uart
cpm_uart/core

Fixes: Bugzilla #71651, '8250_core.c incorrectly handles IGNBRK flag'
Reported-by: NIvan <athlon_@mail.ru>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Enable DT based earlycon initialization for the pl011 uart.
Signed-off-by: NRob Herring <robh@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Acked-by: NGrant Likely <grant.likely@linaro.org>

Add earlycon support for the pl011 serial port. This allows enabling
the pl011 for console when early_params are processed. This is based
on the arm64 earlyprintk support and is intended to replace it.
Signed-off-by: NRob Herring <robh@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

A recent commit ef2889f7 "serial: pl011:
Move uart_register_driver call to device probe" introduced a regression,
causing the pl011 driver to Oops if more than 1 port have been probed. Fix
the Oops by only calling uart_unregister_driver() once after the last port
has been removed.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The amba-pl011.c driver sets DMA burst size equal to FIFO trigger level.
If now exactly DMA burst size bytes are received, the DMAC will retrieve
them all and no Rx timeout interrupt will be generated. To fix that set
the burst size to half the FIFO trigger level.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

uart_register_driver call binds the driver to a specific device
node through tty_register_driver call. This should typically happen
during device probe call.

In a multiplatform scenario, it is possible that multiple serial
drivers are part of the kernel. Currently the driver registration fails
if multiple serial drivers with same default major/minor numbers are
included in the kernel.

A typical case is observed with amba-pl011 and samsung-uart drivers.
Signed-off-by: NTushar Behera <tushar.behera@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

When falling back from DMA to interrupt mode the receive interrupt has to
be re-enabled to catch new incoming data.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

In pl011_rx_chars() if pl011_dma_rx_trigger_dma() succeeds it will disable
the receive interrupt, no need to do this again.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

During initialisation, a UART may already be in use for a console, so
take care to preserve things like baud rate and data format to avoid
corrupting console output.
Signed-off-by: NJon Medhurst <tixy@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The code to cope with a split tx/rx LCR_H register is non-trivial
so put it into it's own function to avoid duplication.
Signed-off-by: NJon Medhurst <tixy@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

When the pl011 is being used for a console, pl011_console_write forces
the control register (CR) to enable the UART for transmission and then
restores this to the original value afterwards. It does this while
holding the port lock.

Unfortunately, when the uart is started or shutdown - say in response to
userland using the serial device for a terminal - then this updates the
control register without any locking.

This means we can have

  pl011_console_write   Save CR
  pl011_startup         Initialise CR, e.g. enable receive
  pl011_console_write   Restore old CR with receive not enabled

this result is a serial port which doesn't respond to any input.

A similar race in reverse could happen when the device is shutdown.

We can fix these problems by taking the port lock when updating CR.
Signed-off-by: NJon Medhurst <tixy@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This reverts commit 17438217 on request
of Linus Walleij:
	Greg can you please drop or revert
	commit 17438217
	"serial: pl011: use DMA RX polling by default"
	from the TTY tree until this has been sorted out?

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Making DMA RX polling optional when DMA is on was just
over-cautious: there is one single system in the kernel tree
using this facility, Ux500 and after some testing I turned
this on also for Ux500, which means it should simply be on
by default if DMA is enabled.

Cc: Jongsung Kim <neidhard.kim@lge.com>
Cc: Chanho Min <chanho.min@lge.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Convert to modern PM ops and use the SIMPLE_DEV_PM_OPS macro to set up
the PM callbacks.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This early amba_ports declaration was introduced by commit c16d51a3 (amba
pl011: workaround for uart registers lockup) for use in the pl011_lockup_wa()
routine. This routine was later removed by commit 4fd0690b (serial: pl011:
implement workaround for CTS clear event issue).
Signed-off-by: NBaruch Siach <baruch@tkos.co.il>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Driver core clears the driver data to NULL after device_release
or on probe failure, so just remove it from here.

Driver core change:
"device-core: Ensure drvdata = NULL when no driver is bound"
(sha1: 0998d063)
Signed-off-by: NMichal Simek <michal.simek@xilinx.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Fix the following sparse warnings:

drivers/tty/serial/amba-pl011.c:687:20: warning: context imbalance in 'pl011_dma_flush_buffer' - unexpected unlock
drivers/tty/serial/amba-pl011.c:1200:13: warning: context imbalance in 'pl011_rx_chars' - unexpected unlock
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Use the wrapper function for retrieving the platform data instead of
accessing dev->platform_data directly.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>