The commit enabling DMA support even if no flow control is present
was reverted on the grounds that it uncovered a number of bugs in
the code that lead to hanging tty devices and/or missing characters.

After tracking down the issues it is clear that those were generic
bugs and had nothing to do with flow control being present or not,
only that allowing DMA without hardware flow control increased
the exposure of that code a lot.

Now that those bugs are fixed, it should be safe to re-enable DMA
support.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The reference manual states that idle condition detect should not be used
with DMA transfers, as the ROM SDMA scripts don't check those conditions.

The RAM SDMA scripts worked around this, but the change broke compatibility
with the ROM scripts.

The previous commits fixed the DMA burst sizes, so that the aging timer is
now working as described in the reference manual. With this fixed we can
remove the hack of using the idle condition detect to stop the DMA transfer
if there are no new characters incoming.

This should work with both the ROM and RAM SDMA scripts.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Triggering the DMA engine for every byte is horribly inefficient.
Also it doesn't allow to use the aging timer for the RX FIFO as this
requires the DMA engine to leave one byte remaining in the FIFO when
doing a normal burst transfer.

Adjust watermark levels so that the DMA engine can do at least 8 byte
burst transfers. This is a conservative value, as the both TX and RX
FIFOs are able to contain 32 bytes.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Simplify the DMA restart logic to always queue up the next transfer
immediately if there is at least one more byte available in the FIFO,
so that the transfer will finish in a limited time.

This way the driver stops to rely on zero length transfers to signal
transfers ends. Those will go away when the idle detect DMA requests
are disabled.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The DMA transfer is only started once we are sure it will finish
in a limited time, i.e. only after we received a RRDY interrupt.

In order to allow the watermark level to be raised the aging
timer and the corresponding interrupt need to be set up as an
additional trigger, so that the transfer is also started if the
incoming amount of bytes never reach the watermark.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This function currently doesn't use its parameter.

Change prototype to pass in watermark levels, so we can reuse this
function in the DMA setup paths. Also relocate to be near the calling
functions.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

serial8250_register_8250_port adds it to all ports it
registers. No need to set it separately.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Using the same style of declaring variables as used in the
other functions of the driver. Passing uart_port to the
function instead of uart_8250_port, as it is the one mostly
needed.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Remove the extra return.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Adding comment where the purpose of the function is
explained.

The dma parameters are not used, so removing them, and also
moving the assignment of the function to the same place
where the other dw8250_data structures members are being set
in dw8250_probe.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

If the DW_apb_uart is configured with UART_16550_COMPATIBLE
configuration parameter set, then the Busy Functionality is
not available. These UARTs will never generate the Busy
detect indication interrupt, and therefore don't need
handling for it.

This creates a small optimization for the DW_apb_uarts
configured without the busy functionality, but more
importantly, it removes the small but real risk of hitting
potential issues caused by busy functionality handling when
no busy functionality exist.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Merging the DT and ACPI specific probe functions into
dw8250_quirks. Those functions did not have that much code
any more and some of the quirks need to be shared. This
will also allow platforms without DT or ACPI to use the
driver.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This adds a flag "skip_autocfg" that the platforms that do
not have the ADDITIONAL_FEATURES implemented can use to skip
the port setup. It's then enough to call dw8250_setup_port
just from dw8250_probe based on that flag.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Instead of assigning the dma member in dw8250_probe_of and
dw8250_probe_acpi separately, assigning it in dw8250_probe.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This makes the properties available for all types of
platforms instead of just the ones using DT.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For convenience, adding separate pointer for the "port"
member of struct uart_8250_port that is being filled in the
probe function.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This allows earlycon to be used without needing to specify the I/O
address on the kernel command line, if linux,stdout-path is specified
in the chosen node.
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Earlycon allows to have an early debugging console that doesn't need
to be statically configured in the kernel config, like earlyprintk,
but is set up through the stdout-path DT property.

This allows to have the early debugging always built into the
kernel and enabled on demand without clashing between different boards
or architectures.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add support for debug communications channel based
hvc console for arm64 cpus.
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>
Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

hvc_instantiate() and hvc_alloc() return errors if they fail, so don't
ignore them.
Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Move ATMEL_MAX_UART from platform_data/atmel.h to atmel_serial.c as this is
the only file using it and it is common practise from tty/serial drivers to
define it directly in the driver file.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

If the 8250 driver is compiled as a module then
CONFIG_SERIAL_8250_MODULE is defined and not CONFIG_SERIAL_8250.

This results in all those code sections that require CONFIG_SERIAL_8250
to be defined are not included.

This patch fixes the situation and allows 8250 and of-serial to
be compiled as a module with the same functionality as when
compiled into the kernel.
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Use of_property_read_u32 instead of of_get_property with return value
checks and endianness conversion. Also remove the !CONFIG_OF
implementation of altera_uart_get_of_uartclk as of_property_read_u32
will return a non-zero value for !CONFIG_OF.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add these variants of the UART as compatible strings
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>

blah
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Enable the TX/RX FIFOs present on UARTs in Ingenic SoCs.
FIFO sizes vary per device so match these based on
the OF compatible string

Enabling the FIFOs permits much faster transfer with
lower CPU overhead.

Tested on Ingenic JZ4780 on the MIPS Ci20 Creator board
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The Ingenic UART is similar to a standard 16550, but hardware flow control
requires setting a couple of additional, non-standard bits in the MCR.

The non-standard "modem control enable" and "hardware flow control
mode" bits are set when writing to the MCR register, based
on whether the modem control interrupt is active.

Additionally the non-16550 compliant parts of the uart need to be
masked from higher layers.

Tested on Ingenic JZ4780 on MIPS Creator Ci20 board
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The driver has a I2C device id table that is used to create the modaliases
and also "sc16is7xx" is not a supported I2C id, so it's never used.
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The implementation of mux_console_device() is very similar to
uart_console_device(). Setting .data field in mux_console then we can
convert to use uart_console_device().
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Compare pointer-typed values to NULL rather than 0

The semantic patch that makes this change is available
in scripts/coccinelle/null/badzero.cocci.
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

So far, when interrupt occured in DMA mode, it was handled by terminating
DMA transfer and draining data remaining in RX FIFO. It worked well
until interrupt was caused by timeout, but the same interrupt can be
alse caused by special condition (eg. 'break'), which requires special
handling. In such case handling mechanism was the same - DMA transaction
was terminated and FIFO was drained, but any special conditions were
ingnored. Because of this in DMA mode there was no ability to use,
for example, Magic SysRq.

This patch fixes this problem by using s3c24xx_serial_rx_drain_fifo()
function instead of uart_rx_drain_fifo(), which does the same thing
(drains RX FIFO) plus checks UART status to detect special conditions
(such as 'break'). Thanks to this we have exactly the same UART status
handling in both DMA and PIO mode.

This change additionally simplifies RX handling code, as we no longer
need uart_rx_drain_fifo() function, so we can remove it.
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This patch introduces s3c24xx_serial_rx_drain_fifo() which reads data
from RX FIFO and writes it to tty buffer. It also checks for special
conditions (such as 'break') and handles it. This function has been
separated from s3c24xx_serial_rx_chars_pio() as it contains code which
can be used also in DMA mode.
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This label does nothing special and we don't need to have it anymore.
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This parameter is not used anywhere, so we can get rid of it.
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add support for obtaining DMA channel information from the device tree.

This requires switching from the legacy sh_dmae_slave structures with
hardcoded channel numbers and the corresponding filter function to:
  1. dma_request_slave_channel_compat(),
       - On legacy platforms, dma_request_slave_channel_compat() uses
	 the passed DMA channel numbers that originate from platform
	 device data,
       - On DT-based platforms, dma_request_slave_channel_compat() will
	 retrieve the information from DT.
  2. and the generic dmaengine_slave_config() configuration method,
     which requires filling in DMA register ports and slave bus widths.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Occasionally, DMA transaction completes _after_ DMA engine is stopped.
Verify if the transaction has not finished before forcing the engine to
stop and push the data
Signed-off-by: Muhammad Hamza Farooq <mfarooq@visteon.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

When DMA packet completion and timer expiry take place at the same time,
do not terminate the DMA engine, leading by submission of new
descriptors, as the DMA communication hasn't necessarily stopped here.
Signed-off-by: Muhammad Hamza Farooq <mfarooq@visteon.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

dmaengine_submit() will not start the DMA operation, it merely adds
it to the pending queue.  If the queue is no longer running, it won't be
restarted until dma_async_issue_pending() is called.
Signed-off-by: Muhammad Hamza Farooq <mfarooq@visteon.com>
[geert: Add more description]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Since the DMA engine is not stopped everytime rx_timer_fn is called, the
interrupts have to be redirected back to CPU only when incomplete DMA
transaction is handled
Signed-off-by: Muhammad Hamza Farooq <mfarooq@visteon.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This prevents DMA timer timeout that can trigger after the port has
been closed.
Signed-off-by: Aleksandar Mitev <amitev@visteon.com>
[geert: Move del_timer_sync() outside spinlock to avoid circular locking
        dependency between rx_timer_fn() and del_timer_sync()]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

There's no need to call sci_start_rx() from sci_request_dma() when DMA
setup fails, as sci_startup() will call sci_start_rx() anyway.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>