linux.git/drivers/tty/serial/meson_uart.c, branch v4.7

tty: serial: meson: Implement earlycon support

2016-04-30T16:26:55+00:00

Split off the bulk of the existing meson_serial_console_write()
implementation into meson_serial_port_write() for implementing
meson_serial_early_console_write().

Use "meson" as the earlycon driver name, courtesy of Nicolas.

Signed-off-by: Nicolas Saenz Julienne 
Acked-by: Carlo Caione 
Signed-off-by: Andreas Färber 
Signed-off-by: Greg Kroah-Hartman

tty: serial: meson: Add support for XTAL clock input

2016-02-15T01:39:36+00:00

Fix the baudrate calculation for 24 MHz XTAL clock found on gxbb platforms.

Signed-off-by: Andreas Färber 
Acked-by: Carlo Caione 
Signed-off-by: Greg Kroah-Hartman

ARM: meson: serial: check for tx-irq enabled in irq code

2015-12-14T03:59:48+00:00

Ensure that if the interrupt handler is entered then only try and do tx
work if the tx irq is enabled.

Signed-off-by: Ben Dooks 
Tested-by: Carlo Caione 
Signed-off-by: Greg Kroah-Hartman

ARM: meson: serial: ensure tx irq on if more work to do

2015-12-14T03:59:48+00:00

The tx_stop() call turns the interrupt off, but the tx_start() does not
check if the interrupt is enabled. Switch it back on if there is more
work to do.

Signed-off-by: Ben Dooks 
Tested-by: Carlo Caione 
Signed-off-by: Greg Kroah-Hartman

ARM: meson: serial: disable rx/tx irqs during console write

2015-12-14T03:59:48+00:00

As an attempt to stop issues with bad console output, ensure that both the
rx and tx interrupts are disabled during the console write to avoid any
problems with console and non-console being called together.

This should help with the SMP case as it should stop other cores being
signalled during the console write.

Signed-off-by: Ben Dooks 
Tested-by: Carlo Caione 
Signed-off-by: Greg Kroah-Hartman

ARM: meson: serial: use meson_uart_tx_empty() to wait for empty

2015-12-14T03:59:48+00:00

Use the meson_uart_tx_empty() instead of a direct read of the status
register. This is easier to read and will ensure the UART's transmit
state machine is idle when trying to update the baud rate.

Signed-off-by: Ben Dooks 
Tested-by: Carlo Caione 
Signed-off-by: Greg Kroah-Hartman

ARM: meson: serial: only disable tx irq on stop

2015-12-14T03:59:48+00:00

Since disabling the transmit state machine still allows characters to
be transmitted when written to the UART write FIFO, simply disable the
transmit interrupt when the UART port is stopped.

This has not shown an improvement with the console issues when running
systemd, but seems like it should be done.

Signed-off-by: Ben Dooks 
Reported-by: Edward Cragg 
Tested-by: Carlo Caione 
Signed-off-by: Greg Kroah-Hartman

ARM: meson: serial: ensure console port uart enabled

2015-12-14T03:59:48+00:00

Ensure the UART's transmitter is enabled when meson_console_putchar is
called. If not, then the console output is corrupt (the hardware seems
to try and send /something/ even if the TX is disabled).

This fixes corrupt console output on events such as trying to reboot the
system since the console tx may be called after drivers shutdown method has
been called.

Signed-off-by: Ben Dooks 
Reported-by: Edward Cragg 
Tested-by: Carlo Caione 
Signed-off-by: Greg Kroah-Hartman

ARM: meson: serial: tx_empty fails to check for transmitter busy

2015-12-14T03:59:48+00:00

The tx_empty() uart_op should only return empty if both the transmit fifo
and the transmit state-machine are both idle. Add a test for the hardware's
XMIT_BUSY flag.

Note, this is possibly related to an issue where the port is being shutdown
with paritally transmitted characters in it.

Signed-off-by: Ben Dooks 
Reported-by: Edward Cragg 
Tested-by: Carlo Caione 
Signed-off-by: Greg Kroah-Hartman

ARM: meson: serial: don't reset port on uart startup

2015-12-14T03:59:48+00:00

When the uart startup entry is called, do not reset the port as this
could cause issues with anything left in the FIFO from a previous operation
such as a console write. Move the hardware reset to probe time and simply
clear the errors before enabling the port.

This fixes the issue where the console could become corrupted as there
where characters left in the output or output fifo when a user process
such as systemd would open/close the uart to transmit characters.

For example, you get:
    [    3.252263] systemd[1]: Dete

instead of:
    [    3.338801] systemd[1]: Detected architecture arm.

Signed-off-by: Ben Dooks 
Tested-by: Carlo Caione 
Signed-off-by: Greg Kroah-Hartman