diff options
| author | Lukas Wunner <lukas@wunner.de> | 2022-01-02 18:49:44 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-01-06 15:56:52 +0100 |
| commit | 49a80424e3ec23ee2748f360348e167d5c748256 (patch) | |
| tree | e3336d63bc696e17b2044a6d791902bffe0ab4c3 /drivers/tty | |
| parent | e368cc656fd6d0075f1c3ab9676e2001451e3e04 (diff) | |
serial: pl011: Drop redundant DTR/RTS preservation on close/open
Commit d8d8ffa47783 ("amba-pl011: do not disable RTS during shutdown")
amended the PL011 serial driver to leave DTR/RTS polarity untouched on
tty close. That change made sense.
But the commit also added code to save DTR/RTS state to an internal
variable on tty close and restore it on tty open. That part of the
commit makes less sense: The driver has no ->pm() callback, so the uart
remains powered after tty close and automatically preserves register
state, including DTR/RTS.
Saving and restoring registers isn't the job of the ->startup() and
->shutdown() callbacks anyway. Rather, it should happen in ->pm().
Additionally, after pl011_startup() restores the state, the serial core
overrides it in uart_port_dtr_rts() if a baud rate has been set:
tty_port_open()
uart_port_activate()
uart_startup()
uart_port_startup()
pl011_startup() # restores DTR/RTS from uap->old_cr
tty_port_block_til_ready()
tty_port_raise_dtr_rts # if (C_BAUD(tty))
uart_dtr_rts()
uart_port_dtr_rts() # raises DTR/RTS
The serial core also overrides DTR/RTS on tty close in uart_shutdown()
if C_HUPCL(tty) is set. So a user-defined DTR/RTS polarity won't
survive a close/open cycle anyway, unless the user has set the baud rate
to zero and disabled hupcl on the tty.
Bottom line is, the code to save and restore DTR/RTS has no effect.
Remove it.
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/e22089ab49e6e78822c50c8c4db46bf3ee885623.1641129328.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/amba-pl011.c | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 7ca4f0da8309..1f1df46242f9 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -230,7 +230,6 @@ struct uart_amba_port { unsigned int im; /* interrupt mask */ unsigned int old_status; unsigned int fifosize; /* vendor-specific */ - unsigned int old_cr; /* state during shutdown */ unsigned int fixed_baud; /* vendor-set fixed baud rate */ char type[12]; bool rs485_tx_started; @@ -1805,8 +1804,8 @@ static int pl011_startup(struct uart_port *port) spin_lock_irq(&uap->port.lock); - /* restore RTS and DTR */ - cr = uap->old_cr & (UART011_CR_RTS | UART011_CR_DTR); + cr = pl011_read(uap, REG_CR); + cr &= UART011_CR_RTS | UART011_CR_DTR; cr |= UART01x_CR_UARTEN | UART011_CR_RXE; if (port->rs485.flags & SER_RS485_ENABLED) { @@ -1883,7 +1882,6 @@ static void pl011_disable_uart(struct uart_amba_port *uap) uap->port.status &= ~(UPSTAT_AUTOCTS | UPSTAT_AUTORTS); spin_lock_irq(&uap->port.lock); cr = pl011_read(uap, REG_CR); - uap->old_cr = cr; cr &= UART011_CR_RTS | UART011_CR_DTR; cr |= UART01x_CR_UARTEN | UART011_CR_TXE; pl011_write(cr, uap, REG_CR); @@ -2699,7 +2697,6 @@ static int pl011_setup_port(struct device *dev, struct uart_amba_port *uap, index = pl011_probe_dt_alias(index, dev); - uap->old_cr = 0; uap->port.dev = dev; uap->port.mapbase = mmiobase->start; uap->port.membase = base; |