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authorLukas Wunner <lukas@wunner.de>2022-01-02 18:49:44 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-01-06 15:56:52 +0100
commit49a80424e3ec23ee2748f360348e167d5c748256 (patch)
treee3336d63bc696e17b2044a6d791902bffe0ab4c3
parente368cc656fd6d0075f1c3ab9676e2001451e3e04 (diff)
downloadlinux-49a80424e3ec23ee2748f360348e167d5c748256.tar.bz2
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>
-rw-r--r--drivers/tty/serial/amba-pl011.c7
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;