From 9636b755da7b498094bdf15b4ce9f6fd16995e4e Mon Sep 17 00:00:00 2001 From: Doug Anderson Date: Tue, 11 Oct 2011 17:05:43 -0700 Subject: [PATCH] tty/serial: Prevent drop of DCD on suspend for Tegra UARTs On Tegra UARTs (except UART1), the DTR / DCD / DSR lines are not externally accessible. Instead, the DTR line internally appears to be looped back to be the input to the DCD and DSR lines. The net effect of this is that when we drop DTR (like when we suspend), we'll see DCD drop too. ...and when we see DCD drop, we treat that as a hangup. In order to prevent this hangup from occurring at every sleep, we need to force DTR to remain high on Tegra UARTs. This patch uses the mcr_mask / mcr_force fields, which were originally added for the kludge ALPHA_KLUDGE_MCR. Using these fields does not prevent us from removing ALPHA_KLUDGE_MCR--we can just remove the "if" tests I have added and always init mcr_mask / mcr_force from the serial8250_config. NOTE: If we have people that are using UARTA on a Tegra and need to control DTR, we'll need to either add a separate port type for UARTA or we'll need to add some tegra-specific code to detect whether the DTR needs to be left high. Signed-off-by: Doug Anderson Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250.c | 14 ++++++++++++++ drivers/tty/serial/8250.h | 2 ++ 2 files changed, 16 insertions(+) diff --git a/drivers/tty/serial/8250.c b/drivers/tty/serial/8250.c index eeadf1b8e093..2b0a4b63c5f7 100644 --- a/drivers/tty/serial/8250.c +++ b/drivers/tty/serial/8250.c @@ -308,6 +308,8 @@ static const struct serial8250_config uart_config[] = { .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01 | UART_FCR_T_TRIG_01, .flags = UART_CAP_FIFO | UART_CAP_RTOIE, + .mcr_mask = ~UART_MCR_DTR, + .mcr_force = UART_MCR_DTR, }, [PORT_XR17D15X] = { .name = "XR17D15X", @@ -1229,6 +1231,10 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags) up->port.fifosize = uart_config[up->port.type].fifo_size; up->capabilities = uart_config[up->port.type].flags; up->tx_loadsz = uart_config[up->port.type].tx_loadsz; + if (!ALPHA_KLUDGE_MCR) { + up->mcr_mask = uart_config[up->port.type].mcr_mask; + up->mcr_force = uart_config[up->port.type].mcr_force; + } if (up->port.type == PORT_UNKNOWN) goto out; @@ -1987,6 +1993,10 @@ static int serial8250_startup(struct uart_port *port) up->port.fifosize = uart_config[up->port.type].fifo_size; up->tx_loadsz = uart_config[up->port.type].tx_loadsz; up->capabilities = uart_config[up->port.type].flags; + if (!ALPHA_KLUDGE_MCR) { + up->mcr_mask = uart_config[up->port.type].mcr_mask; + up->mcr_force = uart_config[up->port.type].mcr_force; + } up->mcr = 0; if (up->port.iotype != up->cur_iotype) @@ -2793,6 +2803,10 @@ serial8250_init_fixed_type_port(struct uart_8250_port *up, unsigned int type) up->port.fifosize = uart_config[type].fifo_size; up->capabilities = uart_config[type].flags; up->tx_loadsz = uart_config[type].tx_loadsz; + if (!ALPHA_KLUDGE_MCR) { + up->mcr_mask = uart_config[type].mcr_mask; + up->mcr_force = uart_config[type].mcr_force; + } } static void __init diff --git a/drivers/tty/serial/8250.h b/drivers/tty/serial/8250.h index 6edf4a6a22d4..1f7510051707 100644 --- a/drivers/tty/serial/8250.h +++ b/drivers/tty/serial/8250.h @@ -35,6 +35,8 @@ struct serial8250_config { unsigned short tx_loadsz; unsigned char fcr; unsigned int flags; + unsigned char mcr_mask; + unsigned char mcr_force; }; #define UART_CAP_FIFO (1 << 8) /* UART has FIFO */ -- 2.20.1