From ea5244e2af3b4813bf3d90ba6a6481d1a3c33d15 Mon Sep 17 00:00:00 2001 From: Joel Stanley Date: Tue, 2 May 2017 17:15:42 +0930 Subject: [PATCH] serial: 8250: Add flag so drivers can avoid THRE probe The probing of THRE irq behaviour assumes the other end will be reading bytes out of the buffer in order to probe the port at driver init. In some cases the other end cannot be relied upon to read these bytes, so provide a flag for them to skip this step. Bit 19 was chosen as the flags are a int and the top bits are taken. Acked-by: Benjamin Herrenschmidt Signed-off-by: Joel Stanley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_port.c | 2 +- include/linux/serial_core.h | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 09a65a3ec7f7..d5b6cee87801 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2229,7 +2229,7 @@ int serial8250_do_startup(struct uart_port *port) } } - if (port->irq) { + if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) { unsigned char iir1; /* * Test for UARTs that do not reassert THRE when the diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 64d892f1e5cd..1775500294bb 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -195,6 +195,7 @@ struct uart_port { #define UPF_NO_TXEN_TEST ((__force upf_t) (1 << 15)) #define UPF_MAGIC_MULTIPLIER ((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ ) +#define UPF_NO_THRE_TEST ((__force upf_t) (1 << 19)) /* Port has hardware-assisted h/w flow control */ #define UPF_AUTO_CTS ((__force upf_t) (1 << 20)) #define UPF_AUTO_RTS ((__force upf_t) (1 << 21)) -- 2.39.5